This is a little side note, but interesting if one is in to researching said things....

Speaking of HIV there is some strong but circumstantial evidence that it has actually been around for a long time, but it didn't actually become a problem for humans until we eliminated smallpox.

A little background...there was a couple of cases of people who were identified in to 60s as having it.

So apparently the HIV virus is much less likely to infect those that have had a recent smallpox vaccination, but we stopped giving those out widespread at the end of the 70s.

There is some thought that the HIV virus is unable to bind to the receptors needed if you have either

1. Had smallpox and lived and recovered
2. Had cowpox or some other virus that gave degrees of limited immunity
3. Were innoculated or vaccinated for smallpox

It is interesting because we see something similar with Covid, apparently there is a type of TB vaccine where if you have has it your odds are 60x less likely to contract Rona and develop Covid.