Remember that Brownsville and the entire southern tip of Texas are home to many winter Texans/snowbirds. Since the senior population are very likely to be some of the most at risk, *and* they tend to live in RV parks where they socialize a lot, this could become a big problem in those parts.
On further reflection, if I wanted to start an epidemic, or panic which could be just as useful, I’d do it in southern Texas and at a time the snowbirds were returning home to all parts of the US and Canada. It’s a bit late in that cycle now, but the yearly migration is not over yet.