system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What is the Bubonic Plague, and would it be as fatal today as it was in the Middle Ages?
gpt
Bubonic plague is a specific kind of disease caused by the bacteria Yersinia pestis. (Pneumonic and septicemic plague are the other kinds, less famous because they didn't destroy Europe.) Yersinia lives in fleas, which live on rodents. As a result, plague was able to spread very quickly in a time when sailors could bring rats across the Mediterranean, and when huge numbers of people lived in crowded, filthy cities where parasites were a normal part of life.

Is it as deadly now? No. Antibiotics have made plague dramatically more survivable, while hygiene in the developed world means you're highly unlikely to get fleas. In fact, when plague was found in squirrels near Los Angeles, the only response was to close a few campgrounds. There are many fine things to worry about, but the Black Death isn't one of them.