Pyrexia
   HOME

TheInfoList



OR:

Fever, also referred to as pyrexia, is defined as having a
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using values between in humans. The increase in set point triggers increased
muscle contraction Muscle contraction is the activation of tension-generating sites within muscle cells. In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as ...
s and causes a feeling of
cold Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjective perception. A lower bound to temperature is absolute zero, defined as 0.00K on the Kelvin scale, an absolute thermodynamic ...
or
chills Chills is a feeling of coldness occurring during a high fever, but sometimes is also a common symptom which occurs alone in specific people. It occurs during fever due to the release of cytokines and prostaglandins as part of the inflammatory r ...
. This results in greater heat production and efforts to conserve heat. When the set point temperature returns to normal, a person feels hot, becomes flushed, and may begin to
sweat Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distribut ...
. Rarely a fever may trigger a
febrile seizure A febrile seizure, also known as a fever fit or febrile convulsion, is a seizure associated with an increased body temperature but without any intracranial infection. Febrile seizures affect 2–7% of children and are more common in boys than gi ...
, with this being more common in young children. Fevers do not typically go higher than . A fever can be caused by many
medical conditions A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medica ...
ranging from non-serious to
life-threatening Lethality (also called deadliness or perniciousness) is how capable something is of causing death. Most often it is used when referring to diseases, chemical weapons, biological weapons, or their toxic chemical components. The use of this te ...
. This includes viral,
bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
, and
parasitic infections 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, adapted structurally to this way of lif ...
—such as
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 ...
, the
common cold The common cold or the cold is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx. Signs and symptoms may appear fewer than two days after exposu ...
,
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 ...
,
urinary tract infections A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...
,
appendicitis Appendicitis is inflammation of the appendix. Symptoms commonly include right lower abdominal pain, nausea, vomiting, and decreased appetite. However, approximately 40% of people do not have these typical symptoms. Severe complications of a rup ...
, Lassa,
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
, and
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
. Non-infectious causes include
vasculitis Vasculitis is a group of disorders that destroy blood vessels by inflammation. Both arteries and veins are affected. Lymphangitis (inflammation of lymphatic vessels) is sometimes considered a type of vasculitis. Vasculitis is primarily caused b ...
,
deep vein thrombosis Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enla ...
,
connective tissue disease A connective tissue disease (collagenosis) is any disease that has the connective tissues of the body as a target of pathology. Connective tissue is any type of biological tissue with an extensive extracellular matrix that supports, binds togeth ...
, side effects of medication or vaccination, and
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
. It differs from
hyperthermia Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...
, in that hyperthermia is an increase in body temperature over the temperature set point, due to either too much heat production or not enough
heat loss Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...
. Treatment to reduce fever is generally not required. Treatment of associated pain and inflammation, however, may be useful and help a person rest. Medications such as
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 ...
or
paracetamol Paracetamol, also known as acetaminophen, is a medication used to treat fever and mild to moderate pain. Common brand names include Tylenol and Panadol. At a standard dose, paracetamol only slightly decreases body temperature; it is inferior ...
(acetaminophen) may help with this as well as lower temperature. Children younger than three months require medical attention, as might people with serious medical problems such as a
compromised immune system Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...
or people with other symptoms.
Hyperthermia Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...
requires treatment. Fever is one of the most common
medical signs Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...
. It is part of about 30% of healthcare visits by children and occurs in up to 75% of adults who are seriously sick. While fever evolved as a defense mechanism, treating a fever does not appear to improve or worsen outcomes. Abstract alone is in German and in English. Fever is often viewed with greater concern by parents and healthcare professionals than is usually deserved, a phenomenon known as fever phobia.


Associated symptoms

A fever is usually accompanied by
sickness behavior 350px, Ancher, Michael, "The Sick Girl", 1882, Statens Museum for Kunst Sickness behavior is a coordinated set of adaptive behavioral changes that develop in ill individuals during the course of an infection. They usually, but not always, accom ...
, which consists of
lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...
, depression,
loss of appetite Anorexia is a medical term for a loss of appetite. While the term in non-scientific publications is often used interchangeably with anorexia nervosa, many possible causes exist for a loss of appetite, some of which may be harmless, while others i ...
,
sleepiness Somnolence (alternatively sleepiness or drowsiness) is a state of strong desire for sleep, or sleeping for unusually long periods (compare hypersomnia). It has distinct meanings and causes. It can refer to the usual state preceding falling asleep ...
,
hyperalgesia Hyperalgesia ( or ; 'hyper' from Greek ὑπέρ (huper, “over”), '-algesia' from Greek algos, ἄλγος (pain)) is an abnormally increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves and can ...
, dehydration, and the inability to concentrate. Sleeping with a fever can often cause intense or confusing nightmares, commonly called "fever dreams". Mild to severe
delirium Delirium (also known as acute confusional state) is an organically caused decline from a previous baseline of mental function that develops over a short period of time, typically hours to days. Delirium is a syndrome encompassing disturbances in ...
(which can also cause
hallucinations A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinatio ...
) may also present itself during high fevers.


Diagnosis

A range for normal temperatures has been found. Central temperatures, such as rectal temperatures, are more accurate than peripheral temperatures. Fever is generally agreed to be present if the elevated temperature is caused by a raised set point and: * Temperature in the
anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, d ...
(rectum/rectal) is at or over An
ear An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...
(tympanic) or
forehead In human anatomy, the forehead is an area of the head bounded by three features, two of the skull and one of the scalp. The top of the forehead is marked by the hairline, the edge of the area where hair on the scalp grows. The bottom of the fore ...
(temporal) temperature may also be used. * Temperature in the mouth (oral) is at or over in the morning or over in the afternoon * Temperature under the arm (axillary) is usually about below core body temperature. In adults, the normal range of oral temperatures in healthy individuals is among men and among women, while when taken rectally it is among men and among women, and for
ear An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...
measurement it is among men and among women. Normal body temperatures vary depending on many factors, including age, sex, time of day, ambient temperature, activity level, and more. Normal daily temperature variation has been described as 0.5 °C (0.9 °F). A raised temperature is not always a fever. For example, the temperature rises in healthy people when they exercise, but this is not considered a fever, as the set point is normal. On the other hand, a "normal" temperature may be a fever, if it is unusually high for that person; for example,
medically frail Frailty is a common geriatric syndrome that embodies an elevated risk of catastrophic declines in health and function among older adults. Frailty is a condition associated with ageing, and it has been recognized for centuries. It is also a marke ...
elderly people have a decreased ability to generate body heat, so a "normal" temperature of may represent a clinically significant fever.


Hyperthermia

Hyperthermia Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...
is an elevation of body temperature over the temperature set point, due to either too much heat production or not enough
heat loss Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...
. Hyperthermia is thus not considered fever. Hyperthermia is not to be confused with
hyperpyrexia Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
(which is a very high fever). Clinically, it is important to distinguish between fever and hyperthermia as hyperthermia may quickly lead to death and does not respond to antipyretic medications. The distinction may however be difficult to make in an emergency setting, and is often established by identifying possible causes.


Types

Various patterns of measured patient temperatures have been observed, some of which may be indicative of a particular
medical diagnosis Medical diagnosis (abbreviated Dx, Dx, or Ds) is the process of determining which disease or condition explains a person's symptoms and signs. It is most often referred to as diagnosis with the medical context being implicit. The information re ...
: *
Continuous fever Continuous fever is a type or pattern of fever in which temperature does not touch the baseline and remains above normal throughout the day. The variation between maximum and minimum temperature in 24 hours is less than 1°C (1.5°F). It usually o ...
, where temperature remains above normal and does not fluctuate more than in 24 hours (e.g. in
bacterial pneumonia Bacterial pneumonia is a type of pneumonia caused by bacterial infection. Types Gram-positive ''Streptococcus pneumoniae'' () is the most common bacterial cause of pneumonia in all age groups except newborn infants. ''Streptococcus pneumoniae'' ...
,
typhoid Typhoid fever, also known as typhoid, is a disease caused by '' Salmonella'' serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several ...
,
infective endocarditis Infective endocarditis is an infection of the inner surface of the heart, usually the valves. Signs and symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count. Complications ...
,
tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...
, or
typhus Typhus, also known as typhus fever, is a group of infectious diseases that include epidemic typhus, scrub typhus, and murine typhus. Common symptoms include fever, headache, and a rash. Typically these begin one to two weeks after exposure. ...
. *
Intermittent fever Intermittent fever is a type or pattern of fever in which there is an interval where temperature is elevated for several hours followed by an interval when temperature drops back to normal. This type of fever usually occurs during the course of an ...
is present only for a certain period, later cycling back to normal (e.g., in
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
,
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 ...
,
pyemia Pyaemia (or pyemia) is a type of sepsis that leads to widespread abscesses of a metastatic nature. It is usually caused by the staphylococcus bacteria by pus-forming organisms in the blood. Apart from the distinctive abscesses, pyaemia exhibits ...
,
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
, or
African trypanosomiasis African trypanosomiasis, also known as African sleeping sickness or simply sleeping sickness, is an insect-borne parasitic infection of humans and other animals. It is caused by the species ''Trypanosoma brucei''. Humans are infected by two typ ...
. *
Remittent fever Remittent fever is a type or pattern of fever in which temperature does not touch the baseline and remains above normal throughout the day. Daily variation in temperature is more than 1°C in 24 hours, which is also the main difference as compared ...
, where the temperature remains above normal throughout the day and fluctuates more than in 24 hours (e.g., in
infective endocarditis Infective endocarditis is an infection of the inner surface of the heart, usually the valves. Signs and symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count. Complications ...
or
brucellosis Brucellosis is a highly contagious zoonosis caused by ingestion of unpasteurized milk or undercooked meat from infected animals, or close contact with their secretions. It is also known as undulant fever, Malta fever, and Mediterranean fever. The ...
). *
Pel–Ebstein fever Pel–Ebstein fever is a rarely seen condition noted in patients with Hodgkin's lymphoma Hodgkin lymphoma (HL) is a type of lymphoma, in which cancer originates from a specific type of white blood cell called lymphocytes, where multinucleated R ...
is a cyclic fever that is rarely seen in patients with
Hodgkin's lymphoma Hodgkin lymphoma (HL) is a type of lymphoma, in which cancer originates from a specific type of white blood cell called lymphocytes, where multinucleated Reed–Sternberg cells (RS cells) are present in the patient's lymph nodes. The condition wa ...
. * Undulant fever, seen in
brucellosis Brucellosis is a highly contagious zoonosis caused by ingestion of unpasteurized milk or undercooked meat from infected animals, or close contact with their secretions. It is also known as undulant fever, Malta fever, and Mediterranean fever. The ...
. *
Typhoid fever Typhoid fever, also known as typhoid, is a disease caused by '' Salmonella'' serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several ...
is a
continuous fever Continuous fever is a type or pattern of fever in which temperature does not touch the baseline and remains above normal throughout the day. The variation between maximum and minimum temperature in 24 hours is less than 1°C (1.5°F). It usually o ...
showing a characteristic ''step-ladder pattern,'' a step-wise increase in temperature with a high plateau. Among the types of intermittent fever are ones specific to cases of malaria caused by different pathogens. These are: * Quotidian fever, with a 24-hour periodicity, typical of
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
caused by ''
Plasmodium knowlesi ''Plasmodium knowlesi'' is a parasite that causes malaria in humans and other primates. It is found throughout Southeast Asia, and is the most common cause of human malaria in Malaysia. Like other ''Plasmodium'' species, ''P. knowlesi'' has a li ...
'' (''P. knowlesi''); *
Tertian fever Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects humans and other animals. Malaria causes Signs and symptoms, symptoms that typically include fever, fatigue (medical), tiredness, vomiting, and headaches. In se ...
, with a 48-hour periodicity, typical of later course
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
caused by '' P. falciparum'', '' P. vivax'', or '' P. ovale''; *
Quartan fever Quartan fever is one of the four types of malaria which can be contracted by humans. It is specifically caused by the ''Plasmodium malariae'' species, one of the six species of the protozoan genus ''Plasmodium''. Quartan fever is a form of malaria ...
, with a 72-hour periodicity, typical of later course
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
caused by '' P. malariae''. In addition, there is disagreement regarding whether a specific fever pattern is associated with
Hodgkin's lymphoma Hodgkin lymphoma (HL) is a type of lymphoma, in which cancer originates from a specific type of white blood cell called lymphocytes, where multinucleated Reed–Sternberg cells (RS cells) are present in the patient's lymph nodes. The condition wa ...
—the
Pel–Ebstein fever Pel–Ebstein fever is a rarely seen condition noted in patients with Hodgkin's lymphoma Hodgkin lymphoma (HL) is a type of lymphoma, in which cancer originates from a specific type of white blood cell called lymphocytes, where multinucleated R ...
, with patients argued to present high temperature for one week, followed by low for the next week, and so on, where the generality of this pattern is debated. Persistent fever that cannot be explained after repeated routine clinical inquiries is called
fever of unknown origin Fever of unknown origin (FUO) refers to a condition in which the patient has an elevated temperature (fever) but, despite investigations by a physician, no explanation has been found.
. A
neutropenic fever Febrile neutropenia is the development of fever, often with other signs of infection, in a patient with neutropenia, an abnormally low number of neutrophil granulocytes (a type of white blood cell) in the blood. The term neutropenic sepsis is also ...
, also called febrile neutropenia, is a fever in the absence of normal immune system function. Because of the lack of infection-fighting
neutrophil 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 ...
s, a bacterial infection can spread rapidly; this fever is, therefore, usually considered to require urgent medical attention. This kind of fever is more commonly seen in people receiving immune-suppressing
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...
than in apparently healthy people.


Hyperpyrexia

Hyperpyrexia is an extreme elevation of
body temperature Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
which, depending upon the source, is classified as a
core body temperature Normal human body-temperature (normothermia, euthermia) is the typical temperature range found in humans. The normal human body temperature range is typically stated as . Human body temperature varies. It depends on sex, age, time of day, exert ...
greater than or equal to ; the range of hyperpyrexias includes cases considered severe (≥ 40 °C) and extreme (≥ 42 °C). It differs from
hyperthermia Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...
in that one's thermoregulatory system's set point for body temperature is set above normal, then heat is generated to achieve it. In contrast, hyperthermia involves body temperature rising above its set point due to outside factors. The high temperatures of hyperpyrexia are considered
medical emergencies A medical emergency is an acute injury or illness that poses an immediate risk to a person's life or long-term health, sometimes referred to as a situation risking "life or limb". These emergencies may require assistance from another, qualified p ...
, as they may indicate a serious underlying condition or lead to severe morbidity (including permanent
brain damage Neurotrauma, brain damage or brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating t ...
), or to death. A common cause of hyperpyrexia is an
intracranial hemorrhage Intracranial hemorrhage (ICH), also known as intracranial bleed, is bleeding within the skull. Subtypes are intracerebral bleeds ( intraventricular bleeds and intraparenchymal bleeds), subarachnoid bleeds, epidural bleeds, and subdural bleeds. ...
. Other causes in emergency room settings include
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
,
Kawasaki syndrome Kawasaki disease is a syndrome of unknown cause that results in a fever and mainly affects children under 5 years of age. It is a form of vasculitis, where blood vessels become inflamed throughout the body. The fever typically lasts for more tha ...
,Marx (2006), p. 2506.
neuroleptic malignant syndrome Neuroleptic malignant syndrome (NMS) is a rare but life-threatening reaction that can occur in response to neuroleptic or antipsychotic medication. Symptoms include high fever, confusion, rigid muscles, variable blood pressure, sweating, and fas ...
,
drug overdose A drug overdose (overdose or OD) is the ingestion or application of a drug or other substance in quantities much greater than are recommended.
,
serotonin syndrome Serotonin syndrome (SS) is a group of symptoms that may occur with the use of certain serotonergic medications or drugs. The degree of symptoms can range from mild to severe, including a potentiality of death. Symptoms in mild cases include high ...
, and
thyroid storm The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...
.


Differential diagnosis

Fever is a common
symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...
of many medical conditions: *
Infectious disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
, e.g.,
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
,
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, headache, vomiting, muscle and joint pains, and a characteristic ...
,
Ebola Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after becom ...
,
gastroenteritis Gastroenteritis, also known as infectious diarrhea and gastro, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydra ...
,
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
,
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 ...
,
Lyme disease 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 ...
,
rocky mountain spotted fever Rocky Mountain spotted fever (RMSF) is a bacterial disease spread by ticks. It typically begins with a fever and headache, which is followed a few days later with the development of a rash. The rash is generally made up of small spots of bleedin ...
,
secondary syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, and ...
,
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
, infectious mononucleosis, mononucleosis, as well as infections of the skin, e.g., abscesses and boils. * Immunology, Immunological diseases, e.g., relapsing polychondritis, autoimmune hepatitis, granulomatosis with polyangiitis, Horton disease, inflammatory bowel diseases, Kawasaki disease, lupus erythematosus, sarcoidosis, and Adult-onset Still's disease, Still's disease; * Tissue destruction, as a result of cerebral hemorrhage, cerebral bleeding, crush syndrome, hemolysis, infarction, rhabdomyolysis, surgery, etc.; * Cancers, particularly blood cancers such as leukemia and lymphomas; * Metabolic disorders, e.g., gout, and porphyria; and * Inherited metabolic disorder, e.g., Fabry disease. Adult and pediatric manifestations for the same disease may differ; for instance, in
COVID-19 Coronavirus disease 2019 (COVID-19) is a contagious disease caused by a virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The first known case was COVID-19 pandemic in Hubei, identified in Wuhan, China, in December ...
, one metastudy describes 92.8% of adults versus 43.9% of children presenting with fever. In addition, fever can result from a reaction to an incompatible blood product. Teething is not a cause of fever.


Function


Immune function

Fever is thought to contribute to host defense, as the reproduction of pathogens with strict temperature requirements can be hindered, and the rates of some important immunological reactions are increased by temperature. Fever has been described in teaching texts as assisting the healing process in various ways, including: :* increased mobility of leukocytes; :* enhanced leukocyte phagocytosis; :* decreased endotoxin effects; and :* increased Cell proliferation, proliferation of T cells.


Advantages and disadvantages

Having a fever response in response to an infectious disease is generally regarded as protective, whereas fever in non-infections may be maladaptive. Studies have not been consistent on whether treating fever generally worsens or improves mortality risk. Benefits or harms may depend on the type of infection, health status of the patient and other factors. Studies using warm-blooded vertebrates suggest that they recover more rapidly from infections or critical illness due to fever. In
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
, fever is associated with reduced mortality.


Pathophysiology of fever induction


Hypothalamus

Temperature is regulated in the hypothalamus. The trigger of a fever, called a pyrogen, results in the release of prostaglandin E2 (PGE2). PGE2 in turn acts on the hypothalamus, which creates a systemic response in the body, causing heat-generating effects to match a new higher temperature set point. There are four receptors in which PGE2 can bind (EP1-4), with a previous study showing the EP3 subtype is what mediates the fever response. Hence, the hypothalamus can be seen as working like a thermostat. When the set point is raised, the body increases its temperature through both active generation of heat and retention of heat. Peripheral vasoconstriction both reduces heat loss through the skin and causes the person to feel cold. Norepinephrine increases thermogenesis in brown adipose tissue, and muscle contraction through shivering raises the Basal metabolic rate, metabolic rate. If these measures are insufficient to make the blood temperature in the brain match the new set point in the hypothalamus, the brain orchestrates heat effector mechanisms via the autonomic nervous system or primary motor center for shivering. These may be: * Increased heat production by increased muscle tone, shivering (muscle movements to produce heat) and release of hormones like epinephrine; and * Prevention of heat loss, e.g., through vasoconstriction. When the hypothalamic set point moves back to baseline—either spontaneously or via medication—normal functions such as sweating, and the reverse of the foregoing processes (e.g., vasodilation, end of shivering, and nonshivering heat production) are used to cool the body to the new, lower setting. This contrasts with
hyperthermia Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...
, in which the normal setting remains, and the body overheats through undesirable retention of excess heat or over-production of heat. Hyperthermia is usually the result of an excessively hot environment (heat stroke) or an adverse reaction to drugs. Fever can be differentiated from hyperthermia by the circumstances surrounding it and its response to anti-pyretic medications. In infants, the autonomic nervous system may also activate brown adipose tissue to produce heat (non-exercise-associated thermogenesis, also known as non-shivering thermogenesis). Increased heart rate and vasoconstriction contribute to increased blood pressure in fever.


Pyrogens

A pyrogen is a substance that induces fever. In the presence of an infectious agent, such as bacteria, viruses, viroids, ''etc''., the immune response of the body is to inhibit their growth and eliminate them. The most common pyrogens are endotoxins, which are lipopolysaccharides (LPS) produced by Gram-negative bacteria such as ''Escherichia coli, E. coli.'' But pyrogens include non-endotoxic substances (derived from microorganisms other than gram-negative-bacteria or from chemical substances) as well. The types of pyrogens include internal (endogenous) and external (exogenous) to the body. The "pyrogenicity" of given pyrogens varies: in extreme cases, bacterial pyrogens can act as superantigens and cause rapid and dangerous fevers.


Endogenous

Endogenous pyrogens are cytokines released from monocytes (which are part of the immune system). In general, they stimulate chemical responses, often in the presence of an antigen, leading to a fever. Whilst they can be a product of external factors like exogenous pyrogens, they can also be induced by internal factors like damage associated molecular patterns such as cases like rheumatoid arthritis or lupus. Major endogenous pyrogens are interleukin 1 (α and β) and interleukin 6 (IL-6). Minor endogenous pyrogens include interleukin-8, Lymphotoxin alpha, tumor necrosis factor-β, macrophage inflammatory protein-α and macrophage inflammatory protein-β as well as interferon-α, IFN-β, interferon-β, and Interferon-gamma, interferon-γ. Tumor necrosis factor-α (TNF) also acts as a pyrogen, mediated by interleukin 1 (IL-1) release. These cytokine factors are released into general circulation, where they migrate to the brain's circumventricular organs where they are more easily absorbed than in areas protected by the blood–brain barrier. The cytokines then bind to endothelium, endothelial receptors on vessel walls to receptors on microglial cells, resulting in activation of the arachidonic acid pathway. Of these, IL-1β, TNF, and IL-6 are able to raise the temperature setpoint of an organism and cause fever. These proteins produce a cyclooxygenase which induces the hypothalamic production of PGE2 which then stimulates the release of neurotransmitters such as cyclic adenosine monophosphate and increases body temperature.


Exogenous

Exogenous pyrogens are external to the body and are of microbial origin. In general, these pyrogens, including bacterial cell wall products, may act on Toll-like receptors in the hypothalamus and elevate the thermoregulatory setpoint. An example of a class of exogenous pyrogens are bacterial lipopolysaccharides (LPS) present in the cell wall of gram-negative bacteria. According to one mechanism of pyrogen action, an immune system protein, lipopolysaccharide-binding protein (LBP), binds to LPS, and the LBP–LPS complex then binds to a CD14 receptor on a macrophage. The LBP-LPS binding to CD14 results in cellular synthesis and release of various endogenous cytokines, e.g., interleukin 1 (IL-1), interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNFα). A further downstream event is activation of the arachidonic acid pathway.


PGE2 release

PGE2 release comes from the arachidonic acid pathway. This pathway (as it relates to fever), is mediated by the enzymes phospholipase, phospholipase A2 (PLA2), cyclooxygenase, cyclooxygenase-2 (COX-2), and prostaglandin E2 synthase. These enzymes ultimately mediate the synthesis and release of PGE2. PGE2 is the ultimate mediator of the febrile response. The setpoint temperature of the body will remain elevated until PGE2 is no longer present. PGE2 acts on neurons in the preoptic area (POA) through the prostaglandin E receptor 3 (EP3). EP3-expressing neurons in the POA innervate the dorsomedial hypothalamus (DMH), the rostral raphe pallidus nucleus in the medulla oblongata (rRPa), and the paraventricular nucleus (PVN) of the hypothalamus. Fever signals sent to the DMH and rRPa lead to stimulation of the Sympathetic nervous system, sympathetic output system, which evokes non-shivering thermogenesis to produce body heat and skin vasoconstriction to decrease heat loss from the body surface. It is presumed that the innervation from the POA to the PVN mediates the neuroendocrine effects of fever through the pathway involving pituitary gland and various endocrine organs.


Management

Fever does not necessarily need to be treated, and most people with a fever recover without specific medical attention. Although it is unpleasant, fever rarely rises to a dangerous level even if untreated. Damage to the brain generally does not occur until temperatures reach , and it is rare for an untreated fever to exceed . Treating fever in people with
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
does not affect outcomes. Small trials have shown no benefit of treating fevers of or higher of critical ill patients in ICUs, and one trial was terminated early because patients receiving aggressive fever treatment were dying more often. According to the NIH, the two assumptions which are generally used to argue in favor of treating fevers have not been experimentally validated. These are that (1) a fever is noxious, and (2) suppression of a fever will reduce its noxious effect. Most of the other studies supporting the association of fever with poorer outcomes have been observational in nature. In theory, these critically ill patients and those faced with additional physiologic stress may benefit from fever reduction, but the evidence on both sides of the argument appears to be mostly equivocal.


Conservative measures

Limited evidence supports sponging or bathing feverish children with tepid water. The use of a mechanical fan, fan or air conditioning may somewhat reduce the temperature and increase comfort. If the temperature reaches the extremely high level of
hyperpyrexia Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
, aggressive cooling is required (generally produced mechanically via conduction (heat), conduction by applying numerous ice packs across most of the body or direct submersion in ice water). In general, people are advised to keep adequately hydrated. Whether increased fluid intake improves symptoms or shortens respiratory illnesses such as the
common cold The common cold or the cold is a viral infectious disease of the upper respiratory tract that primarily affects the respiratory mucosa of the nose, throat, sinuses, and larynx. Signs and symptoms may appear fewer than two days after exposu ...
is not known.


Medications

Medications that lower fevers are called ''antipyretics''. The antipyretic
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 ...
is effective in reducing fevers in children. It is more effective than acetaminophen (paracetamol) in children. Ibuprofen and acetaminophen may be safely used together in children with fevers. The efficacy of acetaminophen by itself in children with fevers has been questioned. Ibuprofen is also superior to aspirin in children with fevers. Additionally, aspirin is not recommended in children and young adults (those under the age of 16 or 19 depending on the country) due to the risk of Reye's syndrome. Using both paracetamol and ibuprofen at the same time or alternating between the two is more effective at decreasing fever than using only paracetamol or ibuprofen. It is not clear if it increases child comfort. Response or nonresponse to medications does not predict whether or not a child has a serious illness. With respect to the effect of antipyretics on the risk of death in those with infection, studies have found mixed results as of 2019. Animal models have found worsened outcomes with the use of antipyretics in influenza as of 2010 but they have not been studied for this use in humans.


Epidemiology

Fever is one of the most common
medical signs Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...
. It is part of about 30% of healthcare visits by children, and occurs in up to 75% of adults who are seriously sick. About 5% of people who go to an emergency room have a fever.


History

A number of types of fever were known as early as 460 BC to 370 BC when Hippocrates was practicing medicine including that due to
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
(tertian or every 2 days and quartan or every 3 days). It also became clear around this time that fever was a symptom of disease rather than a disease in and of itself. Infections presenting with fever were a major source of mortality in humans for about 200,000 years. Until the late nineteenth century, approximately half of all humans died from infections before the age of fifteen. An older term, :wikt:febricula, febricula (a diminutive form of the Latin language, Latin word for fever), was once used to refer to a low-grade fever lasting only a few days. This term fell out of use in the early 20th century, and the symptoms it referred to are now thought to have been caused mainly by various minor Virus, viral respiratory infections.


Society and culture


Mythology

*Febris (''fever'' in Latin) is the goddess of fever in Roman mythology. People with fevers would visit her temples. *Tertiana and Quartana are the goddesses of tertian and quartan fevers of malaria in Roman mythology. *Jvarasura (''fever-demon'' in Hindi) is the personification of fever and disease in Hindu mythology, Hindu and Buddhist mythology.


Paediatrics

Fever is often viewed with greater concern by parents and healthcare professionals than might be deserved, a phenomenon known as fever phobia, which is based in both caregiver's and parents' misconceptions about fever in children. Among them, many parents incorrectly believe that fever is a disease rather than a medical sign, that even low fevers are harmful, and that any temperature even briefly or slightly above the oversimplified "normal" number marked on a thermometer is a clinically significant fever. They are also afraid of harmless side effects like
febrile seizure A febrile seizure, also known as a fever fit or febrile convulsion, is a seizure associated with an increased body temperature but without any intracranial infection. Febrile seizures affect 2–7% of children and are more common in boys than gi ...
s and dramatically overestimate the likelihood of permanent damage from typical fevers. The underlying problem, according to professor of pediatrics Barton D. Schmitt, is that "as parents we tend to suspect that our children's brains may melt." As a result of these misconceptions parents are anxious, give the child fever-reducing medicine when the temperature is technically normal or only slightly elevated, and interfere with the child's sleep to give the child more medicine.


Other species

Fever is an important metric for the medical diagnosis, diagnosis of livestock disease, disease in domestic animals. The body temperature of animals, which is taken rectally, is different from one species to another. For example, a horse is said to have a fever above (). In species that allow the body to have a wide range of "normal" temperatures, such as camels, whose body temperature varies as the environmental temperature varies, the body temperature which constitutes a febrile state differs depending on the environmental temperature. Fever can also be behaviorally induced by invertebrates that do not have immune-system based fever. For instance, some species of grasshopper will thermoregulate to achieve body temperatures that are 2–5 °C higher than normal in order to inhibit the growth of fungal pathogens such as ''Beauveria bassiana'' and ''Metarhizium acridum''. Honeybee colonies are also able to induce a fever in response to a fungal parasite ''Ascosphaera apis''.


References


Further reading

*


External links


Fever and Taking Your Child's Temperature



Drugs most commonly associated with the adverse event Pyrexia (Fever) as reported the FDA


at MedlinePlus

at ''The New York Times'' {{Authority control Fever, Wikipedia medicine articles ready to translate Wikipedia emergency medicine articles ready to translate Symptoms and signs