Ebola virus disease epidemic
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Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a
viral hemorrhagic fever Viral hemorrhagic fevers (VHFs) are a diverse group of animal and human illnesses in which fever and hemorrhage are caused by a viral infection. VHFs may be caused by five distinct families of RNA viruses: the families ''Filoviridae'', ''Flavi ...
in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after becoming infected with the virus. The first symptoms are usually fever, sore throat, muscle pain, and
headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result ...
s. These are usually followed by vomiting, diarrhoea, rash and decreased liver and kidney function, at which point, some people begin to
bleed Bleeding usually means the leakage or loss of blood from the body. Bleeding, bleed, or bleeder may also refer to: *Bleed (printing), intentionally printing across the expected trim line or edge of the sheet *Bleed, or spill (audio), when audio fro ...
both internally and externally. The disease kills between 25% and 90% of those infected – about 50% on average. Death is often due to shock from fluid loss, and typically occurs between six and 16 days after the first symptoms appear. Early treatment of symptoms increases the survival rate considerably compared to late start. The virus spreads through direct contact with body fluids, such as blood from infected humans or other animals, or from contact with items that have recently been contaminated with infected body fluids. There have been no documented cases, either in nature or under laboratory conditions, of the disease spreading through the air between humans or other primates. After a person recovers from Ebola, their semen or
breast milk Breast milk (sometimes spelled as breastmilk) or mother's milk is milk produced by mammary glands located in the breast of a human female. Breast milk is the primary source of nutrition for newborns, containing fat, protein, carbohydrates ( lacto ...
may continue to carry the virus for anywhere between several weeks to several months. Fruit bats are believed to be the normal carrier in nature; they are able to spread the virus without being affected by it. The symptoms of Ebola may resemble those of several other diseases, including malaria,
cholera Cholera is an infection of the small intestine by some strains of the bacterium ''Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea that lasts a few days. Vomiting and ...
, typhoid fever,
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
and other viral hemorrhagic fevers. Diagnosis is confirmed by testing blood samples for the presence of viral
RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
, viral
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
or the virus itself. Control of outbreaks requires coordinated medical services and community engagement, including rapid detection, contact tracing of those exposed, quick access to laboratory services, care for those infected, and proper disposal of the dead through cremation or burial. Samples of body fluids and tissues from people with the disease should be handled with extreme caution. Prevention measures include wearing proper protective clothing and
washing hands Hand washing (or handwashing), also known as hand hygiene, is the act of cleaning one's hands with soap or handwash and water to remove viruses/bacteria/microorganisms, dirt, grease, or other harmful and unwanted substances stuck to the hand ...
when around a person with the disease, and limiting the spread of the disease from infected animals to humans – by wearing protective clothing while handling potentially infected
bushmeat Bushmeat is meat from wildlife species that are hunted for human consumption, most often referring to the meat of game in Africa. Bushmeat represents a primary source of animal protein and a cash-earning commodity for inhabitants of humid tropi ...
, and by cooking bushmeat thoroughly before eating it. An Ebola vaccine was approved in the United States in December 2019. While there is no approved treatment for Ebola , two treatments ( atoltivimab/maftivimab/odesivimab and
ansuvimab Ansuvimab, sold under the brand name Ebanga, is a monoclonal antibody medication for the treatment of ''Zaire ebolavirus'' (Ebolavirus) infection. The most common symptoms include fever, tachycardia (fast heart rate), diarrhea, vomiting, hypote ...
) are associated with improved outcomes. Supportive efforts also improve outcomes. These include oral rehydration therapy (drinking slightly sweetened and salty water) or giving
intravenous fluids Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...
, and treating symptoms. In October 2020, Atoltivimab/maftivimab/odesivimab (Inmazeb) was approved for medical use in the United States to treat the disease caused by ''Zaire ebolavirus''.


History and name

The disease was first identified in 1976, in two simultaneous outbreaks: one in
Nzara Nzara is a town in Western Equatoria State. It lies to the northwest of Yambio by road, and is 25 km (15m) from the border with the DR Congo. Nzara was industrial center of the Azande Scheme also known as, Equatoria Project Scheme during ...
(a town in South Sudan) and the other in Yambuku ( the Democratic Republic of the Congo), a village near the
Ebola River The Ebola River ( or ), also commonly known by its indigenous name Legbala, is the headstream of the Mongala River, a tributary of the Congo River, in northern Democratic Republic of the Congo. It is roughly in length. The name ''Ebola'' is a F ...
, from which the disease takes its name.
Ebola outbreaks This list of Ebola outbreaks records the known occurrences of Ebola virus disease, a highly infectious and acutely lethal Virus, viral disease that has afflicted humans and animals primarily in equatorial Africa. The pathogens responsible for ...
occur intermittently in tropical regions of
sub-Saharan Africa Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the List of sov ...
. Between 1976 and 2012, according to the World Health Organization, there were 24 outbreaks of Ebola resulting in a total of 2,387 cases, and 1,590 deaths. The largest Ebola outbreak to date was an epidemic in West Africa from December 2013 to January 2016, with cases and deaths. On 29 March 2016, it was declared to no longer be an emergency. Other outbreaks in Africa began in the Democratic Republic of the Congo in May 2017, and 2018. In July 2019, the World Health Organization declared the Congo Ebola outbreak a world health emergency.


Signs and symptoms


Onset

The length of time between exposure to the virus and the development of symptoms ( incubation period) is between 2 and 21 days, and usually between 4 and 10 days. However, recent estimates based on mathematical models predict that around 5% of cases may take longer than 21 days to develop. Symptoms usually begin with a sudden
influenza Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms ...
-like stage characterised by
fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...
, fever, weakness, decreased appetite,
muscular pain Myalgia (also called muscle pain and muscle ache in layman's terms) is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another lik ...
, joint pain, headache, and sore throat. The fever is usually higher than . This is often followed by nausea, vomiting, diarrhoea, abdominal pain, and sometimes hiccups. The combination of severe vomiting and diarrhoea often leads to severe dehydration. Next, shortness of breath and
chest pain Chest pain is pain or discomfort in the chest, typically the front of the chest. It may be described as sharp, dull, pressure, heaviness or squeezing. Associated symptoms may include pain in the shoulder, arm, upper abdomen, or jaw, along with n ...
may occur, along with swelling, headaches, and confusion. In about half of the cases, the skin may develop a maculopapular rash, a flat red area covered with small bumps, five to seven days after symptoms begin.


Bleeding

In some cases, internal and external bleeding may occur. This typically begins five to seven days after the first symptoms. All infected people show some decreased blood clotting. Bleeding from mucous membranes or from sites of needle punctures has been reported in 40–50% of cases. This may cause vomiting blood, coughing up of blood, or
blood in stool Blood in stool looks different depending on how early it enters the digestive tract—and thus how much digestive action it has been exposed to—and how much there is. The term can refer either to melena, with a black appearance, typically orig ...
. Bleeding into the skin may create
petechia A petechia () is a small red or purple spot (≤4 mm in diameter) that can appear on the skin, conjunctiva, retina, and Mucous membrane, mucous membranes which is caused by haemorrhage of capillaries. The word is derived from Italian , 'freckle,' ...
e, purpura, ecchymoses or
haematoma A hematoma, also spelled haematoma, or blood suffusion is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. A hematoma is b ...
s (especially around needle injection sites). Bleeding into the whites of the eyes may also occur. Heavy bleeding is uncommon; if it occurs, it is usually in the
gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...
. The incidence of bleeding into the gastrointestinal tract was reported to be ~58% in the 2001 outbreak in Gabon, but in the 2014–15 outbreak in the US it was ~18%, possibly due to improved prevention of
disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts o ...
.


Recovery or death

Recovery may begin between seven and 14 days after first symptoms. Death, if it occurs, follows typically six to sixteen days from first symptoms and is often due to shock from fluid loss. In general, bleeding often indicates a worse outcome, and blood loss may result in death. People are often in a
coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...
near the end of life. Those who survive often have ongoing muscular and joint pain,
liver inflammation Hepatitis is inflammation of the liver tissue. Some people or animals with hepatitis have no symptoms, whereas others develop yellow discoloration of the skin and whites of the eyes (jaundice), poor appetite, vomiting, tiredness, abdominal pain ...
, and decreased hearing, and may have continued tiredness, continued weakness, decreased appetite, and difficulty returning to pre-illness weight. Problems with vision may develop. It is recommended that survivors of EVD wear condoms for at least twelve months after initial infection or until the semen of a male survivor tests negative for Ebola virus on two separate occasions. Survivors develop
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
against Ebola that last at least 10 years, but it is unclear whether they are immune to additional infections.


Cause

EVD in humans is caused by four of six viruses of the genus '' Ebolavirus''. The four are
Bundibugyo virus The species ''Bundibugyo ebolavirus'' ( ) is the taxonomic home of one virus, Bundibugyo virus (BDBV), that forms filamentous virions and is closely related to the infamous Ebola virus (EBOV). The virus causes severe disease in humans in the form ...
(BDBV), Sudan virus (SUDV),
Taï Forest virus Taï is a town in southwestern Ivory Coast. It is a sub-prefecture of and the seat of Taï Department in Cavally Region, Montagnes District. Taï is also a commune. The town is between Taï National Park and the Cavally River. The river—which ...
(TAFV) and one simply called Ebola virus (EBOV, formerly Zaire Ebola virus). EBOV, species '' Zaire ebolavirus'', is the most dangerous of the known EVD-causing viruses, and is responsible for the largest number of outbreaks. The fifth and sixth viruses, Reston virus (RESTV) and Bombali virus (BOMV), are not thought to cause disease in humans, but have caused disease in other primates. All five viruses are closely related to
marburgvirus The genus ''Marburgvirus'' is the taxonomic home of ''Marburg marburgvirus'', whose members are the two known marburgviruses, Marburg virus (MARV) and Ravn virus (RAVV). Both viruses cause Marburg virus disease in humans and nonhuman primate ...
es.


Virology

Ebolaviruses contain single-stranded, non-infectious
RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
genomes. ''Ebolavirus'' genomes contain seven genes including
3'-UTR In molecular genetics, the three prime untranslated region (3′-UTR) is the section of messenger RNA (mRNA) that immediately follows the translation termination codon. The 3′-UTR often contains regulatory regions that post-transcriptionally ...
-''NP''-''VP35''-''VP40''-''GP''-''VP30''-''VP24''-''L''- 5'-UTR. The genomes of the five different ebolaviruses (BDBV, EBOV, RESTV, SUDV and TAFV) differ in sequence and the number and location of gene overlaps. As with all filoviruses, ebolavirus virions are filamentous particles that may appear in the shape of a shepherd's crook, of a "U" or of a "6," and they may be coiled, toroid or branched. In general, ebolavirions are 80 nanometers (nm) in width and may be as long as 14,000 nm. Their life cycle is thought to begin with a virion attaching to specific
cell-surface receptors The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...
such as C-type lectins, DC-SIGN, or integrins, which is followed by fusion of the viral envelope with cellular membranes. The virions taken up by the cell then travel to acidic endosomes and lysosomes where the viral envelope glycoprotein GP is cleaved. This processing appears to allow the virus to bind to cellular proteins enabling it to fuse with internal cellular membranes and release the viral
nucleocapsid A capsid is the protein shell of a virus, enclosing its genetic material. It consists of several oligomeric (repeating) structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may ...
. The ''Ebolavirus'' structural glycoprotein (known as GP1,2) is responsible for the virus' ability to bind to and infect targeted cells. The viral
RNA polymerase In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the ...
, encoded by the ''L'' gene, partially uncoats the nucleocapsid and transcribes the genes into positive-strand mRNAs, which are then
translated Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...
into structural and nonstructural proteins. The most abundant protein produced is the nucleoprotein, whose concentration in the host cell determines when L switches from gene transcription to genome replication. Replication of the viral genome results in full-length, positive-strand antigenomes that are, in turn, transcribed into genome copies of negative-strand virus progeny. Newly synthesised structural proteins and genomes self-assemble and accumulate near the inside of the cell membrane. Virions bud off from the cell, gaining their envelopes from the cellular membrane from which they bud. The mature progeny particles then infect other cells to repeat the cycle. The genetics of the Ebola virus are difficult to study because of EBOV's virulent characteristics.


Transmission

It is believed that between people, Ebola disease spreads only by direct contact with the blood or other body fluids of a person who has developed symptoms of the disease. Body fluids that may contain Ebola viruses include saliva, mucus, vomit, feces, sweat, tears, breast milk, urine and semen. The WHO states that only people who are very sick are able to spread Ebola disease in
saliva Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be ...
, and the virus has not been reported to be transmitted through sweat. Most people spread the virus through blood,
feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
and vomit. Entry points for the virus include the nose, mouth, eyes, open wounds, cuts and abrasions. Ebola may be spread through large droplets; however, this is believed to occur only when a person is very sick. This contamination can happen if a person is splashed with droplets. Contact with surfaces or objects contaminated by the virus, particularly needles and syringes, may also transmit the infection. The virus is able to survive on objects for a few hours in a dried state, and can survive for a few days within body fluids outside of a person. The Ebola virus may be able to persist for more than three months in the semen after recovery, which could lead to infections via
sexual intercourse Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetrat ...
. Virus persistence in semen for over a year has been recorded in a national screening programme. Ebola may also occur in the breast milk of women after recovery, and it is not known when it is safe to breastfeed again. The virus was also found in the eye of one patient in 2014, two months after it was cleared from his blood. Otherwise, people who have recovered are not infectious. The potential for widespread infections in countries with medical systems capable of observing correct medical isolation procedures is considered low. Usually when someone has symptoms of the disease, they are unable to travel without assistance. Dead bodies remain infectious; thus, people handling human remains in practices such as traditional burial rituals or more modern processes such as embalming are at risk. Of the cases of Ebola infections in Guinea during the 2014 outbreak, 69% are believed to have been contracted via unprotected (or unsuitably protected) contact with infected corpses during certain Guinean burial rituals. Health-care workers treating people with Ebola are at greatest risk of infection. The risk increases when they do not have appropriate protective clothing such as masks, gowns, gloves and eye protection; do not wear it properly; or handle contaminated clothing incorrectly. This risk is particularly common in parts of Africa where the disease mostly occurs and health systems function poorly. There has been transmission in hospitals in some African countries that reuse hypodermic needles. Some health-care centres caring for people with the disease do not have running water. In the United States the spread to two medical workers treating infected patients prompted criticism of inadequate training and procedures. Human-to-human transmission of EBOV through the air has not been reported to occur during EVD outbreaks, and airborne transmission has only been demonstrated in very strict laboratory conditions, and then only from pigs to
primates Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians (monkeys and apes, the latter including huma ...
, but not from primates to primates. Spread of EBOV by water, or food other than bushmeat, has not been observed. No spread by mosquitos or other insects has been reported. Other possible methods of transmission are being studied. Airborne transmission among humans is theoretically possible due to the presence of Ebola virus particles in saliva, which can be discharged into the air with a cough or sneeze, but observational data from previous epidemics suggests the actual risk of airborne transmission is low. A number of studies examining airborne transmission broadly concluded that transmission from pigs to primates could happen without direct contact because, unlike humans and primates, pigs with EVD get very high ebolavirus concentrations in their lungs, and not their bloodstream. Therefore, pigs with EVD can spread the disease through droplets in the air or on the ground when they sneeze or cough. By contrast, humans and other primates accumulate the virus throughout their body and specifically in their blood, but not very much in their lungs. It is believed that this is the reason researchers have observed pig to primate transmission without physical contact, but no evidence has been found of primates being infected without actual contact, even in experiments where infected and uninfected primates shared the same air.


Initial case

Although it is not entirely clear how Ebola initially spreads from animals to humans, the spread is believed to involve direct contact with an infected wild animal or fruit bat. Besides bats, other wild animals that are sometimes infected with EBOV include several species of monkeys such as baboons, great apes (
chimpanzee The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative th ...
s and gorillas), and duikers (a species of
antelope The term antelope is used to refer to many species of even-toed ruminant that are indigenous to various regions in Africa and Eurasia. Antelope comprise a wastebasket taxon defined as any of numerous Old World grazing and browsing hoofed mammals ...
). Animals may become infected when they eat fruit partially eaten by bats carrying the virus. Fruit production, animal behavior and other factors may trigger outbreaks among animal populations. Evidence indicates that both domestic dogs and pigs can also be infected with EBOV. Dogs do not appear to develop symptoms when they carry the virus, and pigs appear to be able to transmit the virus to at least some primates. Although some dogs in an area in which a human outbreak occurred had antibodies to EBOV, it is unclear whether they played a role in spreading the disease to people.


Reservoir

The natural reservoir for Ebola has yet to be confirmed; however, bats are considered to be the most likely candidate. Three types of fruit bats ('' Hypsignathus monstrosus'', '' Epomops franqueti'' and '' Myonycteris torquata'') were found to possibly carry the virus without getting sick. , whether other animals are involved in its spread is not known. Plants, arthropods, rodents, and birds have also been considered possible viral reservoirs. Bats were known to roost in the cotton factory in which the first cases of the 1976 and 1979 outbreaks were observed, and they have also been implicated in Marburg virus infections in 1975 and 1980. Of 24 plant and 19 vertebrate species experimentally inoculated with EBOV, only bats became infected. The bats displayed no clinical signs of disease, which is considered evidence that these bats are a reservoir species of EBOV. In a 2002–2003 survey of 1,030 animals including 679 bats from Gabon and the
Republic of the Congo The Republic of the Congo (french: République du Congo, ln, Republíki ya Kongó), also known as Congo-Brazzaville, the Congo Republic or simply either Congo or the Congo, is a country located in the western coast of Central Africa to the w ...
, immunoglobulin G (IgG) immune defense molecules indicative of Ebola infection were found in three bat species; at various periods of study, between 2.2 and 22.6% of bats were found to contain both RNA sequences and IgG molecules indicating Ebola infection. Antibodies against Zaire and Reston viruses have been found in fruit bats in Bangladesh, suggesting that these bats are also potential hosts of the virus and that the filoviruses are present in Asia. Between 1976 and 1998, in 30,000 mammals, birds, reptiles, amphibians and arthropods sampled from regions of EBOV outbreaks, no Ebola virus was detected apart from some genetic traces found in six rodents (belonging to the species ''
Mus setulosus Peters's mouse (''Mus setulosus'') is a species of rodent in the family Muridae. It is found in Benin, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Ethiopia, Gabon ...
'' and '' Praomys'') and one shrew (''
Sylvisorex ollula The greater forest shrew (''Sylvisorex ollula'') is a species of mammal in the family Soricidae found in Cameroon, the Central African Republic, the Republic of the Congo, Equatorial Guinea, Gabon, and Nigeria. Its natural habitat is subtropical ...
'') collected from the Central African Republic. However, further research efforts have not confirmed rodents as a reservoir. Traces of EBOV were detected in the carcasses of gorillas and chimpanzees during outbreaks in 2001 and 2003, which later became the source of human infections. However, the high rates of death in these species resulting from EBOV infection make it unlikely that these species represent a natural reservoir for the virus. Deforestation has been mentioned as a possible contributor to recent outbreaks, including the West African Ebola virus epidemic. Index cases of EVD have often been close to recently deforested lands.


Pathophysiology

Like other
filoviruses ''Filoviridae'' () is a family of single-stranded negative-sense RNA viruses in the order ''Mononegavirales''. Two members of the family that are commonly known are Ebola virus and Marburg virus. Both viruses, and some of their lesser known re ...
, EBOV replicates very efficiently in many
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
, producing large amounts of virus in monocytes,
macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...
s,
dendritic cell Dendritic cells (DCs) are antigen-presenting cells (also known as ''accessory cells'') of the mammalian immune system. Their main function is to process antigen material and present it on the cell surface to the T cells of the immune system. ...
s and other cells including liver cells,
fibroblast A fibroblast is a type of cell (biology), biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and plays a critical role in wound ...
s, and adrenal gland cells. Viral replication triggers high levels of inflammatory chemical signals and leads to a septic state. EBOV is thought to infect humans through contact with mucous membranes or skin breaks. After infection, endothelial cells (cells lining the inside of blood vessels), liver cells, and several types of immune cells such as macrophages, monocytes, and dendritic cells are the main targets of attack. Following infection, immune cells carry the virus to nearby
lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that inclu ...
s where further reproduction of the virus takes place. From there the virus can enter the bloodstream and
lymphatic system The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system, and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphatic or lymphoid o ...
and spread throughout the body. Macrophages are the first cells infected with the virus, and this infection results in programmed cell death. Other types of
white blood cell White blood cells, also called leukocytes or leucocytes, are the cell (biology), cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and de ...
s, such as lymphocytes, also undergo programmed cell death leading to an abnormally low concentration of lymphocytes in the blood. This contributes to the weakened immune response seen in those infected with EBOV. Endothelial cells may be infected within three days after exposure to the virus. The breakdown of endothelial cells leading to blood vessel injury can be attributed to EBOV
glycoprotein Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...
s. This damage occurs due to the synthesis of Ebola virus
glycoprotein Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...
(GP), which reduces the availability of specific integrins responsible for cell adhesion to the intercellular structure and causes liver damage, leading to improper clotting. The widespread bleeding that occurs in affected people causes swelling and shock due to loss of blood volume. The dysfunctional bleeding and clotting commonly seen in EVD has been attributed to increased activation of the extrinsic pathway of the
coagulation cascade Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...
due to excessive
tissue factor Tissue factor, also called platelet tissue factor, factor III, or CD142, is a protein encoded by the ''F3'' gene, present in subendothelial tissue and leukocytes. Its role in the clotting process is the initiation of thrombin formation from the ...
production by macrophages and monocytes. After infection, a secreted
glycoprotein Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...
, small soluble glycoprotein (sGP or GP) is synthesised. EBOV replication overwhelms protein synthesis of infected cells and the host immune defences. The GP forms a trimeric complex, which tethers the virus to the endothelial cells. The sGP forms a
dimeric protein In biochemistry, a protein dimer is a macromolecular complex formed by two protein monomers, or single proteins, which are usually non-covalently bound. Many macromolecules, such as proteins or nucleic acids, form dimers. The word ''dimer'' has ...
that interferes with the signalling of
neutrophils Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying in ...
, another type of white blood cell. This enables the virus to evade the immune system by inhibiting early steps of neutrophil activation.


Immune system evasion

Filoviral infection also interferes with proper functioning of the
innate immune system The innate, or nonspecific, immune system is one of the two main immunity strategies (the other being the adaptive immune system) in vertebrates. The innate immune system is an older evolutionary defense strategy, relatively speaking, and is the ...
. EBOV proteins blunt the human immune system's response to viral infections by interfering with the cells' ability to produce and respond to interferon proteins such as interferon-alpha,
interferon-beta The type-I interferons (IFN) are cytokines which play essential roles in inflammation, immunoregulation, tumor cells recognition, and T-cell responses. In the human genome, a cluster of thirteen functional IFN genes is located at the 9p21.3 cyto ...
, and interferon gamma. The VP24 and VP35 structural proteins of EBOV play a key role in this interference. When a cell is infected with EBOV, receptors located in the cell's cytosol (such as RIG-I and MDA5) or outside of the cytosol (such as Toll-like receptor 3 (TLR3),
TLR7 Toll-like receptor 7, also known as TLR7, is a protein that in humans is encoded by the ''TLR7'' gene. Orthologs are found in mammals and birds. It is a member of the toll-like receptor (TLR) family and detects single stranded RNA. Function T ...
,
TLR8 Toll-like receptor 8 is a protein that in humans is encoded by the ''TLR8'' gene. TLR8 has also been designated as CD288 (cluster of differentiation 288). It is a member of the toll-like receptor (TLR) family. Function TLR8 seems to function d ...
and TLR9) recognise infectious molecules associated with the virus. On TLR activation, proteins including
interferon regulatory factor 3 Interferon regulatory factor 3, also known as IRF3, is an interferon regulatory factor. Function IRF3 is a member of the interferon regulatory transcription factor (IRF) family. IRF3 was originally discovered as a homolog of IRF1 and IRF2. IR ...
and interferon regulatory factor 7 trigger a signalling cascade that leads to the expression of
type 1 interferon The type-I interferons (IFN) are cytokines which play essential roles in inflammation, immunoregulation, tumor cells recognition, and T-cell responses. In the human genome, a cluster of thirteen functional IFN genes is located at the 9p21.3 cyto ...
s. The type 1 interferons are then released and bind to the
IFNAR1 Interferon-alpha/beta receptor alpha chain is a protein that in humans is encoded by the ''IFNAR1'' gene. Function The protein encoded by this gene is a type I membrane protein that forms one of the two chains of a receptor for type I interfer ...
and IFNAR2 receptors expressed on the surface of a neighbouring cell. Once interferon has bound to its receptors on the neighbouring cell, the signalling proteins STAT1 and
STAT2 Signal transducer and activator of transcription 2 is a protein that in humans is encoded by the ''STAT2'' gene. It is a member of the STAT protein family. This protein is critical to the biological response of type I interferons (IFNs). STAT2 se ...
are activated and move to the cell's nucleus. This triggers the expression of interferon-stimulated genes, which code for proteins with antiviral properties. EBOV's V24 protein blocks the production of these antiviral proteins by preventing the STAT1 signalling protein in the neighbouring cell from entering the nucleus. The VP35 protein directly inhibits the production of interferon-beta. By inhibiting these immune responses, EBOV may quickly spread throughout the body.


Diagnosis

When EVD is suspected, travel, work history, and exposure to wildlife are important factors with respect to further diagnostic efforts.


Laboratory testing

Possible non-specific laboratory indicators of EVD include a
low platelet count Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients and ...
; an initially decreased white blood cell count followed by an increased white blood cell count; elevated levels of the liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST); and abnormalities in blood clotting often consistent with
disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts o ...
(DIC) such as a prolonged prothrombin time, partial thromboplastin time, and
bleeding time Bleeding time is a medical test done on someone to assess their platelets function. It involves making a patient bleed, then timing how long it takes for them to stop bleeding using a stopwatch or other suitable devices. The term template bleedin ...
. Filovirions such as EBOV may be identified by their unique filamentous shapes in cell cultures examined with
electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...
. The specific diagnosis of EVD is confirmed by isolating the virus, detecting its
RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
or proteins, or detecting
antibodies An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
against the virus in a person's blood. Isolating the virus by
cell culture Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This te ...
, detecting the viral RNA by polymerase chain reaction (PCR) and detecting proteins by enzyme-linked immunosorbent assay (ELISA) are methods best used in the early stages of the disease and also for detecting the virus in human remains. Detecting antibodies against the virus is most reliable in the later stages of the disease and in those who recover.
IgM antibodies Immunoglobulin M (IgM) is one of several isotypes of antibody (also known as immunoglobulin) that are produced by vertebrates. IgM is the largest antibody, and it is the first antibody to appear in the response to initial exposure to an antig ...
are detectable two days after symptom onset and
IgG antibodies Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG ...
can be detected six to 18 days after symptom onset. During an outbreak, isolation of the virus with cell culture methods is often not feasible. In field or mobile hospitals, the most common and sensitive diagnostic methods are real-time PCR and ELISA. In 2014, with new mobile testing facilities deployed in parts of Liberia, test results were obtained 3–5 hours after sample submission. In 2015, a rapid antigen test which gives results in 15 minutes was approved for use by WHO. It is able to confirm Ebola in 92% of those affected and rule it out in 85% of those not affected.


Differential diagnosis

Early symptoms of EVD may be similar to those of other diseases common in Africa, including malaria and
dengue fever Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. These may include a high fever, headache, vomiting, muscle and joint pains, and a characterist ...
. The symptoms are also similar to those of other viral haemorrhagic fevers such as Marburg virus disease, Crimean–Congo haemorrhagic fever, and Lassa fever. The complete
differential diagnosis In healthcare, a differential diagnosis (abbreviated DDx) is a method of analysis of a patient's history and physical examination to arrive at the correct diagnosis. It involves distinguishing a particular disease or condition from others that p ...
is extensive and requires consideration of many other infectious diseases such as typhoid fever,
shigellosis Shigellosis is an infection of the intestines caused by ''Shigella'' bacteria. Symptoms generally start one to two days after exposure and include diarrhea, fever, abdominal pain, and feeling the need to pass stools even when the bowels are emp ...
, rickettsial diseases,
cholera Cholera is an infection of the small intestine by some strains of the bacterium ''Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea that lasts a few days. Vomiting and ...
, sepsis,
borreliosis Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the ''Borrelia'' bacterium, which is spread by ticks in the genus ''Ixodes''. The most common sign of infection is an expanding red rash, known as erythema migran ...
, EHEC enteritis,
leptospirosis Leptospirosis is a blood infection caused by the bacteria ''Leptospira''. Signs and symptoms can range from none to mild (headaches, muscle pains, and fevers) to severe ( bleeding in the lungs or meningitis). Weil's disease, the acute, severe ...
, scrub typhus,
plague Plague or The Plague may refer to: Agriculture, fauna, and medicine *Plague (disease), a disease caused by ''Yersinia pestis'' * An epidemic of infectious disease (medical or agricultural) * A pandemic caused by such a disease * A swarm of pes ...
, Q fever, candidiasis, histoplasmosis, trypanosomiasis,
visceral In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...
leishmaniasis Leishmaniasis is a wide array of clinical manifestations caused by parasites of the trypanosome genus ''Leishmania''. It is generally spread through the bite of phlebotomine sandflies, ''Phlebotomus'' and ''Lutzomyia'', and occurs most freq ...
,
measles Measles is a highly contagious infectious disease caused by measles virus. Symptoms usually develop 10–12 days after exposure to an infected person and last 7–10 days. Initial symptoms typically include fever, often greater than , cough, ...
, and viral hepatitis among others. Non-infectious diseases that may result in symptoms similar to those of EVD include
acute promyelocytic leukaemia Acute promyelocytic leukemia (APML, APL) is a subtype of acute myeloid leukemia (AML), a cancer of the white blood cells. In APL, there is an abnormal accumulation of immature granulocytes called promyelocytes. The disease is characterized by a ...
,
haemolytic uraemic syndrome Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...
,
snake envenomation A snakebite is an injury caused by the bite of a snake, especially a venomous snake. A common sign of a bite from a venomous snake is the presence of two puncture wounds from the animal's fangs. Sometimes venom injection from the bite may occu ...
,
clotting factor Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanism o ...
deficiencies/platelet disorders, thrombotic thrombocytopenic purpura, hereditary haemorrhagic telangiectasia, Kawasaki disease, and warfarin poisoning.


Prevention


Vaccines

An Ebola vaccine,
rVSV-ZEBOV Recombinant vesicular stomatitis virus–Zaire Ebola virus (rVSV-ZEBOV), also known as Ebola Zaire vaccine live and sold under the brand name Ervebo, is an Ebola vaccine for adults that prevents Ebola caused by the Zaire ebolavirus. When used ...
, was approved in the United States in December 2019. It appears to be fully effective ten days after being given. It was studied in Guinea between 2014 and 2016. More than 100,000 people have been vaccinated against Ebola .


Infection control

Community awareness of the benefits on survival chances of admitting cases early is important for the infected and infection control


Caregivers

People who care for those infected with Ebola should wear protective clothing including masks, gloves, gowns and goggles. The U.S. Centers for Disease Control (CDC) recommend that the protective gear leaves no skin exposed. These measures are also recommended for those who may handle objects contaminated by an infected person's body fluids. In 2014, the CDC began recommending that medical personnel receive training on the proper suit-up and removal of personal protective equipment (PPE); in addition, a designated person, appropriately trained in biosafety, should be watching each step of these procedures to ensure they are done correctly. In Sierra Leone, the typical training period for the use of such safety equipment lasts approximately 12 days. In 2022 in Uganda, lighter personal protection equipment has become available as well as possibilities to monitor and communicate with patients from windows in the treatment tents until it is necessary to enter if e.g. a patient's oxygen levels drop.


Patients and household members

The infected person should be in barrier-isolation from other people. All equipment, medical waste, patient waste and surfaces that may have come into contact with body fluids need to be
disinfected A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than st ...
. During the 2014 outbreak, kits were put together to help families treat Ebola disease in their homes, which included protective clothing as well as
chlorine powder Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...
and other cleaning supplies. Education of caregivers in these techniques, and providing such barrier-separation supplies has been a priority of Doctors Without Borders.


Disinfection

Ebolaviruses can be eliminated with heat (heating for 30 to 60 minutes at 60 °C or boiling for five minutes). To disinfect surfaces, some lipid solvents such as some alcohol-based products, detergents, sodium hypochlorite (bleach) or
calcium hypochlorite Calcium hypochlorite is an inorganic compound with formula Ca(OCl)2. It is the main active ingredient of commercial products called bleaching powder, chlorine powder, or chlorinated lime, used for water treatment and as a bleaching agent. Thi ...
(bleaching powder), and other suitable disinfectants may be used at appropriate concentrations.


General population

Education of the general public about the risk factors for Ebola infection and of the protective measures individuals may take to prevent infection is recommended by the World Health Organization. These measures include avoiding direct contact with infected people and regular hand washing using soap and water.


Bushmeat

Bushmeat Bushmeat is meat from wildlife species that are hunted for human consumption, most often referring to the meat of game in Africa. Bushmeat represents a primary source of animal protein and a cash-earning commodity for inhabitants of humid tropi ...
, an important source of protein in the diet of some Africans, should be handled and prepared with appropriate protective clothing and thoroughly cooked before consumption. Some research suggests that an outbreak of Ebola disease in the wild animals used for consumption may result in a corresponding human outbreak. Since 2003, such animal outbreaks have been monitored to predict and prevent Ebola outbreaks in humans.


Corpses, burial

If a person with Ebola disease dies, direct contact with the body should be avoided. Certain
burial ritual Burial, also known as interment or inhumation, is a method of final disposition whereby a dead body is placed into the ground, sometimes with objects. This is usually accomplished by excavating a pit or trench, placing the deceased and objec ...
s, which may have included making various direct contacts with a dead body, require reformulation so that they consistently maintain a proper protective barrier between the dead body and the living. Social anthropologists may help find alternatives to traditional rules for burials.


Transport, travel, contact

Transportation crews are instructed to follow a certain isolation procedure, should anyone exhibit symptoms resembling EVD. , the WHO does not consider travel bans to be useful in decreasing spread of the disease. In October 2014, the CDC defined four risk levels used to determine the level of 21-day monitoring for symptoms and restrictions on public activities. In the United States, the CDC recommends that restrictions on public activity, including travel restrictions, are not required for the following defined risk levels: * having been in a country with widespread Ebola disease transmission and having no known exposure (low risk); or having been in that country more than 21 days ago (no risk) * encounter with a person showing symptoms; but not within three feet of the person with Ebola without wearing PPE; and no direct contact with body fluids * having had brief skin contact with a person showing symptoms of Ebola disease when the person was believed to be not very contagious (low risk) * in countries without widespread Ebola disease transmission: direct contact with a person showing symptoms of the disease while wearing PPE (low risk) * contact with a person with Ebola disease before the person was showing symptoms (no risk). The CDC recommends monitoring for the symptoms of Ebola disease for those both at "low risk" and at higher risk.


Laboratory

In laboratories where diagnostic testing is carried out, biosafety level 4-equivalent containment is required. Laboratory researchers must be properly trained in BSL-4 practices and wear proper PPE.


Isolation

Isolation refers to separating those who are sick from those who are not. Quarantine refers to separating those who may have been exposed to a disease until they either show signs of the disease or are no longer at risk. Quarantine, also known as enforced isolation, is usually effective in decreasing spread. Governments often quarantine areas where the disease is occurring or individuals who may transmit the disease outside of an initial area. In the United States, the law allows quarantine of those infected with ebolaviruses.


Contact tracing

Contact tracing is considered important to contain an outbreak. It involves finding everyone who had close contact with infected individuals and monitoring them for signs of illness for 21 days. If any of these contacts comes down with the disease, they should be isolated, tested and treated. Then the process is repeated, tracing the contacts' contacts.


Management

two treatments ( atoltivimab/maftivimab/odesivimab and
ansuvimab Ansuvimab, sold under the brand name Ebanga, is a monoclonal antibody medication for the treatment of ''Zaire ebolavirus'' (Ebolavirus) infection. The most common symptoms include fever, tachycardia (fast heart rate), diarrhea, vomiting, hypote ...
) are associated with improved outcomes. The U.S. Food and Drug Administration (FDA) advises people to be careful of advertisements making unverified or fraudulent claims of benefits supposedly gained from various anti-Ebola products. In October 2020, the U.S. Food and Drug Administration (FDA) approved atoltivimab/maftivimab/odesivimab with an
indication Indication may refer to: * A synonym for sign * Human interface, highlighting the single object pointed to as a cursor is moved, without any other user action such as clicking, is indication * Indication (medicine). A valid reason to use a certain ...
for the treatment of infection caused by ''Zaire ebolavirus''.


Standard support

Treatment is primarily supportive in nature. Early supportive care with rehydration and symptomatic treatment improves survival. Rehydration may be via the oral or
intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...
route. These measures may include pain management, and treatment for nausea, fever, and anxiety. The World Health Organization (WHO) recommends avoiding aspirin or
ibuprofen Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that is used for treating pain, fever, and inflammation. This includes painful menstrual periods, migraines, and rheumatoid arthritis. It may also be used to close a patent ductus arte ...
for pain management, due to the risk of bleeding associated with these medications. Blood products such as packed red blood cells, platelets, or fresh frozen plasma may also be used. Other regulators of coagulation have also been tried including
heparin Heparin, also known as unfractionated heparin (UFH), is a medication and naturally occurring glycosaminoglycan. Since heparins depend on the activity of antithrombin, they are considered anticoagulants. Specifically it is also used in the treatm ...
in an effort to prevent
disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts o ...
and clotting factors to decrease bleeding. Antimalarial medications and antibiotics are often used before the diagnosis is confirmed, though there is no evidence to suggest such treatment helps. Several experimental treatments are being studied. Where hospital care is not possible, the WHO's guidelines for home care have been relatively successful. Recommendations include using towels soaked in a bleach solution when moving infected people or bodies and also applying bleach on stains. It is also recommended that the caregivers wash hands with bleach solutions and cover their mouth and nose with a cloth.


Intensive care

Intensive care is often used in the developed world. This may include maintaining blood volume and electrolytes (salts) balance as well as treating any bacterial infections that may develop.
Dialysis Dialysis may refer to: *Dialysis (chemistry), a process of separating molecules in solution **Electrodialysis, used to transport salt ions from one solution to another through an ion-exchange membrane under the influence of an applied electric pote ...
may be needed for kidney failure, and
extracorporeal membrane oxygenation Extracorporeal membrane oxygenation (ECMO), also known as extracorporeal life support (ECLS), is an extracorporeal technique of providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequat ...
may be used for lung dysfunction.


Prognosis

EVD has a risk of death in those infected of between 25% and 90%. , the average risk of death among those infected is 50%. The highest risk of death was 90% in the 2002–2003
Republic of the Congo The Republic of the Congo (french: République du Congo, ln, Republíki ya Kongó), also known as Congo-Brazzaville, the Congo Republic or simply either Congo or the Congo, is a country located in the western coast of Central Africa to the w ...
outbreak. Early admission significantly increases survival rates Death, if it occurs, follows typically six to sixteen days after symptoms appear and is often due to low blood pressure from fluid loss. Early supportive care to prevent dehydration may reduce the risk of death. If an infected person survives, recovery may be quick and complete. Prolonged cases are often complicated by the occurrence of long-term problems, such as inflammation of the testicles,
joint pains Arthralgia (from Greek ''arthro-'', joint + ''-algos'', pain) literally means ''joint pain''. Specifically, arthralgia is a symptom of injury, infection, illness (in particular arthritis), or an allergic reaction to medication. According to MeSH, ...
, fatigue, hearing loss, mood and sleep disturbances,
muscular pain Myalgia (also called muscle pain and muscle ache in layman's terms) is the medical term for muscle pain. Myalgia is a symptom of many diseases. The most common cause of acute myalgia is the overuse of a muscle or group of muscles; another lik ...
, abdominal pain, menstrual abnormalities,
miscarriage Miscarriage, also known in medical terms as a spontaneous abortion and pregnancy loss, is the death of an embryo or fetus before it is able to survive independently. Miscarriage before 6 weeks of gestation is defined by ESHRE as biochemical lo ...
s,
skin peeling Desquamation occurs when the outermost layer of a tissue, such as the skin, is shed. The term is . Physiologic desquamation Keratinocytes are the predominant cells of the epidermis, the outermost layer of the skin. Living keratinocytes reside in ...
, or hair loss. Inflammation and swelling of the uveal layer of the eye is the most common eye complication in survivors of Ebola virus disease. Eye symptoms, such as light sensitivity, excess tearing, and vision loss have been described. Ebola can stay in some body parts like the eyes, breasts, and testicles after infection. Sexual transmission after recovery has been suspected. If sexual transmission occurs following recovery it is believed to be a rare event. One case of a condition similar to
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
has been reported many months after recovery, . A study of 44 survivors of the Ebola virus in Sierra Leone reported musculoskeletal pain in 70%, headache in 48%, and eye problems in 14%.


Epidemiology

The disease typically occurs in outbreaks in tropical regions of
Sub-Saharan Africa Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the List of sov ...
. From 1976 (when it was first identified) through 2013, the WHO reported 2,387 confirmed cases with 1,590 overall fatalities. The largest outbreak to date was the Ebola virus epidemic in West Africa, which caused a large number of deaths in
Guinea Guinea ( ),, fuf, 𞤘𞤭𞤲𞤫, italic=no, Gine, wo, Gine, nqo, ߖߌ߬ߣߍ߫, bm, Gine officially the Republic of Guinea (french: République de Guinée), is a coastal country in West Africa. It borders the Atlantic Ocean to the we ...
, Sierra Leone, and
Liberia Liberia (), officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to Liberia–Sierra Leone border, its northwest, Guinea to its north, Ivory Coast to its east, and the Atlantic Ocean ...
.


1976


Sudan

The first known outbreak of EVD was identified only after the fact. It occurred between June and November 1976, in Nzara, South Sudan (then part of
Sudan Sudan ( or ; ar, السودان, as-Sūdān, officially the Republic of the Sudan ( ar, جمهورية السودان, link=no, Jumhūriyyat as-Sūdān), is a country in Northeast Africa. It shares borders with the Central African Republic t ...
), and was caused by Sudan virus (SUDV). The Sudan outbreak infected 284 people and killed 151. The first identifiable case in Sudan occurred on 27 June in a storekeeper in a cotton factory in
Nzara Nzara is a town in Western Equatoria State. It lies to the northwest of Yambio by road, and is 25 km (15m) from the border with the DR Congo. Nzara was industrial center of the Azande Scheme also known as, Equatoria Project Scheme during ...
, who was hospitalised on 30 June and died on 6 July. Although the WHO medical staff involved in the Sudan outbreak knew that they were dealing with a heretofore unknown disease, the actual "positive identification" process and the naming of the virus did not occur until some months later in Zaire.


Zaire

On 26 August 1976, the second outbreak of EVD began in Yambuku, a small rural village in Mongala District in northern Zaire (now known as the Democratic Republic of the Congo). This outbreak was caused by EBOV, formerly designated ''Zaire ebolavirus'', a different member of the genus ''Ebolavirus'' than in the first Sudan outbreak. The first person infected with the disease was the village school's headmaster
Mabalo Lokela Yambuku is a small village in Mongala Province in northern Democratic Republic of the Congo. It was the center of the first documented outbreak of Ebola virus disease, in 1976, with the World Health Organization identifying a man from Yambuku as th ...
, who began displaying symptoms on 26 August 1976. Lokela had returned from a trip to Northern Zaire near the border of the Central African Republic, after visiting the
Ebola River The Ebola River ( or ), also commonly known by its indigenous name Legbala, is the headstream of the Mongala River, a tributary of the Congo River, in northern Democratic Republic of the Congo. It is roughly in length. The name ''Ebola'' is a F ...
between 12 and 22 August. He was originally believed to have malaria and was given quinine. However, his symptoms continued to worsen, and he was admitted to Yambuku Mission Hospital on 5 September. Lokela died on 8 September 14 days after he began displaying symptoms. Soon after Lokela's death, others who had been in contact with him also died, and people in Yambuku began to panic. The country's Minister of Health and Zaire President
Mobutu Sese Seko Mobutu Sese Seko Kuku Ngbendu Wa Za Banga (; born Joseph-Désiré Mobutu; 14 October 1930 – 7 September 1997) was a Congolese politician and military officer who was the president of Zaire from 1965 to 1997 (known as the Democratic Republic o ...
declared the entire region, including Yambuku and the country's capital,
Kinshasa Kinshasa (; ; ln, Kinsásá), formerly Léopoldville ( nl, Leopoldstad), is the capital and largest city of the Democratic Republic of the Congo. Once a site of fishing and trading villages situated along the Congo River, Kinshasa is now one o ...
, a quarantine zone. No-one was permitted to enter or leave the area, and roads, waterways, and airfields were placed under martial law. Schools, businesses and social organisations were closed. The initial response was led by Congolese doctors, including
Jean-Jacques Muyembe-Tamfum Jean-Jacques Muyembe is a Congolese microbiologist. He is the general director of the Democratic Republic of the Congo Institut National pour la Recherche Biomedicale (''INRB''). He was part of team at the Yambuku Catholic Mission Hospital that ...
, one of the discoverers of Ebola. Muyembe took a blood sample from a Belgian nun; this sample would eventually be used by Peter Piot to identify the previously unknown Ebola virus. Muyembe was also the first scientist to come into direct contact with the disease and survive. Researchers from the Centers for Disease Control and Prevention (CDC), including Piot, co-discoverer of Ebola, later arrived to assess the effects of the outbreak, observing that "the whole region was in panic." Piot concluded that Belgian nuns had inadvertently started the epidemic by giving unnecessary vitamin injections to pregnant women without sterilizing the syringes and needles. The outbreak lasted 26 days and the quarantine lasted two weeks. Researchers speculated that the disease disappeared due to the precautions taken by locals, the quarantine of the area, and discontinuing of the injections. During this outbreak, Ngoy Mushola recorded the first clinical description of EVD in Yambuku, where he wrote the following in his daily log: "The illness is characterised with a high temperature of about ,
haematemesis Hematemesis is the vomiting of blood. It is always an important sign. It can be confused with hemoptysis (coughing up blood) or epistaxis (nosebleed), which are more common. The source is generally the upper gastrointestinal tract, typically abo ...
, diarrhoea with blood, retrosternal abdominal pain, prostration with 'heavy' articulations, and rapid evolution death after a mean of three days." The virus responsible for the initial outbreak, first thought to be the
Marburg virus Marburg virus (MARV) is a hemorrhagic fever virus of the ''Filoviridae'' family of viruses and a member of the species '' Marburg marburgvirus'', genus ''Marburgvirus''. It causes Marburg virus disease in primates, a form of viral hemorrhagic f ...
, was later identified as a new type of virus related to the genus ''
Marburgvirus The genus ''Marburgvirus'' is the taxonomic home of ''Marburg marburgvirus'', whose members are the two known marburgviruses, Marburg virus (MARV) and Ravn virus (RAVV). Both viruses cause Marburg virus disease in humans and nonhuman primate ...
''. Virus strain samples isolated from both outbreaks were named "Ebola virus" after the
Ebola River The Ebola River ( or ), also commonly known by its indigenous name Legbala, is the headstream of the Mongala River, a tributary of the Congo River, in northern Democratic Republic of the Congo. It is roughly in length. The name ''Ebola'' is a F ...
, near the first-identified viral outbreak site in Zaire. Reports conflict about who initially coined the name: either Karl Johnson of the American CDC team or Belgian researchers. Subsequently, a number of other cases were reported, almost all centred on the Yambuku mission hospital or close contacts of another case. In all, 318 cases and 280 deaths (an 88% fatality rate) occurred in Zaire. Although the two outbreaks were at first believed connected, scientists later realised that they were caused by two distinct ebolaviruses, SUDV and EBOV.


1995–2014

The second major outbreak occurred in Zaire (now the Democratic Republic of the Congo, DRC), in 1995, affecting 315 and killing 254. In 2000, Uganda had an outbreak infecting 425 and killing 224; in this case, the Sudan virus was found to be the Ebola species responsible for the outbreak. In 2003, an outbreak in the DRC infected 143 and killed 128, a 90% death rate, the highest of a genus ''Ebolavirus'' outbreak to date. In 2004, a Russian scientist died from Ebola after sticking herself with an infected needle. Between April and August 2007, a fever epidemic in a four-village region of the DRC was confirmed in September to have been cases of Ebola. Many people who attended the recent funeral of a local village chief died. The 2007 outbreak eventually infected 264 individuals and killed 187. On 30 November 2007, the Uganda Ministry of Health confirmed an outbreak of Ebola in the Bundibugyo District in Western Uganda. After confirming samples tested by the United States National Reference Laboratories and the Centers for Disease Control, the World Health Organization (WHO) confirmed the presence of a new species of genus ''Ebolavirus'', which was tentatively named Bundibugyo. The WHO reported 149 cases of this new strain and 37 of those led to deaths. The WHO confirmed two small outbreaks in Uganda in 2012, both caused by the Sudan variant. The first outbreak affected seven people, killing four, and the second affected 24, killing 17. On 17 August 2012, the Ministry of Health of the DRC reported an outbreak of the Ebola-Bundibugyo variant in the eastern region. Other than its discovery in 2007, this was the only time that this variant has been identified as responsible for an outbreak. The WHO revealed that the virus had sickened 57 people and killed 29. The probable cause of the outbreak was tainted
bush meat Bushmeat is meat from wildlife species that are hunted for human consumption, most often referring to the meat of game in Africa. Bushmeat represents a primary source of animal protein and a cash-earning commodity for inhabitants of humid tro ...
hunted by local villagers around the towns of
Isiro Isiro (pronounced ) is the capital of Haut-Uele Province in the northeastern part of the Democratic Republic of the Congo. It lies between the equatorial forest and the savannah and its main resource is coffee. Isiro's population is estimated a ...
and Viadana. In 2014, an outbreak occurred in the DRC. Genome-sequencing showed that this outbreak was not related to the 2014–15 West Africa Ebola virus outbreak, but was the same EBOV species, the Zaire species. It began in August 2014, and was declared over in November with 66 cases and 49 deaths. This was the 7th outbreak in the DRC, three of which occurred during the period when the country was known as Zaire.


2013–2016 West Africa

In March 2014, the World Health Organization (WHO) reported a major Ebola outbreak in
Guinea Guinea ( ),, fuf, 𞤘𞤭𞤲𞤫, italic=no, Gine, wo, Gine, nqo, ߖߌ߬ߣߍ߫, bm, Gine officially the Republic of Guinea (french: République de Guinée), is a coastal country in West Africa. It borders the Atlantic Ocean to the we ...
, a West African nation. Researchers traced the outbreak to a one-year-old child who died in December 2013. The disease rapidly spread to the neighbouring countries of
Liberia Liberia (), officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to Liberia–Sierra Leone border, its northwest, Guinea to its north, Ivory Coast to its east, and the Atlantic Ocean ...
and Sierra Leone. It was the largest Ebola outbreak ever documented, and the first recorded in the region. On 8 August 2014, the WHO declared the epidemic an international public health emergency. Urging the world to offer aid to the affected regions, its Director-General said, "Countries affected to date simply do not have the capacity to manage an outbreak of this size and complexity on their own. I urge the international community to provide this support on the most urgent basis possible." By mid-August 2014, Doctors Without Borders reported the situation in Liberia's capital, Monrovia, was "catastrophic" and "deteriorating daily". They reported that fears of Ebola among staff members and patients had shut down much of the city's health system, leaving many people without medical treatment for other conditions. In a 26 September statement, WHO said, "The Ebola epidemic ravaging parts of West Africa is the most severe acute public health emergency seen in modern times. Never before in recorded history has a biosafety level four pathogen infected so many people so quickly, over such a broad geographical area, for so long." Intense contact tracing and strict isolation largely prevented further spread of the disease in the countries that had imported cases. , suspected cases and deaths were reported; however, the WHO said that these numbers may be underestimated. Because they work closely with the body fluids of infected patients, healthcare workers were especially vulnerable to infection; in August 2014, the WHO reported that 10% of the dead were healthcare workers. In September 2014, it was estimated that the countries' capacity for treating Ebola patients was insufficient by the equivalent of 2,122 beds; by December there were a sufficient number of beds to treat and isolate all reported Ebola cases, although the uneven distribution of cases was causing serious shortfalls in some areas. On 28 January 2015, the WHO reported that for the first time since the week ending 29 June 2014, there had been fewer than 100 new confirmed cases reported in a week in the three most-affected countries. The response to the epidemic then moved to a second phase, as the focus shifted from slowing transmission to ending the epidemic. On 8 April 2015, the WHO reported only 30 confirmed cases, the lowest weekly total since the third week of May 2014. On 29 December 2015, 42 days after the last person tested negative for a second time, Guinea was declared free of Ebola transmission. At that time, a 90-day period of heightened surveillance was announced by that agency. "This is the first time that all three countries – Guinea, Liberia and Sierra Leone – have stopped the original chains of transmission ...", the organisation stated in a news release. A new case was detected in Sierra Leone on 14 January 2016. However, the outbreak was declared no longer an emergency on 29 March 2016.


2014 spread outside West Africa

On 19 September, Eric Duncan flew from his native Liberia to Texas; five days later he began showing symptoms and visited a hospital but was sent home. His condition worsened and he returned to the hospital on 28 September, where he died on 8 October. Health officials confirmed a diagnosis of Ebola on 30 September – the first case in the United States. In early October, Teresa Romero, a 44-year-old Spanish nurse, contracted Ebola after caring for a priest who had been repatriated from West Africa. This was the first transmission of the virus to occur outside Africa. Romero tested negative for the disease on 20 October, suggesting that she may have recovered from Ebola infection. On 12 October, the Centers for Disease Control and Prevention (CDC) confirmed that a nurse in Texas,
Nina Pham Four laboratory-confirmed cases of Ebola virus disease (commonly known as "Ebola") occurred in the United States in 2014. Eleven cases were reported, including these four cases and seven cases medically evacuated from other countries. The first ...
, who had treated Duncan tested positive for the Ebola virus, the first known case of transmission in the United States. On 15 October, a second Texas health-care worker who had treated Duncan was confirmed to have the virus. Both of these people recovered. An unrelated case involved a doctor in New York City, who returned to the United States from Guinea after working with Médecins Sans Frontières and tested positive for Ebola on 23 October. The person recovered and was discharged from Bellevue Hospital on 11 November. On 24 December 2014, a laboratory in Atlanta, Georgia reported that a technician had been exposed to Ebola. On 29 December 2014, Pauline Cafferkey, a British nurse who had just returned to Glasgow from Sierra Leone, was diagnosed with Ebola at Glasgow's Gartnavel General Hospital. After initial treatment in Glasgow, she was transferred by air to RAF Northolt, then to the specialist
high-level isolation unit In hospitals and other medical facilities, an isolation ward is a separate ward used to isolate patients with infectious diseases. Several wards for individual patients are usually placed together in an isolation unit. Design In an isolation un ...
at the
Royal Free Hospital The Royal Free Hospital (also known simply as the Royal Free) is a major teaching hospital in the Hampstead area of the London Borough of Camden. The hospital is part of the Royal Free London NHS Foundation Trust, which also runs services at Barn ...
in London for longer-term treatment.


2017 Democratic Republic of the Congo

On 11 May 2017, the DRC Ministry of Public Health notified the WHO about an outbreak of Ebola. Four people died, and four people survived; five of these eight cases were laboratory-confirmed. A total of 583 contacts were monitored. On 2 July 2017, the WHO declared the end of the outbreak.


2018 Équateur province

On 14 May 2018, the World Health Organization reported that "the Democratic Republic of Congo reported 39 suspected, probable or confirmed cases of Ebola between 4 April and 13 May, including 19 deaths." Some 393 people identified as contacts of Ebola patients were being followed up. The outbreak centred on the Bikoro, Iboko, and Wangata areas in Equateur province, including in the large city of Mbandaka. The DRC Ministry of Public Health approved the use of an experimental vaccine. On 13 May 2018, WHO Director-General Tedros Adhanom Ghebreyesus visited Bikoro. Reports emerged that maps of the area were inaccurate, not so much hampering medical providers as epidemiologists and officials trying to assess the outbreak and containment efforts. The 2018 outbreak in the DRC was declared over on 24 July 2018.


2018–2020 Kivu

On 1 August 2018, the world's 10th Ebola outbreak was declared in North Kivu province of the Democratic Republic of the Congo. It was the first Ebola outbreak in a military conflict zone, with thousands of refugees in the area. By November 2018, nearly 200 Congolese had died of Ebola, about half of them from the city of Beni, where armed groups are fighting over the region's mineral wealth, impeding medical relief efforts. By March 2019, this became the second largest Ebola outbreak ever recorded, with more than 1,000 cases and insecurity continuing to be the major resistance to providing an adequate response. , the WHO reported 2025 confirmed and probable cases with 1357 deaths. In June 2019, two people died of Ebola in neighbouring Uganda. In July 2019, an infected man travelled to Goma, home to more than two million people. One week later, on 17 July 2019, the WHO declared the Ebola outbreak a global health emergency, the fifth time such a declaration has been made by the organisation. A government spokesman said that half of the Ebola cases are unidentified, and he added that the current outbreak could last up to three years. On 25 June 2020, the second biggest EVD outbreak ever was declared over.


2020 Équateur province

On 1 June 2020, the Congolese health ministry announced a new DRC outbreak of Ebola in Mbandaka, Équateur Province, a region along the Congo River. Genome sequencing suggests that this outbreak, the 11th outbreak since the virus was first discovered in the country in 1976, is unrelated to the one in North Kivu Province or the previous outbreak in the same area in 2018. It was reported that six cases had been identified; four of the people had died. It is expected that more people will be identified as surveillance activities increase. By 15 June the case count had increased to 17 with 11 deaths, with more than 2,500 people having been vaccinated. The 11th EVD outbreak was officially declared over on 19 November 2020. By the time the Équateur outbreak ended, it had 130 confirmed cases with 75 recoveries and 55 deaths.


2021


North Kivu

On 7 February 2021, the Congolese health ministry announced a new case of Ebola near Butembo, North Kivu detected a day before. The case was a 42-year-old woman who had symptoms of Ebola in Biena on 1 February 2021. A few days after, she died in a hospital in Butembo. The WHO said that more than 70 people with contact with the woman had been tracked. On 11 February 2021, another woman who had contact with the previous woman died in the same town, and the number of traced contacts increased to 100. A day after, a third case was detected in Butembo. On 3 May 2021, the 12th EVD outbreak was declared over, resulting in 12 cases and six deaths. Heightened surveillance will continue for 90 days after the declaration, in case of resurgence.


Guinea

In February 2021, Dr Sakoba Keita, head of Guinea's national health agency confirmed that three people had died of Ebola in the south-eastern region near the city of Nzérékoré. A further five people also tested positive. Keita also confirmed more testing was underway, and attempts to trace and isolate further cases had begun. On 14 February, the Guinean government declared an Ebola epidemic. The outbreak may have started following reactivation of a latent case in a survivor of an earlier outbreak. As of 4 May 2021, 23 cases were reported, with no new cases or deaths since 3 April 2021. A 42-day countdown period was started on 8 May 2021, and on 19 June, the outbreak was declared over.


Ivory Coast

On 14 August 2021, The Ministry of Health of
Cote d’Ivoire Ivory Coast, also known as Côte d'Ivoire, officially the Republic of Côte d'Ivoire, is a country on the southern coast of West Africa. Its capital is Yamoussoukro, in the centre of the country, while its largest city and economic centre is ...
confirmed the country's first case of Ebola since 1994. This came after the Institut Pasteur in Cote d'Ivoire confirmed the Ebola Virus Disease in samples collected from a patient, who was hospitalized in the commercial capital of Abidjan, after arriving from Guinea. However, on 31 August 2021, the WHO found that, after further tests in a laboratory in Lyon, the patient did not have Ebola. The cause of her disease is still being analyzed.


2022

On 23 April 2022, a case of Ebola was confirmed in the DRC in the Equateur province. The case was a 31-year-old man whose symptoms began on 5 April, but did not seek treatment for over a week. On 21 April, he was admitted to an Ebola treatment centre and died later that day. By 24 May 2022, there were 5 recorded deaths in the DRC. On 15 August, the fifth case was buried, and the outbreak was declared over, 42 days after, on 4 July 2022. In September 2022, Uganda reported 7 cases infected with the Ebola Sudan strain, but by mid-October the count had increased to 63. In November 2022 (present), the outbreak in Uganda continued - still without a vaccine.


Society and culture


Weaponisation

''Ebolavirus'' is classified as a biosafety level 4 agent, as well as a Category A bioterrorism agent by the Centers for Disease Control and Prevention. It has the potential to be weaponised for use in biological warfare, and was investigated by
Biopreparat The All-Union Science Production Association Biopreparat (russian: Биопрепарат, p=bʲɪəprʲɪpɐˈrat, lit: "biological preparation") was the Soviet agency created in April 1974, which spearheaded the largest and most sophisticated ...
for such use, but might be difficult to prepare as a weapon of mass destruction because the virus becomes ineffective quickly in open air. Fake emails pretending to be Ebola information from the WHO or the Mexican government have, in 2014, been misused to spread computer malware. The BBC reported in 2015 that "North Korean state media has suggested the disease was created by the U.S. military as a biological weapon."


Literature

Richard Preston's 1995 best-selling book, '' The Hot Zone'', dramatised the Ebola outbreak in Reston, Virginia. William Close's 1995 ''Ebola: A Documentary Novel of Its First Explosion'' and 2002 ''Ebola: Through the Eyes of the People'' focused on individuals' reactions to the 1976 Ebola outbreak in Zaire. Tom Clancy's 1996 novel, ''
Executive Orders ''Executive Orders'' is a techno-thriller novel, written by Tom Clancy and released on July 1, 1996. It picks up immediately where the final events of ''Debt of Honor'' (1994) left off, and features now-U.S. President Jack Ryan as he tries to d ...
'', involves a Middle Eastern terrorist attack on the United States using an airborne form of a deadly Ebola virus strain named "Ebola Mayinga" (see Mayinga N'Seka). As the Ebola virus epidemic in West Africa developed in 2014, a number of popular self-published and well-reviewed books containing sensational and misleading information about the disease appeared in electronic and printed formats. The authors of some such books admitted that they lacked medical credentials and were not technically qualified to give medical advice. The World Health Organization and the United Nations stated that such misinformation had contributed to the spread of the disease.


Other animals


Wild animals

Ebola has a high mortality rate among primates. Frequent outbreaks of Ebola may have resulted in the deaths of 5,000 gorillas. Outbreaks of Ebola may have been responsible for an 88% decline in tracking indices of observed chimpanzee populations in the 420 km2 Lossi Sanctuary between 2002 and 2003. Transmission among chimpanzees through meat consumption constitutes a significant risk factor, whereas contact between the animals, such as touching dead bodies and grooming, is not. Recovered gorilla carcasses have contained multiple Ebola virus strains, suggesting multiple introductions of the virus. Bodies decompose quickly and carcasses are not infectious after three to four days. Contact between gorilla groups is rare, suggesting that transmission among gorilla groups is unlikely, and that outbreaks result from transmission between viral reservoirs and animal populations.


Domestic animals

In 2012, it was demonstrated that the virus can travel without contact from pigs to nonhuman primates, although the same study failed to achieve transmission in that manner between primates. Dogs may become infected with EBOV but not develop symptoms. Dogs in some parts of Africa scavenge for food, and they sometimes eat EBOV-infected animals and also the corpses of humans. A 2005 survey of dogs during an EBOV outbreak found that although they remain asymptomatic, about 32 percent of dogs closest to an outbreak showed a seroprevalence for EBOV versus nine percent of those farther away. The authors concluded that there were "potential implications for preventing and controlling human outbreaks."


Reston virus

In late 1989, Hazelton Research Products' Reston Quarantine Unit in
Reston, Virginia Reston is a census-designated place in Fairfax County, Virginia and a principal city of the Washington metropolitan area. As of the 2020 U.S. Census, Reston's population was 63,226. Founded in 1964, Reston was influenced by the Garden City movem ...
, had an outbreak of fatal illness amongst certain lab monkeys. This lab outbreak was initially diagnosed as
simian haemorrhagic fever virus ''Deltaarterivirus hemfev'', formerly ''Simian hemorrhagic fever virus'' or ''simian haemorrhagic fever virus'' (SHFV), is a highly pathogenic virus in monkeys. It is a positive-stranded RNA virus classified in the family ''Arteriviridae''. It i ...
(SHFV) and occurred amongst a shipment of
crab-eating macaque The crab-eating macaque (''Macaca fascicularis''), also known as the long-tailed macaque and referred to as the cynomolgus monkey in laboratories, is a cercopithecine primate native to Southeast Asia. A species of macaque, the crab-eating macaqu ...
monkeys imported from the Philippines. Hazelton's veterinary pathologist in Reston sent tissue samples from dead animals to the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) at
Fort Detrick, Maryland Fort Detrick () is a United States Army Futures Command installation located in Frederick, Maryland. Historically, Fort Detrick was the center of the U.S. biological weapons program from 1943 to 1969. Since the discontinuation of that program, i ...
, where an ELISA test indicated the antibodies present in the tissue were a response to Ebola virus and not SHFV. An electron microscopist from USAMRIID discovered
filoviruses ''Filoviridae'' () is a family of single-stranded negative-sense RNA viruses in the order ''Mononegavirales''. Two members of the family that are commonly known are Ebola virus and Marburg virus. Both viruses, and some of their lesser known re ...
similar in appearance, in crystalloid aggregates and as single filaments with a shepherd's hook, to Ebola in the tissue samples sent from Hazelton Research Products' Reston Quarantine Unit. A US Army team headquartered at USAMRIID euthanised the surviving monkeys, and brought all the dead monkeys to Fort Detrick for study by the Army's veterinary pathologists and virologists, and eventual disposal under safe conditions. Blood samples were taken from 178 animal handlers during the incident. Of those, six animal handlers eventually seroconverted, including one who had cut himself with a bloody scalpel. Despite its status as a Level‑4 organism and its apparent pathogenicity in monkeys, when the handlers did not become ill, the CDC concluded that the virus had a very low pathogenicity to humans. The Philippines and the United States had no previous cases of Ebola infection, and upon further isolation, researchers concluded it was another strain of Ebola, or a new filovirus of Asian origin, which they named ''
Reston ebolavirus Reston virus (RESTV) is one of six known viruses within the genus ''Ebolavirus''. Reston virus causes Ebola virus disease in non-human primates; unlike the other five ebolaviruses, it is not known to cause disease in humans, but has caused asymp ...
'' (RESTV) after the location of the incident. Reston virus (RESTV) can be transmitted to pigs. Since the initial outbreak it has since been found in nonhuman primates in Pennsylvania, Texas, and Italy, where the virus had infected pigs. According to the WHO, routine cleaning and disinfection of pig (or monkey) farms with sodium hypochlorite or detergents should be effective in inactivating the ''Reston ebolavirus''. Pigs that have been infected with RESTV tend to show
symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an disease, illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormali ...
of the disease.


Research


Treatments

, no medication has been proven safe and effective for treating Ebola. By the time the Ebola virus epidemic in West Africa began in 2013, there were at least nine different candidate treatments. Several trials were conducted in late 2014, and early 2015, but some were abandoned due to lack of efficacy or lack of people to study. , two experimental treatments known as atoltivimab/maftivimab/odesivimab and
ansuvimab Ansuvimab, sold under the brand name Ebanga, is a monoclonal antibody medication for the treatment of ''Zaire ebolavirus'' (Ebolavirus) infection. The most common symptoms include fever, tachycardia (fast heart rate), diarrhea, vomiting, hypote ...
were found to be 90% effective.


Diagnostic tests

The diagnostic tests currently available require specialised equipment and highly trained personnel. Since there are few suitable testing centres in West Africa, this leads to delay in diagnosis. On 29 November 2014, a new 15-minute Ebola test was reported that if successful, "not only gives patients a better chance of survival, but it prevents transmission of the virus to other people." The new equipment, about the size of a laptop and solar-powered, allows testing to be done in remote areas. On 29 December 2014, the U.S. Food and Drug Administration (FDA) approved the LightMix Ebola Zaire rRT-PCR test for patients with symptoms of Ebola.


Disease models

Animal models and in particular non-human primates are being used to study different aspects of Ebola virus disease. Developments in
organ-on-a-chip An organ-on-a-chip (OOC) is a multi-channel 3-D microfluidic cell culture, integrated circuit (chip) that simulates the activities, mechanics and physiological response of an entire organ or an organ system, a type of artificial organ. It constitu ...
technology have led to a chip-based model for Ebola haemorrhagic syndrome.


See also

* Bibliography of Ebola


Notes


References

* ''The article uses public domain text from the CDC as cited.''


Bibliography

* * * * * * * *


External links


Ebola (Ebola Virus Disease)
nbsp;– Centers for Disease Control and Prevention, Viral Special Pathogens Branch.
Health topics: Ebola virus disease
nbsp;– World Health Organization.
Videos: Ebola outbreak response
nbsp;– World Health Organization. *
Ebola: What You Need to Know
nbsp;– '' Scientific American'' articles related to Ebola; note these are general reading articles, they are not scientific peer-reviewed research articles. {{Authority control Animal viral diseases Arthropod-borne viral fevers and viral haemorrhagic fevers Articles containing video clips Bat virome Biological weapons Health in Africa Hemorrhagic fevers Wikipedia medicine articles ready to translate Wikipedia infectious disease articles ready to translate Sexually transmitted diseases and infections Tropical diseases Virus-related cutaneous conditions West African Ebola virus epidemic Wikipedia pages referenced by the press Zoonoses so:Ebola virus disease