Fever and Chills: Causes

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Exploring the causes behind fever and chills during the flu

A viral flu infection can often present with a high fever1 associated with chills.2 Here we take a closer look at the reasons behind why fever and chills are a symptom of the flu.

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Fever and chills as a response to infection

Fever and associated chills are not an illness in themselves, but are, in fact, a physiological mechanism in response to viral or bacterial infection. The presence of a fever may actually serve as a beneficial symptom that helps to fight off the infection.3

  • Fever

    Man with red nose

    Fever as a symptom of the flu

    Fever is a normal defensive response to an active infection, the most common pathogens being bacterial or viral.3 The degree of fever may not directly correlate with the severity of the infection,3 and especially in children, even a mild illness can cause a high fever.2

    The anterior hypothalamus in the brain is responsible for regulating the set-point for the core body temperature, typically at 37°C in a healthy human body.4 A fever occurs when the hypothalamic temperature set-point rises to a higher temperature in response an infection.4 It is generally accepted that a temperature of 38°C or higher represents a fever.5

  • Chills

    Chills as a symptom of the flu

    Chills, also known as shivering, may occur at the beginning of either a bacterial or virus infection, typically accompanying a fever. Shivering may also result due to exposure to a cold environment.2

    Rapid muscle contraction and relaxation result in the shivering seen during chills, and is the body’s way of increasing its heat when it feels cold.2

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