During the yearly Ladybug invasion they end up everywhere. They usually show up around Oct 1 & leave when we get a really good hard freeze. I've had leaves fall into the pot, the dog licking the ball valve, flies inside & out, gnats in the airlock.
Even found a few gnats & a ladybug in an airlock inside my chest freezer. I have no idea how gnats & ladybugs could survive, number one the cold in there & all the CO2. I put a fan on it to mix before I stick my head down in there to pull our carboys.
It's hard to infect beer.