Fever, or pyrexia, is a body temperature that is elevated above the normal range: normal oral temperatures range from 98.6¡ F (37¡ C) in persons confined to bed to 99.0¡ F (37.4¡ C) in active persons; temperatures taken rectally usually register slightly higher. Body temperature is usually kept within the normal range by several mechanisms, which are controlled and integrated mainly in the hypothalamus region of the brain. Fever is not a disease itself but a symptom of disease. It is a sign of infectious disease, such as pneumonia, and may accompany certain kinds of cancers, a stroke or heart attack, and various other disorders. Because many microorganisms cannot survive elevated temperatures, fever is generally considered a defense mechanism against infections. Temperatures above 112¡ F (44.5¡ C) are usually fatal because they cause irreversible damage to the nervous system. In most cases, fever can be reduced by aspirin or other fever-reducing drugs, called antipyretics.