People that have constant diarrhea for example can't go in pools. Yet pools you can chlorinate to actually kill the bacteria. You are much more likely to get

People that have constant diarrhea for example can't go in pools. Yet pools you can chlorinate to actually kill the bacteria. You are much more likely to get sick from someone coughing in a small confined space with you vs. if someone has diarrhea in the water next to you. An alien looking upon this world would probably think it strange and illogical that we are generally okay with the coughing scenario but not with the pool scenario.