eli5 why do your muscles and bones ache with illness such as flu?


eli5 why do your muscles and bones ache with illness such as flu?

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Minor aches are usually the result of inflammation. You’re familiar with inflammation in the context of minor injuries. If you get a cut, you’ll see the skin around the cut turn red and swell up, but what you won’t see is that your body is directing lots of extra white blood cells to the area to patrol for potential infection.

How much things swell up, and how much the body produces and directs extra white blood cells, is controlled by chemicals called cytokines. Some of them are *pro-inflammatory*, and ramp the level of immune activity up. Some are *anti-inflammatory*, and ramp it down.

Under normal circumstances, your body tries to regulate your immune response to a level that is enough to fight off infection, but not so much that there’s collateral damage done by your white blood cells (which are sort of the SWAT team of your body and which can mistakenly damage healthy cells sometimes). But when you’re sick, your body releases tons of pro-inflammatory cytokines. That ramps up the activity of your immune system in order to fight the infection. But in the process, it also ramps up any existing inflammation, and the increased swelling irritates your nerves, causing minor aches that you normally don’t notice to become significantly worse.

The virus isn’t just in the lungs, the coughs and sneezes are just how your lungs react to the virus – the rest of your body will react to the virus trying to fight it in all the other tissues, and in some tissues – muscles mainly – this response causes inflammation, aches and pains.