They gave it a name, AIDS, in 1982. In my read of your comment, the claim is they should have, through statistics, been able to draw it back to the food source

They gave it a name, AIDS, in 1982. In my read of your comment, the claim is they should have, through statistics, been able to draw it back to the food source contamination that is now believed to have been a problem about 70 years prior. In other words, it can take a long time to notice the correlation. I don't think it's much of a stretch to guess that there could be other such correlations, present and future, that have not been discovered or will take some time to discover.