All geeks love science jokes (one of my favorites: what’s purple and drives to work? Answer: an Abelian grape [explanation, the elements of an Abelian group commute, i.e., a + b = b + a]).
Science jokes are good. You can learn some science from them. In particular, the first three or four of this set of groaners involve viruses and infectious diseases and each tell you — vividly — an important truth. The rest are pretty good, too.
Enjoy (hat tip Boingboing):