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
It all boils down to evolution is based on “eh, it works, mostly”.
If the trait works more often than not, and can be passed down to offspring, then the environment “selects” that version.
Fevers are a trait for fighting infection that works… mostly. When it doesn’t work, the individual usually dies. So, there is no reason for a “stop…too much” trait to develop. It works and you live to make babies or you die and don’t.
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.
There is, at least in kids. All my kids (and I) had febrile seizures: when their temperature spiked they had a seizure (twitching, foaming at the mouth, losing consciousness, the works) and core temp immediately plummeted. My daughter had at least 20 of these. They’re scary the first couple of times you see them, but very effective in truncating the fever. Most people outgrow them by puberty if not well before.
All living organisms (that we know of) are made up of proteins – many many many proteins. All proteins have a maximum temperature they can survive before they literally unravel and die.
The body eventually figured out that if it raised its own temperature, it will exceed the temp at which the bacteria can survive, and they’ll die, and infection cured. Problem is that the temperature most bacteria die at, and the temperature the cells in your own body die at, is… pretty close.
So a runaway fever can literally bake you to death, because the body’s fever-regulating mechanism kinda got left in alpha and never got debugged. So, a fever up to 101-102 is… not great, but not fatal, but if it goes any higher than that, it sure as shit can be.
It is… yet another argument against intelligent design, frankly. But that’s what tylenol is for!
You know how you get viruses and bacteria all the time but fungal illnesses aren’t really a thing ever? Beyond annnoying external itchy stuff? fever basically wiped out internal fungal infections in mammals. It’s near nonexistent.
so you get the “why do I need all this stupid fever, I never get diseases that it helps on” but you never get the diseases it helps on because you are so good at fevers the diseases never happen. But give up fevers and mold is still everywhere and would love to grow mushrooms in every cut and infected wound
They actually generally aren’t. Unless you have brain damage, a fever (actual fever, not being caught in the sun and getting heat stroke) won’t get high enough to injure or kill you through overheating (contrary to popular belief). What can be a problem is fever causing dehydration, increased energy use and generally making you feel terrible.
Fevers are almost never dangerous. The underlying infection can be dangerous, but for the most part the rise in body temperature is dangerous for a small number of little kids (below 3) and a VERY small number of adults.
There’s even some data to suggest that people including kids have better outcomes if you give them no treatment for the fever at all. Again, we aren’t talking about other things that happen when people get sick, just the elevated temperature.
People think fevers are far more dangerous than they actually are.
In another few billion years there probably will be, unless the andromeda galaxy smashes into us first.
This was mentioned before but in too many words so I will summarize it; fever is not dangerous.
The problem is that diseases don’t just stop. Therefore your immune system can’t either.
Fevers generally are very powerful and helpful. If your body with a 40 degree fever isn’t going to kill the disease, the disease probably won’t go anywhere anytime soon, and you’re dead anyways. Better to just send it until one of you dies rather than ensure that the body dies to the disease eventually
Latest Answers