This is what I’m thinking. We had these all over Georgia. They swarmed in incredible numbers. They were considered harmless.
So it’s not the bugs that are new to the US. It’s the disease.
Well, the bugs have to contract the disease from somewhere before they can pass it on to humans.
Modern building techniques, modern plumbing, and modern waste removal have mitigated most of the breeding grounds for the disease here in the USA. I would guess (with no factual support what so ever) that most of the cases being seen are from recent entrants to our country from areas where the disease is more common.
Box elder bugs look similar, but they aren’t Chaga’s bugs.