Streptococcus is a common bacteria that's usually found in your throat, and if you've ever had strep throat or bronchial pneumonia you've had some experience with it. Streptococci can also cause contagious skin infections, including impetigo (a rash that most often affects pre-school kids and babies). It can also cause an invasive, serious skin infection called necrotizing fasciitis (also known as "flesh-eating" bacteria). And here's the worst news: About 39 percent of toilet seats harbor this nasty bug [source: Shoemaker].
So, are we really talking about flesh-eating bacteria lying in wait on a public toilet seat? While it's possible you could contract such an infection from a shared seat, it's highly unlikely. Only about 1 percent of adults carry the strep bacteria on their skin or in their throat, and it's estimated that you're more likely -- at least 50 percent more likely -- to be struck by lightning this year than to develop such an infection [source: Paediactrics & Child Health].