In my freshman year at the University of Minnesota, back in the depths of antediluvian time (1948-49), I took a course called "Public Health 101" or some such name.
Marvelous lecturer. He spoke from an outline, and he followed his outline! (Mirabile dictu!) He might say, "XYZ comes in three parts", and I'd write down,
XYZ and below it, 1 2 3 with space between. He would explain 1, then 2, then 3. Then he'd proceed to the next topic. Because he was SO organized, my notes were a wonderful reflection of his lectures. I know that I could repeat his first three lectures almost verbatim for years.
So what's that got to do with toilet seats?
He was discussing avenues of infection, and he discussed fomites. (FO-mi-tees). What are fomites? They are objects, such as a drinking glass, a doorknob, or a toilet seat.
He told us that it is RARE if not nonexistent to catch a venereal disease from fomites, "much to the dismay of those who want to claim that they got their gonorrhea or syphilis from a toilet seat". The infectious agents are highly susceptible to drying. If a sufferer "left something" on a toilet seat and another user came along immediately and sat down on a wet deposit, it just might be able to "catch", but even then it's highly unlikely.
Because of his great lecture organization and my resultant good notes, I got an A in the course, I'm pleased to say.