Editorial note: Bill, this question is not to be answered with bear puns. —LH
Oh, Infestation from a pangoro is quite unbearable, anonymous.
Bill, I swear to literally all the gods. —LH
In all seriousness, the pokémon themselves don’t do the infestation. Rather, they summon swarms of bugs that overwhelm their opponents. This is why it’s difficult to escape while the infestation is active: there are so many bugs swarming your pokémon that you simply can’t withdraw them.
Happy battling, anonymous!