My friend S. has twin boys. She told me that one of them has hand-foot-and-mouth disease, but that he had it on his butt. She told me that she'd asked the pediatrician, "Why don't they call it hand-foot-mouth-and-butt disease, then?"

Then she gave me a significant and expectant look, like she was waiting for me to acknowledge that her question was funny. When I didn't laugh, she went away.

She never told me what the pediatrician's answer was.

Apparently, hand-foot-and-mouth disease is commonly caused by coxsackievirus.

Coxsackievirus . . . now that's funny.