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In
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any
organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological me ...

organism
that can produce
disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting ...
. A pathogen may also be referred to as an infectious agent, or simply a germ. The term ''pathogen'' came into use in the 1880s. Typically, the term is used to describe an ''infectious''
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...
or agent, such as a
virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

virus
,
bacterium Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of all known organisms. Cells are the sma ...
,
protozoan Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of single-celled eukaryote Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus enclosed within a nuc ...
,
prion Prions are misfolded protein Protein folding is the physical process Physical changes are changes affecting the form of a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matte ...

prion
,
viroid Viroids are small single-stranded, circular RNA Circular RNA (or circRNA) is a type of single-stranded RNA which, unlike linear RNA, forms a covalently closed continuous loop. In circular RNA, the 3' and 5' ends normally present in an RNA molec ...
, or
fungus A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ve ...

fungus
. Small animals, such as certain worms or insects, can also cause or transmit disease. However, these animals are usually, in common parlance, referred to as
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is adaptation (biology), adapted structurally to this w ...
s rather than pathogens. The scientific study of microscopic organisms, including microscopic pathogenic organisms, is called
microbiology Microbiology (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appro ...

microbiology
, while
parasitology Parasitology is the study of parasites, their hosts, and the relationship between them. As a biological discipline, the scope of parasitology is not determined by the organism or environment in question but by their way of life. This means it f ...
refers to the scientific study of parasites and the organisms that host them. There are several pathways through which pathogens can invade a host. The principal pathways have different episodic time frames, but
soil Soil is a mixture In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, comp ...
has the longest or most persistent potential for harboring a pathogen. Diseases in humans that are caused by infectious agents are known as pathogenic diseases. Not all diseases are caused by pathogens, other causes are, for example,
toxin A toxin is a harmful substance produced within living cells or organisms; synthetic toxicants created by artificial processes are thus excluded. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived from the word toxic ...
s,
genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and li ...
s and the .


Pathogenicity

Pathogenicity is the potential disease-causing capacity of pathogens. Pathogenicity is related to
virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most contexts, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host (biology), host. The Pathogen#Pathogenicity, ...
in meaning, but some authorities have come to distinguish it as a ''qualitative'' term, whereas the latter is ''quantitative''. By this standard, an organism may be said to be pathogenic or non-pathogenic in a particular context, but not "more pathogenic" than another. Such comparisons are described instead in terms of relative virulence. Pathogenicity is also distinct from the transmissibility of a virus, which quantifies the risk of infection. A pathogen may be described in terms of its ability to produce
toxin A toxin is a harmful substance produced within living cells or organisms; synthetic toxicants created by artificial processes are thus excluded. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived from the word toxic ...
s, enter tissue, colonize, hijack nutrients, and its ability to immunosuppress the host.


Context-dependent pathogenicity

It is common to speak of an entire species of bacteria as pathogenic when it is identified as the cause of a disease ''(cf.
Koch's postulates 200px, Robert Hermann Koch (11 December 1843 – 27 May 1910) was a German physician who developed Koch's postulates. Koch's postulates ()
)''. However, the modern view is that pathogenicity depends on the microbial ecosystem as a whole. A bacterium may participate in
opportunistic infection An opportunistic infection is an infection An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the infectiou ...
s in
immunocompromised Immunodeficiency, also known as immunocompromisation, is a state in which the immune system The immune system is a network of biological processes that protects an organism In biology, an organism (from Ancient Greek, Greek: ὀργα ...
hosts, acquire
virulence factor Virulence factors (preferably known as pathogenicity factors or effectors in plant science) are cellular structures, molecules and regulatory systems that enable microbial pathogens (bacteria, viruses, fungi, and protozoa) to achieve the following ...
s by
plasmid A plasmid is a small, extrachromosomal DNA Extrachromosomal DNA (abbreviated ecDNA) is any DNA that is found off the chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryo ...
infection, become transferred to a different site within the host, or respond to changes in the overall numbers of other bacteria present. For example, infection of mesenteric
lymph glands A lymph node, or lymph gland, is a kidney-shaped Organ (anatomy), 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 lymphocy ...

lymph glands
of mice with ''
Yersinia ''Yersinia'' is a genus of bacteria in the family Yersiniaceae. ''Yersinia'' species are Gram-negative, coccobacilli bacteria, a few micrometers long and fractions of a micrometer in diameter, and are facultative anaerobes. Some members of ''Yers ...

Yersinia
'' can clear the way for continuing infection of these sites by ''
Lactobacillus ''Lactobacillus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...
'', possibly by a mechanism of "immunological scarring".


Related concepts


Virulence

Virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most contexts, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host (biology), host. The Pathogen#Pathogenicity, ...
(the tendency of a pathogen to reduce a host's fitness) evolves when a pathogen can spread from a diseased host, despite the host becoming debilitated.
Horizontal transmission Horizontal transmission is the transmission of organisms between biotic and/or abiotic members of an ecosystem that are not in a parent-progeny relationship. This concept has been generalized to include transmissions of infectious agents, symbiont ...
occurs between hosts of the same species, in contrast to
vertical transmission Vertical transmission of symbionts Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction In ecology Ecology (from el, οἶκος, "house ...
, which tends to evolve toward
symbiosis Symbiosis (from Ancient Greek, Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different Organism, biological organisms, be it Mutualism (biolog ...

symbiosis
(after a period of high morbidity and mortality in the population) by linking the pathogen's evolutionary success to the evolutionary success of the host organism.
Evolutionary biology Evolutionary biology is the subfield of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interacti ...
proposes that many pathogens evolve an optimal virulence at which the fitness gained by increased replication rates is balanced by trade-offs in reduced transmission, but the exact mechanisms underlying these relationships remain controversial.


Transmission

Transmission of pathogens occurs through many different routes, including airborne, direct or indirect contact, sexual contact, through blood, breast milk, or other body fluids, and through the fecal-oral route.


Types of pathogens


Algae

Algae are single-celled
eukaryote Eukaryotes () are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...

eukaryote
s that are generally non-pathogenic although pathogenic varieties do exist. ''
Protothecosis Protothecosis, otherwise known as Algaemia, is a disease found in dog The domestic dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated form of wolf. The dog descended from an ancient, extinct wolf, with the modern g ...
'' is a disease found in dogs, cats, cattle, and humans caused by a type of green alga known as
prototheca ''Prototheca'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to ...
that lacks chlorophyll. Often found in soil and sewage, the species '''' is the cause for most human cases of the rare infection of protothecosis.


Bacteria

The vast majority of bacteria, which can range between 0.15 and 700 μM in length, are harmless or beneficial to humans. However, a relatively small list of
pathogenic bacteria Pathogenic bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of a ...
can cause infectious diseases. Pathogenic bacteria have several ways that they can cause disease. They can either directly affect the cells of their host, produce endotoxins that damage the cells of their host, or cause a strong enough immune response that the host cells are damaged. One of the bacterial diseases with the highest
disease burden Disease burden is the impact of a health problem as measured by financial cost, mortality, morbidity A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part o ...

disease burden
is
tuberculosis Tuberculosis (TB) is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the in ...

tuberculosis
, caused by the bacterium ''
Mycobacterium tuberculosis ''Mycobacterium tuberculosis'' (M. tb) is a species of pathogenic bacteria Pathogenic bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', mea ...

Mycobacterium tuberculosis
'', which killed 1.5 million people in 2013, mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally significant diseases, such as
pneumonia Pneumonia is an inflammatory Inflammatory may refer to: * Inflammation, a biological response to harmful stimuli * The word ''inflammatory'' is also used to refer literally to fire and flammability, and figuratively in relation to comments t ...

pneumonia
, which can be caused by bacteria such as ''
Streptococcus ''Streptococcus'' is a genus of gram-positive bacteria, gram-positive ' (plural ) or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Firmicutes. Cell divisio ...

Streptococcus
'' and ''
Pseudomonas ''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 validly described species. The members of the genus demonstrate a great deal of Metabolism, metabolic diversity and conse ...

Pseudomonas
'', and
foodborne illness Foodborne illness (also foodborne disease and colloquially referred to as food poisoning) is any Disease, illness resulting from the spoilage of food contaminant, contaminated food by pathogenic bacteria, viruses, or parasites that contaminate fo ...
es, which can be caused by bacteria such as ''
Shigella ''Shigella'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to ...
'', ''
Campylobacter ''Campylobacter'' (meaning "curved bacteria") is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classificat ...

Campylobacter
'', and ''
Salmonella ''Salmonella'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circ ...
''. In patients with
cystic fibrosis Cystic fibrosis (CF) is a genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene In biology, a gene (from ''genos'' "...Wilhelm Johan ...
, ''Pseudomonas'' bacteria can form a biofilm that has a high resistance to the immune system and antibiotics by developing adaptive mutations and producing virulence factors. Pathogenic bacteria also cause infections such as
tetanus Tetanus, also known as lockjaw, is a bacterial infection Pathogenic bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), do ...
,
typhoid fever Typhoid fever, also known as typhoid, is a disease caused by ''Salmonella ''Salmonella'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living an ...
,
diphtheria Diphtheria is an infection caused by the bacteria, bacterium ''Corynebacterium diphtheriae''. Most infections are asymptomatic or have a mild Course (medicine), clinical course, but in some outbreaks more than 10% of those diagnosed with the di ...

diphtheria
,
syphilis Syphilis is a sexually transmitted infection Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs) and the older term venereal disease, are infection An infection is the invasion of an orga ...
, and
leprosy Leprosy, also known as Hansen's disease (HD), is a long-term Long-Term Capital Management L.P. (LTCM) was a hedge fund''A financial History of the United States Volume II: 1970–2001'', Jerry W. Markham, Chapter 5: "Bank Consolidation", M. E. ...

leprosy
.


Fungi

Fungi are eukaryotic organisms that can function as pathogens. There are approximately 300 known fungi that are pathogenic to humans including ''
Candida albicans ''Candida albicans'' is an opportunistic pathogenic yeast Yeasts are eukaryotic Eukaryotes () are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous s ...

Candida albicans
'', which is the most common cause of
thrush ''The Man from U.N.C.L.E.'' is an American spy fiction Spy fiction, a genre of literature involving espionage Espionage or spying is the act of obtaining Secrecy, secret or Confidentiality, confidential information or divulging of the sa ...

thrush
, and ''
Cryptococcus neoformans ''Cryptococcus neoformans'' is an encapsulated yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species ...

Cryptococcus neoformans
'', which can cause a severe form of
meningitis Meningitis is an acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology#acute, glossary of leaf morphology * Acute (medicine), a disease that it is of short dur ...
. The typical fungal spore size is <4.7 μm in length, but some spores may be larger.


Prions

Prions Prions are misfolded protein Protein folding is the physical process Physical changes are changes affecting the form of a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matte ...
are misfolded proteins that are transmissible and can influence abnormal folding of normal proteins in the brain. They do not contain any DNA or RNA and cannot replicate other than to convert already existing normal proteins to the misfolded state. These abnormally folded proteins are found characteristically in many neurodegenerative diseases as they aggregate the central nervous system and create plaques that damages the tissue structure. This essentially creates "holes" in the tissue. It has been found that prions transmit three ways: obtained, familial, and sporadic. It has also been found that plants play the role of vector for prions. There are eight different diseases that affect mammals that are caused by prions such as
scrapie Scrapie () is a fatal, degenerative disease affecting the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies (TSEs), and as such it is thought to be caused by a prion. Scrapie has been known since ...
,
bovine spongiform encephalopathy Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is a neurodegenerative disease A neurodegenerative disease is caused by the progressive loss of structure or function of neuron A neuron or nerve cell is an membr ...
(mad cow disease) and feline spongiform encephalopathy (FSE). There are also ten diseases that affect humans, such as
Creutzfeldt–Jakob disease Creutzfeldt–Jakob disease (CJD), also known as subacute spongiform encephalopathy or neurocognitive disorder due to prion disease, is a fatal neurodegeneration, degenerative brain disorder. Early symptoms include memory problems, behavioral ch ...
(CJD). and
Fatal familial insomnia Fatal insomnia is an extremely rare genetic (and rarely sporadic) disorder that results in trouble sleeping Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling as ...
(FFI).


Viroids

Not to be confused with virusoid or
virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

virus
. Viroids are the smallest infectious pathogens known. They are composed solely of a short strand of circular, single-stranded RNA that has no protein coating. All known viroids are inhabitants of higher plants, and most cause diseases, whose respective economic importance on humans vary widely.


Viruses

Viruses are small particles, typically between 20 and 300 nanometers in length, containing RNA or DNA. Viruses require a host cell to replicate. Some of the diseases that are caused by viral pathogens include
smallpox Smallpox was an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to the infectious ...

smallpox
,
influenza Influenza, commonly known as "the flu", is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), ...

influenza
,
mumps Mumps is a viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characteris ...

mumps
,
measles Measles is a highly contagious infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to ...
,
chickenpox Chickenpox, also known as varicella, is a highly contagious Contagious may refer to: * Contagious disease Literature * Contagious (magazine), a marketing publication * Contagious (novel), ''Contagious'' (novel), a science fiction thriller ...

chickenpox
,
ebola 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 illness A disease is a particular abnormal c ...
,
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus ''Lentivirus'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, inc ...

HIV
,
rubella Rubella, also known as German measles or three-day measles, is an infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An inf ...

rubella
, and
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease A contagious disease is a disease A disease is a particular abnormal condition that negatively affects the structure A structure is an arrangement and organization o ...

COVID-19
. Pathogenic viruses are mainly from the families
Adenoviridae Adenoviruses (members of the family ''Adenoviridae'') are medium-sized (90–100 nm), nonenveloped (without an outer lipid bilayer) virus A virus is a submicroscopic infectious agent that Viral replication, replicates only inside the ...

Adenoviridae
,
Coronaviridae ''Coronaviridae'' is a family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain the well-being of its members and of soc ...
,
Picornaviridae Picornaviruses are a group of related Viral envelope, nonenveloped RNA viruses which infect vertebrates including fish, mammals, and birds. They are viruses that represent a large family of small, Positive-sense single-stranded RNA virus, positiv ...
,
Herpesviridae ''Herpesviridae'' is a large family (biology), family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek wor ...
,
Hepadnaviridae ''Hepadnaviridae'' is a family of viruses. Humans, apes, and birds serve as natural hosts. There are currently 18 species in this family, divided among 5 genera. Its best-known member is hepatitis B virus. Diseases associated with this family ...
,
Flaviviridae ''Flaviviridae'' is a family of enveloped positive-strand RNA viruses which mainly infect mammals and birds. They are primarily spread through arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a S ...
,
Retroviridae A retrovirus is a type of virus A virus is a submicroscopic infectious agent that Viral replication, replicates only inside the living Cell (biology), cells of an organism. Viruses infect all types of life forms, from animals and plant ...
,
Orthomyxoviridae ''Orthomyxoviridae'' (ὀρθός, ''orthós'', Greek for "straight"; μύξα, ''mýxa'', Greek for "mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mu ...
,
Paramyxoviridae ''Paramyxoviridae'' (from Ancient Greek, Greek ''para-'' “by the side of” and ''myxa'' “mucus”) is a family of negative-strand RNA viruses in the order ''Mononegavirales''. Vertebrates serve as natural hosts. Diseases associated with this f ...
, Papovaviridae,
Polyomavirus ''Polyomaviridae'' is a family of viruses A virus is a wikt:submicroscopic, submicroscopic infectious agent that Viral replication, replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, fr ...

Polyomavirus
,
Rhabdoviridae ''Rhabdoviridae'' is a family of Negative-strand RNA virus, negative-strand RNA viruses in the order ''Mononegavirales''. Vertebrate, Vertebrates (including Mammal, mammals and humans), Invertebrate, invertebrates, Plant, plants, fungi and proto ...

Rhabdoviridae
, and
TogaviridaeThis category is for articles about virus families (or redirects to such articles). There should be no subcategories. families Families (biology) ...
. HIV is a notable member of the family Retroviridae which affected 37.9 million people across the world in 2018.


Other parasites

Protozoans are single-celled eukaryotes that feed on microorganisms and organic tissues. Considered as "one-celled animal" as they have animal like behaviors such as motility, predation, and a lack of a cell wall. Many protozoan pathogens are considered human parasites as they cause a variety of diseases such as:
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign fo ...

malaria
,
amoebiasis Amoebiasis or amoebic dysentery Dysentery () is a type of gastroenteritis Gastroenteritis, also known as infectious diarrhea and gastro, is inflammation of the gastrointestinal tract The gastrointestinal tract, (GI tract, GIT, digest ...
,
giardiasis Giardiasis is a parasitic disease caused by ''Giardia duodenalis'' (also known as ''G. lamblia'' and ''G. intestinalis''). About 10% of those infected have no symptoms. Individuals who experience symptoms may have diarrhea, abdominal pain ...
,
toxoplasmosis Toxoplasmosis is a parasitic disease caused by ''Toxoplasma gondii'', an apicomplexan. Infections with toxoplasmosis usually cause no obvious symptoms in adults. Occasionally, people may have a few weeks or months of mild, flu-like illness such as ...
,
cryptosporidiosis Cryptosporidiosis, sometimes informally called crypto, is a parasitic disease A parasitic disease, also known as parasitosis, is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, ...
,
trichomoniasis Trichomoniasis (trich) is an infectious disease caused by the parasite '' Trichomonas vaginalis''. About 70% of women and men do not have symptoms when infected. When symptoms do occur they typically begin 5 to 28 days after exposure. Symptoms ca ...
,
Chagas disease Chagas disease, also known as American trypanosomiasis, is a tropical disease, tropical parasitic disease caused by ''Trypanosoma cruzi''. It is spread mostly by insects known as ''Triatominae'', or "kissing bugs". The symptoms change over the ...
,
leishmaniasis Leishmaniasis is a wide array of clinical manifestations caused by parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, ...
, African trypanosomiasis (sleeping sickness), ''Acanthamoeba'' keratitis, and
primary amoebic meningoencephalitis Naegleriasis (also known as primary amoebic meningoencephalitis; PAM) is an almost invariably fatal infection of the brain by the free-living unicellular A unicellular organism, also known as a single-celled organism, is an organism that consi ...
(naegleriasis).
Parasitic worm Parasitic worms, also known as helminths, are large macroparasites; adults can generally be seen with the naked eye. Many are intestinal worms An intestinal parasite infection is a condition in which a parasite Parasitism is a symbi ...
s (helminths) are macroparasites that can be seen by the naked eye. Worms live and feed in their living host, receiving nourishment and shelter while affecting the host's way of digesting nutrients. They also manipulate the host's immune system by secreting immunomodulatory products which allows them to live in their host for years. Many parasitic worms are more commonly intestinal that are soil-transmitted and infect the digestive tract; other parasitic worms are found in the host's blood vessels. Parasitic worms living in the host can cause weakness and even lead to many diseases. Parasitic worms can cause many diseases to both humans and animals.
Helminthiasis Helminthiasis, also known as worm infection, is any macroparasitic disease of humans and other animals in which a part of the body is infected with parasitic Parasitism is a Symbiosis, symbiotic biological interactions, relationship betwe ...
(worm infection),
ascariasis Ascariasis is a disease caused by the parasitic roundworm ''Ascaris lumbricoides''. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may in ...
, and
enterobiasis Pinworm infection, also known as enterobiasis, is a human parasitic disease caused by the pinworm Pinworm infection, also known as enterobiasis, is a human parasitic disease caused by the pinworm (parasite), pinworm. The most common symptom i ...
(pinworm infection) are a few that are caused by various parasitic worms.


Pathogen hosts


Bacteria

Although bacteria can be pathogens themselves, they can also be infected by pathogens.
Bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, ...

Bacteriophage
s are viruses, also known as phage (plural) and phages, that infect bacteria often leading to the death of the bacteria that was infected. Common bacteriophages include T7 and
Lambda Lambda (; uppercase , lowercase ; el, λάμ(β)δα, ''lám(b)da'') is the 11th letter of the Greek alphabet, representing the sound Dental, alveolar and postalveolar lateral approximants, /l/. In the system of Greek numerals, lambda has a ...

Lambda
phage. There are bacteriophages that infect every kind of bacteria including both
gram-negative Gram-negative bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few microm ...
and
gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacte ...
. Even
pathogenic bacteria Pathogenic bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of a ...
that infect other species, including humans, can be infected with a phage.


Plants

Plants can play host to a wide range of pathogen types including viruses, bacteria, fungi, nematodes, and even other plants. Notable plant viruses include the
Papaya ringspot virus ''Papaya ringspot virus'' (PRSV) is a pathogen In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular in ...
which has caused millions of dollars of damage to farmers in Hawaii and Southeast Asia, and the
Tobacco mosaic virus ''Tobacco mosaic virus'' (TMV) is a positive-sense single-stranded RNA virus Positive-strand RNA viruses (+ssRNA viruses) are a group of related viruses that have positive-sense, single-stranded genomes made of ribonucleic acid. The positiv ...

Tobacco mosaic virus
which caused scientist
Martinus Beijerinck Martinus Willem Beijerinck (, 16 March 1851 – 1 January 1931) was a Dutch microbiologist A microbiologist (from Greek ) is a scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge i ...

Martinus Beijerinck
to coin the term "virus" in 1898. Bacterial plant pathogens are also a serious problem causing leaf spots, blights, and rots in many plant species. The top two bacterial pathogens for plants are ''
Pseudomonas syringae ''Pseudomonas syringae'' is a rod-shaped, Gram-negative Gram-negative bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), ...
'' and ''
Ralstonia solanacearum ''Ralstonia solanacearum'' is an aerobic non-spore-forming, Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bacterial differentiation. They are charac ...
'' which cause leaf browning and other issues in potatoes, tomatoes, and bananas.
Fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

Fungi
are another major pathogen type for plants. They can cause a wide variety of issues such as shorter plant height, growths or pits on tree trunks, root or seed rot, and leaf spots. Common and serious plant fungi include the ,
Dutch elm disease Dutch elm disease (DED) is caused by a member of the sac fungi Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It ...

Dutch elm disease
,
chestnut blight The pathogen In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiolog ...

chestnut blight
and the and diseases of cherries, plums, and peaches. It is estimated that pathogenic fungi alone cause up to a 65% reduction in crop yield. Overall, plants have a wide array of pathogens and it has been estimated that only 3% of the disease caused by plant pathogens can be managed.


Animals

Animals often get infected with many of the same or similar pathogens as humans including prions, viruses, bacteria, and fungi. While wild animals often get illnesses, the larger danger is for livestock animals. It is estimated that in rural settings, 90% or more of livestock deaths can be attributed to pathogens. The prion disease
bovine spongiform encephalopathy Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is a neurodegenerative disease A neurodegenerative disease is caused by the progressive loss of structure or function of neuron A neuron or nerve cell is an membr ...
, commonly known as Mad cow disease, is one of the few prion diseases that affect animals. Other animal diseases include a variety of immunodeficiency disorders that are caused by viruses related to the Human immunodeficiency virus (HIV) including BIV and FIV.


Humans

Humans can be infected with many types of pathogens including prions, viruses, bacteria, and fungi. Viruses and bacteria that infect humans can cause symptoms such as sneezing, coughing, fever, vomiting, and even lead to death. Some of these symptoms are caused by the virus itself, while others are caused by the immune system of the infected person.


Treatment


Prion

Despite many attempts, to date no therapy has been shown to halt the progression of prion diseases.


Virus

A variety of prevention and treatment options exist for some viral pathogens.
Vaccine A vaccine is a biological preparation that provides active acquired immunity The adaptive immune system, also referred as the acquired immune system, is a subsystem of the immune system The immune system is a network of biological process ...

Vaccine
s are one common and effective preventive measure against a variety of viral pathogens. Vaccines prime the immune system of the host, so that when the potential host encounters the virus in the wild, the immune system can defend against infection quickly. Vaccines exist for viruses such as the
measles Measles is a highly contagious infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), host tissues to ...
,
mumps Mumps is a viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infection, infectious virus particles (virions) attach to and enter susceptible cells. Structural characteris ...

mumps
, and
rubella Rubella, also known as German measles or three-day measles, is an infection An infection is the invasion of an organism's body by , their multiplication, and the reaction of tissues to the infectious agents and the s they produce. An inf ...

rubella
viruses and the
influenza Influenza, commonly known as "the flu", is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and the reaction of host (biology), ...

influenza
virus. Some viruses such as
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus ''Lentivirus'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, inc ...

HIV
,
dengue 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 Fever, also referred to as pyrexia, is defined as having a tem ...
, and
chikungunya Chikungunya is an infection caused by the ''Chikungunya virus'' (CHIKV). Symptoms include fever and arthralgia, joint pains. These typically occur two to twelve days after exposure. Other symptoms may include headache, muscle pain, joint swelling ...
do not have vaccines available. Treatment of viral infections often involves treating the symptoms of the infection rather than providing any medication that affects the viral pathogen itself. Treating the symptoms of a viral infection gives the host immune system time to develop antibodies against the viral pathogen which will then clear the infection. In some cases, treatment against the virus is necessary. One example of this is HIV where
antiretroviral therapy The management of HIV/AIDS normally includes the use of multiple antiretroviral drugs The management of HIV/AIDS normally includes the use of multiple antiretroviral drugs in an attempt to control HIV infection. There are several classes of antir ...
, also known as ART or HAART, is needed to prevent immune cell loss and the progression into AIDS.


Bacteria

Much like viral pathogens, infection by certain bacterial pathogens can be prevented via vaccines. Vaccines against bacterial pathogens include the
anthrax vaccine Vaccines against the livestock and human disease anthrax—caused by the bacterium ''Bacillus anthracis''—have had a prominent place in the history of medicine, from Pasteur’s pioneering 19th-century work with cattle (the first effective bacter ...
and the
pneumococcal vaccine Pneumococcal vaccines are vaccine A vaccine is a biological preparation that provides active acquired immunity The adaptive immune system, also referred as the acquired immune system, is a subsystem of the immune system The immune syste ...
. Many other bacterial pathogens lack vaccines as a preventive measure, but infection by these bacteria can often be treated or prevented with
antibiotic An antibiotic is a type of antimicrobial An antimicrobial is an agent that kills microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system t ...
s. Common antibiotics include
amoxicillin Amoxicillin is an antibiotic An antibiotic is a type of antimicrobial An antimicrobial is an agent that kills microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is ...

amoxicillin
,
ciprofloxacin Ciprofloxacin is an antibiotic used to treat a number of bacterial infections. This includes bone and joint infections, intra abdominal infections, certain type of infectious diarrhea, respiratory tract infections, skin infections, typhoid f ...
, and
doxycycline Doxycycline is a broad-spectrum tetracycline-class antibiotic used in the treatment of infections caused by bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a ...

doxycycline
. Each antibiotic has different bacteria that it is effective against and has different mechanisms to kill that bacteria. For example,
doxycycline Doxycycline is a broad-spectrum tetracycline-class antibiotic used in the treatment of infections caused by bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a ...

doxycycline
inhibits the synthesis of new proteins in both
gram-negative Gram-negative bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few microm ...
and
gram-positive bacteria In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacte ...
which leads to the death of the affected bacteria. Due in part to over-prescribing antibiotics in circumstances where they are not needed, some bacterial pathogens have developed antibiotic resistance and are becoming hard to treat with classical antibiotics. A genetically distinct strain of
Staphylococcus aureus ''Staphylococcus aureus'' is a Gram-positive bacteria, Gram-positive coccus, round-shaped bacterium, a member of the Firmicutes, and is a usual member of the microbiota of the body, frequently found in the Respiratory tract, upper respiratory ...
called
MRSA Methicillin-resistant ''Staphylococcus aureus'' (MRSA) refers to a group of Gram-positive bacteria that are genetically distinct from other strain (biology), strains of ''Staphylococcus aureus''. MRSA is responsible for several difficult-to-trea ...
is one example of a bacterial pathogen that is difficult to treat with common antibiotics. A report released in 2013 by the Center for Disease Control (CDC) estimated that each year in the United States, at least 2 million people get an antibiotic-resistant bacterial infection, and at least 23,000 people die from those infections. Due to their indispensability in Bacteria, essential persistent DNA methyltransferases are potential targets for the development of epigenetic inhibitors capable of, for example, enhance the therapeutic activity of antimicrobials, or decrease a pathogen's virulence.


Fungi

Infection by fungal pathogens is treated with anti-fungal medication. Fungal infections such as
athlete's foot Athlete's foot, known medically as ''tinea pedis'', is a common skin infection A skin infection is an infection An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multipl ...

athlete's foot
,
jock itch Jock may refer to: Common meanings * Jock (stereotype), a North American term for a stereotypical male athlete * Jock, a derogatory term for Scottish people mostly used by the English * Short for jockstrap, an item of male protective undergarmen ...

jock itch
, and
ringworm Dermatophytosis, also known as ringworm, is a fungal infection Mycosis is an infectious disease An infection is the invasion of an organism's body Tissue (biology), tissues by Pathogen, disease-causing agents, their multiplication, and t ...

ringworm
are infections of the skin and can be treated with topical anti-fungal medications like
Clotrimazole Clotrimazole, sold under the brand name Lotrimin, among others, is an antifungal medication. It is used to treat vaginal yeast infections, oral thrush, diaper rash, pityriasis versicolor, and types of ringworm including athlete's foot and jock i ...

Clotrimazole
. Other common fungal infections include infections by the yeast strain
Candida albicans ''Candida albicans'' is an opportunistic pathogenic yeast Yeasts are eukaryotic Eukaryotes () are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous s ...

Candida albicans
. Candida can cause infections of the mouth or throat, commonly referred to as
thrush ''The Man from U.N.C.L.E.'' is an American spy fiction Spy fiction, a genre of literature involving espionage Espionage or spying is the act of obtaining Secrecy, secret or Confidentiality, confidential information or divulging of the sa ...

thrush
, or it can cause vaginal infections. These internal infections can either be treated with anti-fungal creams or with oral medication. Common anti-fungal drugs for internal infections include the
Echinocandin Echinocandins are a class of antifungal drug An antifungal medication, also known as an antimycotic medication, is a pharmaceutical A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug ...
family of drugs and
Fluconazole Fluconazole is an antifungal medication An antifungal medication, also known as an antimycotic medication, is a pharmaceutical A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug ...

Fluconazole
.


Algae

Algae are commonly not thought of as pathogens, but the genus ''Prototheca'' is known to cause disease in humans''.'' Treatment for this kind of infection is currently under investigation and there is no consistency in clinical treatment.


Sexual interactions

Many pathogens are capable of sexual interaction. Among
pathogenic bacteria Pathogenic bacteria are bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of biological cell The cell (from Latin ''cella'', meaning "small room") is the basic structural, functional, and biological unit of a ...
, sexual interaction occurs between cells of the same species by the process of natural genetic transformation. Transformation involves the transfer of
DNA Deoxyribonucleic acid (; DNA) is a molecule A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically Electricity is the set of physical ...

DNA
from a donor cell to a recipient cell and the integration of the donor DNA into the recipient
genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, M ...

genome
by recombination. Examples of bacterial pathogens capable of natural transformation are ''
Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophile, microaerophilic, spiral bacteria, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, ...

Helicobacter pylori
'', ''
Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, Coccobacillus, coccobacillary, facultative anaerobic organism, facultatively anaerobic Capnophile, capnophilic pathogenic bacteriu ...

Haemophilus influenzae
'', ''
Legionella pneumophila ''Legionella pneumophila'' is a thin, aerobic, pleomorphic, flagellated, non-spore-forming, Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram stain, gram-staining method of bacteri ...
'', ''
Neisseria gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. It causes the sexually transmit ...

Neisseria gonorrhoeae
'' and ''
Streptococcus pneumoniae ''Streptococcus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology Biology is the natural science that studies life and living organisms, including ...

Streptococcus pneumoniae
''.
Eukaryotic Eukaryotes () are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...

Eukaryotic
pathogens are often capable of sexual interaction by a process involving
meiosis Meiosis (; , because it is a reductional division) is a special type of of in organisms used to produce the , such as or . It involves two rounds of division that ultimately result in four cells with only one copy of each (). Additionall ...

meiosis
and
syngamy Fertilisation or fertilization (see spelling differences Despite the various English dialects Dialect The term dialect (from Latin , , from the Ancient Greek word , , "discourse", from , , "through" and , , "I speak") is used in ...
. Meiosis involves the intimate pairing of homologous chromosomes and recombination between them. Examples of eukaryotic pathogens capable of sex include the protozoan parasites ''
Plasmodium falciparum ''Plasmodium falciparum'' is a unicellular A unicellular organism, also known as a single-celled organism, is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All org ...

Plasmodium falciparum
'', ''
Toxoplasma gondii ''Toxoplasma gondii'' () is an obligate intracellular parasitic protozoan Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of single-celled eukaryote Eukaryotes () are organisms ...

Toxoplasma gondii
'', ''
Trypanosoma brucei ''Trypanosoma brucei'' is a species of parasitic kinetoplastid Kinetoplastida (or Kinetoplastea, as a class) is a group of flagellated A flagellum (; plural: flagella) is a lash-like appendage that protrudes from the soma (biology), cell ...

Trypanosoma brucei
'', ''
Giardia intestinalis ''Giardia duodenalis'', also known as ''Giardia intestinalis'' and ''Giardia lamblia'', is a flagellate 's '' Artforms of Nature'', 1904 (''Giardia lamblia'') ('' Chlamydomonas'') A flagellate is a cell or organism with one or more whip-like ...

Giardia intestinalis
'', and the fungi ''
Aspergillus fumigatus ''Aspergillus fumigatus'' is a species of fungus A fungus (plural: fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more fam ...

Aspergillus fumigatus
'', ''
Candida albicans ''Candida albicans'' is an opportunistic pathogenic yeast Yeasts are eukaryotic Eukaryotes () are organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous s ...

Candida albicans
'' and ''
Cryptococcus neoformans ''Cryptococcus neoformans'' is an encapsulated yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species ...

Cryptococcus neoformans
''.
Virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

Virus
es may also undergo sexual interaction when two or more viral
genome In the fields of molecular biology Molecular biology is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, M ...

genome
s enter the same host cell. This process involves pairing of homologous genomes and recombination between them by a process referred to as multiplicity reactivation. Examples of viruses that undergo this process are
herpes simplex virus Herpes simplex virus 1 and 2 (HSV-1 and HSV-2), also known by their taxonomical names ''Human alphaherpesvirus 1'' and ''Human alphaherpesvirus 2'', are two members of the Herpesviridae#Human herpesvirus types, human ''Herpesviridae'' family, a ...
,
human immunodeficiency virus The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause AIDS, acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the ...

human immunodeficiency virus
, and
vaccinia ''Vaccinia virus'' (VACV or VV) is a large, complex, enveloped virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physi ...
virus. The sexual processes in bacteria, microbial eukaryotes, and viruses all involve recombination between homologous genomes that appears to facilitate the
repair The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery, building infrastructure, and supporting utilities in industrial, business, and residential installati ...

repair
of genomic damage to the pathogens caused by the defenses of their respective target hosts.


See also

* Antigenic escape * Ecological competence *
Emerging Pathogens Institute The Emerging Pathogens Institute is an interdisciplinary research institution associated with the University of Florida The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research univer ...

Emerging Pathogens Institute
*
Human pathogenA human pathogen is a pathogen In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiol ...
* Pathogen-Host Interaction Database (PHI-base)


References


External links


Pronunciation Guide to Microorganisms (1)

Pronunciation Guide to Microorganisms (2)
{{Authority control Infectious diseases Microbiology