Why do animals (including people) get a fever when they get sick? What is the purpose?

Question

I've heard of two purposes for fevers. The most common explanation is that it over-heats the pathogen. But it over-heats your body, too. So is it worth it, risking damage or even death to warm up some germs when it might not even kill them? Why would they be able to tolerate less heat than your own cells? If anything, the bacteria and viruses shoud be more hardy, shouldn't they? The other explanation I've heard is that the immune system works better in the higher temperature. Is that the case? Or is it both of them, or neither one?

Answer 1

Wimpy pathogen. Tough human. Warmed up, hit bad bacteria harder. Snort! Regards, Larry.

Answer 2

Actually, its both. Your metabolism speeds up when you have a fever and are fighting an infection, and your immune system works at a faster pace, both inventing and multiplying antigens. Also, the fever is to kill the germs. It doesn't hurt you as much as it hurts the germs, because you have a cooler-than-body-temperature environment to offload heat, and because you have many more cells than a germ, if you lose a few at the source of infection, you won't die. All of this means a larger protein consumption by your system, so its good to eat some protein if you have an infection.

Answer 3

It seems like fever is designed to help the body kill off the infecting germs.  All life forms have a preferred range of temperature at which they are happiest and most reproductive.  If the body can shift temperature to a level that slows or stops reproduction, the body effectively limits or stops the disease process.  Usually the slowing along with the immune system are successful in killing the infecting bugs.

I did a search: "function of fever" and that led me to this website:

http://www.pbs.org/wgbh/evolution/librar...

that explained this better than I can.  You might want to follow some of the other links to see whether they have good answers for you too.