Notice they didn’t say WHERE the infected mosquito was when the illegal was bitten - Guatemala? Nicaragua? Guyana?
And YES. ILLEGAL.
I have seen the kids on the international flights coming into America with unbroken chicken pox bumps and no one said a damn word.
"Locally acquired" seems to imply that it was here. Of course, a local mosquito had to get the virus from someone, and that someone else may have brought it with them, so the mosquito could re-infect someone else on a subsequent feeding.