It turns out "cooties" are actually a real thing, and you really can get them by touching people: https://en.wikipedia.org/wiki/Cooties#/media/File:South_Bend_News-Times,_April_7,_1922.JPG …
And the infamous poison Zyklon B, which the Nazis used to kill people in extermination camps, was originally for killing cooties. Of course these days we have much better pesticides, and have made cooties almost an imaginary object, at least in the first world. Almost.