A Bug

Vivian has had an upset stomach for a few days now and keeps asking why her stomach hurts.  I told her she probably had a little bug and needs to rest and drink.
She asked me again a little later and I said, "remember, it's probably a little bug?"
"Or a fly," she told me.
"Um, I think a bug, which means a little sickness."
"Right. Like a fly. Probably a mosquito.  Remember mosquitoes make big bites on me? I think one did it inside my stomach.  I have a mosquito."
"Perhaps."