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Fever in Adults: Overview

Man with fever holding thermometer

Fever

The normal body temperature is about 98.6°F but may vary by 0.9°F to 1.8°F. In a healthy afebrile person, the hypothalamic thermoregulatory center of the brain regulates body temperature by balancing the heat produced during metabolism and that which is released during respiration and evaporation.

However, when this balance is offset due to different reasons, fever sets in.

What is fever?

  • Fever is considered a natural reaction when the body is ill and is one of the oldest indications of disease. It often occurs due to infection, inflammation, or trauma to the body. Because fever is a response of the body involving multi-systemic mechanisms that occur when the body is ill, it is considered a significant contributor to the pathogenesis, clinical presentation, and outcome of many illnesses and diseases.

  • Fever Duration
    Acute < 7 days and characteristic of most infectious diseases.
    Subacute Not more than 2 weeks and seen in certain infections such as typhoid fever.
    Chronic Also know as persistent fever lasting for > 2 weeks and typical in chronic bacterical infections such a tuberculosis, cancres, and viral infections like HIV. 

    Fevers can also have specific patterns depending on cause, and this, together with other signs and symptoms, is used to diagnose the underlying disease, infection, or condition.

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