For years they've been telling us to not spread viruses. Wash your hands, cover your mouth when you cough, and whatever you do, don't let the dog lick your face.
I've figured out the reason for this zealousness - spreading viruses can be alot of fun! Take this game for example. It's probably not supported by the Center for Disease Control, and I'm sure it's not supported by the center for fun control, but it earns the Cybersalt stamp of approval.