ELi5 Why are fevers so dangerous? If they’re an immune system mechanism, shouldn’t there also be a biological “emergency stop/ brain overheating” button?
In: Biology
Fevers work because they heat your core body temperature up enough that some foreign bacteria and viruses cannot survive at that temperature so they die. Fevers can also kill cells your body produces which makes fevers as harmful as they can be helpful.
Evolution works by selecting things that work more often than things that don’t. If 10 people get sick with the flu, 5 get a fever and 5 don’t get a fever and 3 of the 5 without a fever die compared to 1 of the 5 that get a fever die as a result of the fever than what that means is you now have 6 people left, 4 of which that have the gene to have a fever and 2 of which that don’t. So now you have twice as many people with a gene selected to have a fever when sick than you do those that don’t. That then gets passed down to their offspring who then are more likely to survive infections and sickness than those offspring who don’t. Repeat this over enough generations and you get a population of people who are more likely to get fevers even though that can be harmful. Some of them may die as a result of the fever but most won’t.
In essence fevers work by making your body hot enough to kill some bad cells/viruses but might also hurt good cells. But it does more damage to bad cells than it does good cells most of the time. So you’re more likely to survive than those who don’t have fevers. Those who survive pass their genes onto the next generation and they then pass that gene onto their next generation making more people who have fevers than people who don’t have fevers.
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