Another interesting field, which is my own, is cofactors, not only to the disease but also to transmission. I am still puzzled by the fact that you get more sexual transmission in some ethnic populations. One way to answer this is to look for genetic factors. ↗
It is a monstrous thing that I will say, but I will say it all the same: I find in many things more restraint and order in my morals than in my opinions, and my lust less depraved than my reason. ↗