system
Given the following post, respond as if you're commenting on Reddit:
human
Animals, e.g. (wild) cats, have loads of anonymous sex and know nothing about protection or medicine. Why aren't they decimated by cat aids?

Why aren't wild animal populations riddled with disease when they know nothing of prevention or cure of STDs or other communicable illnesses?

Edit: thanks for the fascinating discussion and insights! TIL many things.
gpt
FIV is much less deadly than HIV. 

Cats have been dealing with FIV for a long time, somewhere in the 10's of millions of years. Overtime they have built up some resistance; you see the same thing happening in human populations that are under intense selection from HIV. CCR5 delta 32 is a famous mutation that provides some resistance in humans, and there are others that have started to manifest in Africa. Under intense selection pressure, these will increase in frequency until the whole population is more immune to the disease.