There is some portion of the population of the US, estimated by some surveys around 25% that do not wash their hands after they defecate in a public rest room. Plain common sense seems to be disappearing. Keep that in mind when you go out in public.
Now that I am approaching 70, I notice my immune system is not as strong as it used to be.
One of the tricks I learned on commercial raft trips is that they always have a means for people to wash their hands before meals. I always bring a steel wash basin and soap. It prevents outbreaks of digestive problems. A small bottle of Chlorox can be used to put a few drops in the dish wash water.