When you think about diseases like bubonic plague, you probably assume that’s not the sort of thing we have to worry about anymore.

But everything old is new again, and whether it’s thanks to anti-vaxxers, melting permafrost, or happenstance, that goes for viruses and bacteria, too.

Recently, the Associated Press says that health officials in Oregon have found a case of bubonic plague – otherwise known as the Black Death – in an adult male.

They say he got it from his pet, a cat that did not survive.

The plague is caused by Yersinia pestis, a bacteria that lives in rodents and their fleas. It infects lymph nodes, causing a fever and a headache, and left untreated, can spread into the bloodstream.

It’s considered rare in humans these days, but an unfortunate handful of Americans do contract it every year. Between 200 and 700 cases are reported across the world every year, but almost all of them survive, thanks to antibiotics.

In the world before antibiotics, the “black death” managed to wipe out around 30% of Europe’s entire population – around 20 million people.

By the 17th century, people had caught on that staying away from the infected could help contain the plague, and that helped quite a bit.

Nowadays, tough, how would your cat catch such a thing?

If you live in states like Arizona, California, New Mexico, Nevada, Oregon, and Colorado, they would catch it the same way animals did in the Middle Ages – by encountering infected vermin or their blood-carrying fleas.

The symptoms to look out for are wide-ranging and common – fever, loss of appetite, etc. – which means it can be hard to catch in time to save their lives.

Hopefully the doctors in those areas are sharp enough to remember to test humans in time, though.

Finger’s crossed.

Thought that was fascinating? Here’s another story you might like: Why You’ll Never See A Great White Shark In An Aquarium