As we have all learned in high school, rats cause outbreaks of the Black Plague. The plague lives in fleas, which live on rats, and when those fleas jump to humans and bite them, you’ve got plague. This is so well accepted that we currently blame prairie dogs for plague outbreaks. But the rodents may be off the hook. Scientists at the University of Oslo have used complex simulations to test out the spread of the plague, and it turns out rats and other rodents may not be what caused the worst disease outbreak in human history.
It wasn’t fleas on rats, it turns out, that made humans sick. It was fleas and lice on humans that made us sick.
It’s worth remembering that until extremely recently, our collective skin was crawling with parasites. Bedbugs are in the historical record going back centuries, and the same is true of a lot of other pests like fleas and lice. It wasn’t until modern sanitation, the invention of easier-to-launder clothes, and realizing that bathing regularly was a good idea for reasons beyond stench, that we really started winning the war against the disgusting little monsters.
That made researchers at the University of Oslo curious. Keep in mind, the Black Death is well-documented in the Middle Ages, at least by historical standards, and we have a pretty good idea of where outbreaks started and how they spread. So, they designed three models to simulate the plague: Airborne transmission, rat based transmission, and human-based transmission. Then, they put the computer to work to see what matched the historical record in nine cities. It turns out, the human-based model of transmission matched the records best in seven of nine cities.
So, yeah, the plague spread because we were gross and covered in pests, not because of the vermin. Not that this is a case for more vermin.
This means without intending to, we’ve figured out a way to limit diseases that spread by lice and fleas. Keep in mind, regular bathing and laundry limits the ability of most vermin to settle into our bodies. So a plague as terrible as the Black Death is a lot more unlikely, at least by this particular vector. Although we really can’t emphasize enough the stench thing is also a good reason to bathe regularly.