Story from a doctor friend (actually, from her psychiatrist colleague).
It is often hard for people to deal with disease and some recently diagnosed HIV positive patients lash out: at the person who passed the virus to them, at family, friends or even society in general. A very small subgroup is of people who react by trying to infect as many other people as possible, often by engaging in unprotected sex with unknowing partner. This particular patient worked in a restaurant and decided that the big, industrial sized mayo was the perfect way to spread the virus, combining revenge with, ahem, happy time.
The doctor told us that it would probably be impossible for someone to contract HIV that way but eeewwweee, nevertheless. The patient was also going to be answering a few questions from the police.