Yesterday I saw a little girl in a second grade classroom perform the most thorough display of self-contamination I’ve seen in my life. You’ve probably seen children make this face before: Two fingers go into the outer corners of your eyes, two in your nose, and two in your mouth, then you pull your two hands away from each other. You end up with slanted eyes, a wide nose and mouth, and hundreds of tiny bacteria and viruses* being every so lovingly placed into all THREE mucus membranes.
There cannot exist a more efficient way to get sick.
(*Apparently the plural of the word virus is highly debated, so I went with Wikipedia.)