[L. febris]

1. Abnormal elevation of temperature.
The normal temperature taken orally ranges from about 97.6° to 99.6°F, although there is individual variation. Rectal temperature is 0.5° to 1.0°F higher than oral temperature. Normal temperature fluctuates during the day and is lowest in the morning and highest in the late afternoon; these variations are maintained during a fever. The expended basal energy is estimated to be increased about 12% for each degree centigrade of fever.
SYN: pyrexia
See: basal energy expenditure; temperature

ETIOLOGY
Fever is resetting at a higher level the temperature that the body seeks to maintain . It is caused by the release of interleukin-1 (IL-1), interleukin-2 (IL-2), and tumor necrosis factor from white blood cells (esp. macrophages), secretion of acute phase proteins, and redistribution of the blood away from the skin by the autonomic nervous system. The body cools itself and returns its temperature to normal range by diaphoresis (sweating). Elevated temperature caused by inadequate thermoregulatory responses during exercise in very hot weather is called hyperthermia; the set point is not increased. Infections, drugs, tumors, breakdown of necrotic tissue, CNS damage, and collagen diseases are the underlying causes of fevers. Despite common beliefs, fever is not harmful except in patients who cannot tolerate its hypermetabolic effects, some older patients in whom it can cause delirium, and children with a history of febrile seizures.

PATIENT CARE
Patients with febrile illnesses frequently seek professional medical attention. Fever is often an important indicator of infections or inflammations that may cause significant injury if left untreated. Diagnosing the cause of a fever may lead to specific therapies that limit the duration of an illness, prevent secondary organ damage or, in some instances, death. The suppression of fever, however, is controversial. Some believe that fever helps to eradicate infecting organisms that cannot survive in a hot environment. Nonetheless, medications such as acetaminophen, aspirin, and other nonsteroidal anti-inflammatory drugs can lower body temperatures in febrile patients and are commonly used for that purpose esp. if the body temperature exceeds 101°F (38.5°C). Whether this usage results in improvements in survival or decreases in morbidity is unknown. In some settings (e.g., the care of the hospice patient with a fever) withholding an antipyretic drug is considered by most health care providers inadequate symptom management. In other settings (e.g., in patients with malignant hyperthermia or heatstroke), giving fever-suppressing treatment represents a standard of care. To date, however, controlled trials of withholding antipyretics in many illnesses have not been performed.

Fever suppression is also typically recommended for those who have suffered stroke or persistent seizures; however, proof of the effectiveness of lowering the body temperature of stroke victims is based on laboratory data rather than clinical effectiveness. Fever suppression in young children with viral and bacterial infections often provides a source of comfort; yet some researchers have speculated about adverse effects of this very common practice (e.g., whether fever suppression in children and autistic disorders are linked). When the choice is made to suppress a fever, it is probably most comfortable to give antipyretic drugs on a regular basis (every 4 or 6 hr) rather than intermittently. Intermittent dosing of antipyretics may produce alternating bouts of chills and sweats, which most patients find unpleasant. Some patients may never mount a fever; this is particularly true of people over 65, who may have serious treatable infections without elevations of body temperature. In older patients, the first indication of inflammatory or infectious illnesses may be a cough, lethargy, anorexia, or alterations in mental status.

Aspirin and other salicylates are contraindicated for use as antipyretics or analgesics in children because of their association with an increased risk of Reye's syndrome. Public and parental education should be provided to make certain this knowledge is widely disseminated.

2. A disease characterized by an elevation of body temperature.
Specific diseases that contain the word “fever” and in which fever is a significant symptom are placed under the first word.
See: rheumatic fever; typhoid fever; yellow fever

Subentries:
brain fever
breakbone fever
childbed fever
continuous fever
dengue fever
drug fever
factitious fever
induced fever
intermittent fever
neutropenic fever
periodic fever
phlebotomus fever
relapsing fever
remittent fever
fever of unknown origin