infectious diseases
Fever
Introduction
Fever is an elevated body temperature that occurs when the body's thermostat (located in the hypothalamus) resets at a higher temperature, primarily in response to an infection. Elevated body temperature that is not caused by a resetting of the temperature set point is called hyperthermia. Normal body temperature varies by Site of measurement Time of day The most common sites at which temperature is measured are the oral cavity and the rectum. Other sites include the tympanic membrane, the skin of the forehead, and much less preferably, the skin of the axilla. Rectal and tympanic membrane temperatures are about 0.6° Chigherthan oral temperatures, whereas skin temperatures are about 0.6° Clower. Oral and rectal temperature is now typically measured using an electronic thermometer; older mercury thermometers take longer to equilibrate and are more difficult to read. Forehead and tympanic membrane temperature is typically measured using an infrared scanning device. During a 24-hour period, temperature varies from lowest levels in the early morning to highest in late afternoon. Maximum variation is about 0.6°C. Oral temperatures are defined as elevated when they are: ≥ 37.2° C in the early morning OR ≥ 37.8° C at any time after the early morning OR Higher than a person’s known normal daily value These cutoffs are adjusted as above when temperature is measured from other sites. Many patients use “fever” very loosely, often meaning that they feel too warm, too cold, or sweaty, but they have not actually measured their temperature. Symptoms are due mainly to the condition causing the fever, although fever itself can cause chills, sweats, and discomfort and make patients feel flushed and warm. 