Fever facts for kids
A fever is when a person's body temperature is hotter than 37.5 degrees Celsius (99.5 Fahrenheit). Normal body temperature for humans varies based on a variety of factors, including age and level of physical activity. It is typically cited as 37 degrees Celsius (98.6 F), but naturally varies from person to person by at least .5 degrees Celsius. The actual measurement of body temperature will vary based on the location of the measurement. For a temperature taken from under the tongue, the measurement may be lower. Rectal temperatures will read about 0.3 C (0.55 F) higher, and armpit temperatures will read about the same amount lower.
When people are ill, their body's immune system fights the disease, and so the body temperature rises. Fever is a defensive measure of the body against the germs: the life cycles of the germs are disrupted when the body temperature rises.
About 38 °C (100.4 F) degrees is called a low-grade fever, and above 39 °C (103 F) degrees is a high-grade fever.
Children usually have a higher fever than adults; their immune system is less mature. Infants have the highest normal temperature, which decreases as people age. Some animals, especially small ones like rabbits and cats, also have a higher normal temperature than humans.
Sometimes, high-grade fever can be a medical emergency. At or above 42 °C (107.6 F) organs start taking damage that may not be repairable.
Contents
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 (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, febricula (a diminutive form of the 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 viral respiratory infections.
Associated symptoms
A fever is usually accompanied by sickness behavior, which consists of lethargy, depression, loss of appetite, sleepiness, hyperalgesia, 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 (which can also cause hallucinations) may also present itself during high fevers.
Types
Various patterns of measured patient temperatures have been observed, some of which may be indicative of a particular medical diagnosis:
- Continuous fever, where temperature remains above normal and does not fluctuate more than 1 °C in 24 hours (e.g. in bacterial pneumonia, typhoid fever, infective endocarditis, tuberculosis, or typhus).
- Intermittent fever is present only for a certain period, later cycling back to normal (e.g., in malaria, leishmaniasis, pyemia, sepsis, or African trypanosomiasis).
- Remittent fever, where the temperature remains above normal throughout the day and fluctuates more than 1 °C in 24 hours (e.g., in infective endocarditis or brucellosis).
- Pel–Ebstein fever is a cyclic fever that is rarely seen in patients with Hodgkin's lymphoma.
- Undulant fever, seen in brucellosis.
- Typhoid fever is a continuous fever 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 caused by Plasmodium knowlesi (P. knowlesi);
- Tertian fever, with a 48-hour periodicity, typical of later course malaria caused by P. falciparum, P. vivax, or P. ovale;
- Quartan fever, with a 72-hour periodicity, typical of later course malaria caused by P. malariae.
In addition, there is disagreement regarding whether a specific fever pattern is associated with Hodgkin's lymphoma—the Pel–Ebstein fever, 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. A neutropenic fever, also called febrile neutropenia, is a fever in the absence of normal immune system function. Because of the lack of infection-fighting neutrophils, 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 than in apparently healthy people.
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 42.0 °C (107.6 °F), and it is rare for an untreated fever to exceed 40.6 °C (105.1 °F).
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 fan or air conditioning may somewhat reduce the temperature and increase comfort. If the temperature reaches the extremely high level of hyperpyrexia, aggressive cooling is required (generally produced mechanically via 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 is not known.
Medications
Medications that lower fevers are called antipyretics. The antipyretic ibuprofen 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.
Differential diagnosis
Fever is a common symptom of many medical conditions:
- Infectious disease, e.g., COVID-19, dengue, Ebola, gastroenteritis, HIV, influenza, Lyme disease, rocky mountain spotted fever, malaria, mononucleosis, as well as infections of the skin, e.g., abscesses and boils.
- Immunological diseases, e.g., relapsing polychondritis, autoimmune hepatitis, granulomatosis with polyangiitis, Horton disease, inflammatory bowel diseases, Kawasaki disease, lupus erythematosus, sarcoidosis, Still's disease, rheumatoid arthritis, lymphoproliferative disorders and psoriasis;
- Tissue destruction, as a result of 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, 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.
See also
In Spanish: Fiebre para niños
