Yersinia Pestis is a bacterium, not a virus, and it can be killed by antibiotics. It's not gone. It's still around in fleas that live on squirrels and rats. In the mountains near where I live, the squirrels have it, and people get it every couple years.

But that may or may not be what caused the black death in medieval Europe, in my view. There's reason to think it might have been a really nasty hemorhagic virus like Ebola. See: https://history.howstuffworks.com/historical-events/black-de...