Why do people get fevers when we get sick?

It’s a common misconception that pathogens, such as SARS-CoV-2 or the flu, cause fevers. But as biology professors, we know it’s not that simple. Pathogens cause fevers only indirectly.

When your immune system detects harmful microbes, your body raises its internal temperature to create a hostile environment. Turning up the heat suppresses the proliferation of invaders. In short, the fever is the body’s way of fighting back.

Although many people don’t understand fever’s purpose, animals certainly utilize it. Even so-called “simple creatures,” such as lizards, fish and insects, use fever to recover from illness.

Suppose you catch a virus. The immune system responds by releasing molecules called pyrogens, which induce fever. They signal the brain’s hypothalamus to raise the body’s set point temperature – like adjusting a thermostat.

Normal body temperature hovers around 98.6 degrees Fahrenheit (37 degrees Celsius), but fevers commonly increase temperatures to 100.4-104 F (38-40 C).

When that happens, your muscles contract,

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