..... I know, strongly, that this is purely an anecdote.
But this was kind of crazy to see. In Dec 2019 my family and I traveled from Europe to visit family in Maine. We returned around new year's and all got what was by _far_ the worst flu any of us had every had in our lives. And weirdest - it was consistent with covid symptoms.
My youngest was 2 months old (we flew back with her to meet family) and she was quite ill - we still suspect long covid affects her.
Now, entirely possible this is confirmation bias, and airports would have been full of travellers from all over, not just Maine, but still...