Are Rats Really to Blame for the Black Death?

Rats get a bad rap, and deservedly so. They’re gross and carry a number of diseases.
And they’re infamously known for contributing to the spread of the Black Death, a plague pandemic that terrorized Europe in 1347 for five years and killed more than 20 million people.

Now, a new study is suggesting the possibility of a different scenario. The study proposes that human parasites like fleas and lice (also gross) were responsible for not only the spread of the plague, but the spread of a number of outbreaks from the 1300s to the 1800s (known as the Second Pandemic). Some historians have long believed rats were being unfairly blamed. According to the National Geographic:

For one, the Black Death tore through Europe far faster than any modern plague outbreaks. In addition, “rat falls” precede some modern outbreaks, but medieval plague records don’t mention rats dying en masse…If fleas and lice picked up the plague by biting an infected human, they could potentially hop onto a person in close quarters and transmit the disease.

The new study evaluated which model “best matched mortality patterns from nine different European plague outbreaks from the Second Pandemic. To their surprise, they found that in seven of the nine cities they examined, the human-parasite model more closely fit mortality records than the rat-flea model.”

What does this mean for the rats? Will their reputation be softened by this news? I lived for a number of years in a city fondly known as “Allston Rat City” nicknamed for its truly giant rats. On my street, rats were routinely run over, progressively flattened by cars until they became one with the road. It’s a cool party story I like to pull out. Everyone who has lived in Allston has at least two rat stories. I’ll spare you the second one.

The Plague is Back!

Actually, it never left. At least not in Madagascar, where plague is endemic, and is reported every year in the area. In fact, they even have a plague season. It runs from September through April, and they usually get about 400 cases each year. However, according the WHO “the ongoing pneumonic plague event has been reported in a non-endemic area and in densely populated cities for the first time.”  There have already been more then 300 cases and 40 deaths in Madagascar and plague season is just getting started.

Usually, bubonic plague is the more common form in this area, and is transmitted via fleas. Pneumonic plague, which effects the lungs, is airborne, and is therefore more easily spread and more deadly. If left untreated, bubonic plague travels to the lungs and becomes pneumonic plague. Without antibiotics, pneumonic plague is 100% fatal. The WHO is working on distributing more antibiotics, but for a disease that’s spread via the air and has reached a densely populated area, they are facing a complicated race against time.

WHO Plague Fact Sheet

“The black death is alive and well in the American Southwest”

Or at least that’s what the news would like you to believe in their alarmist articles. The plague! Fleas! (Fleas are legitimately terrifying I admit.)

“Symptoms of plague in humans generally appear within two to six days following exposure and include the following: fever, chills, headache, weakness, muscle pain, and swollen lymph glands (called ‘buboes’) in the groin, armpits or limbs. The disease can become septicemic (spreading throughout the bloodstream) and/or pneumonic (affecting the lungs), but is curable with proper antibiotic therapy if diagnosed and treated early.”

I know, I know, put the “the plague” in an article headline and you get clicks. And yes, it can be fatal. But the above quote should be more heavily emphasized, as many people will read the headline and nothing else. Seriously, one headline reads:  “Black Death hits AMERICA as the medieval plague that wiped out a quarter of the world’s population is found in FLEAS in Arizona.” This is accurate but melodramatic, as a similar death toll is unlikely to happen today.

On the other hand, I could be wrong! Who knows! Everything is a gamble. Enjoy this giant picture of a flea. Pro tip: Don’t go out of your way to search for flea or plague pictures.