fever

—feverless, adj.

/fee"veuhr/, n.

1. an abnormal condition of the body, characterized by undue rise in temperature, quickening of the pulse, and disturbance of various body functions.

2. an abnormally high body temperature.

3. the number of degrees of such a temperature above the normal.

4. any of a group of diseases in which high temperature is a prominent symptom: scarlet fever.

5. intense nervous excitement: The audience was in a fever of anticipation.

v.t.

6. to affect with or as with fever: The excitement fevered him.

[bef. 1000; ME; OE fefer < L febr- (s. of febris) fever; reinforced by AF fevre, OF fievre < L, as above]

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I

or pyrexia

Abnormally high body temperature or a disease characterized by it.

It most often occurs with infection. Normal core body temperature, measured orally, does not exceed 99°F (37.2°C). Up to 105°F (40.6°C), fever causes weakness and is best treated with aspirin, acetaminophen, or other antipyretic drugs. At 108°F (42.2°C) or more, it can lead to convulsions and death. In treatment, it is important to know the underlying cause. Fever appears to be a defense against infectious disease, stimulating leukocytes and increasing antibody production and perhaps killing or inhibiting bacteria and viruses that live within a narrow temperature range.

II

(as used in expressions)

undulant fever

Mediterranean fever

Malta fever

dandy fever

breakbone fever

typhoid fever

hay fever

hemorrhagic fever

swine fever

glandular fever

puerperal fever

childbed fever

relapsing fever

rheumatic fever

Rocky Mountain spotted fever

scarlet fever

yellow fever

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▪ pathology

also called  pyrexia 

      abnormally high bodily temperature (body heat) or a disease of which an abnormally high temperature is characteristic. Although most often associated with infection, fever is also observed in other pathologic states, such as cancer, coronary artery occlusion, and disorders of the blood. It also may result from physiological stresses, such as strenuous exercise or ovulation, or from environmentally induced heat exhaustion or heat stroke.

      Under normal conditions the temperature of deeper portions of the head and trunk does not vary by more than 1°–2° F in a day, and it does not exceed 99° F (37.22° C) in the mouth or 99.6° F (37.55° C) in the rectum. Fever can be defined as any elevation of body temperature above the normal level. Persons with fever may experience daily fluctuations of 5°–9° F above normal; peak levels tend to occur in the late afternoon. Mild or moderate states of fever (up to 105° F [40.55° C]) cause weakness or exhaustion but are not in themselves a serious threat to health. More serious fevers, in which body temperatures rise to 108° F (42.22° C) or more, can result in convulsions and death.

      During fever the blood and urine volumes become reduced as a result of loss of water through increased perspiration. Body protein is rapidly broken down, leading to increased excretion of nitrogenous products in the urine. When the body temperature is rising rapidly the affected person may feel chilly, or even have a shaking chill; conversely, when the temperature is declining rapidly the person may feel warm and have a flushed moist skin.

      In treating fever, it is important to determine the underlying cause of the condition. Mild and moderate fevers are best treated by aspirin or other antipyretic drugs, which exert their effect on the temperature-regulating areas of the brain.

      The mechanism of fever appears to be a defensive reaction by the body against infectious disease. When bacteria or viruses invade the body and cause tissue injury, one of the immune system's responses is to produce pyrogens. These chemicals are carried by the blood to the brain, where they disturb the functioning of the hypothalamus, the part of the brain that regulates body temperature. The pyrogens inhibit heat-sensing neurons and excite cold-sensing ones, and the altering of these temperature sensors deceives the hypothalamus into thinking the body is cooler than it actually is. In response the hypothalamus raises the body's temperature above the normal range, thereby causing a fever. The above-normal temperatures are thought to help defend against microbial invasion because they stimulate the motion, activity, and multiplication of white blood cells and increase the production of antibodies. At the same time, elevated heat levels may directly kill or inhibit the growth of some bacteria and viruses that can tolerate only a narrow temperature range.

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