About a year ago, an Airbnb guest stayed for 2 weeks and left us with bedbugs that bit my daughter multiple times. We exterminated them and everything was fine for a while.
When another guest got bitten this summer, Airbnb refunded the guest more than 50% of her rent, even though I had a strict refund policy and denied their request for a refund since I know they started the new infestation!
If you can avoid it, do not host with Airbnb. Work with Craigslist, Zillow or other agencies or sites who let you make your own rules for when bad things happen.