When I became a Catholic 12 years ago, I raised this issue with a Deacon. I was told that the alcohol in the wine killed germs.
In any event, I’ve never picked up anything from the cup.
I think someone lipping the lower rim of the cup, in extreme cases, depending on the virus/bacteria etc, especially if they have a sore on that lower lip can transmit disease.
Also breath on that rim, TB is airborne dispersal, something deposited on the rim has enough time betwen others to infect another. And nobody will be able to correlate where you got it, or when.
Additionally, the alcohol in the wine, is not automatically swabbing the lower rim.
Of course, these are not especially great concerns for very healthy populations, but I’m not sure with illegal immigration in my neck of the woods that we are all a healthy TB free population.