Bubonic plague killed at least one-third of the population of Europe between 1346 and 1353. But that was before we knew it was caused by the bacterium Yersina pestis.
Bubonic plague does still occasionally occur in small flare-ups of a few dozen cases, but we have antibiotics to treat it now. Plus, better hygiene makes it very hard for a disease spread by flea bites to become a global pandemic again.
Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.