So, this new Black Death plague has appeared in a certain place called Dardeling. If you click in the Situation alert, and therefore you open the Situation panel, you'll get to know where the place is, and how the Black Death progresses:

Dardeling is the place where the plague started - could be worse, right?

Some months, maybe a year, since the plague started. It's getting closer...

After some time, the Black Death may end up reaching your country:

The Black Death has arrived in Poland! And while we're busy fighting the Teutonic Order in a war!