Better hygiene, better sanitation, and slum clearances. Turns out you're much less likely to catch a bacterial infection if you keep yourself clean, don't shit where you eat, and don't live cheek by jowel with thirty people in a single hovel.
Killed everyone susceptible too.
There’s a fun theory that the Black Death wasn’t a bacterium at all, but repeated waves of an haemorrhagic fever. The evidence put forward to support this is quite interesting. There were none of the type of rats that carry the fleas for example in Iceland, yet they got hit hard, even away from the docks where a few rats might disembark. The pattern of spread is traceable through parish death records and it seems to indicate an incubation period of a few weeks. And people at the time knew it spread person to person - and that gives a few hints it wasn’t a bacterium spread by fleas.
Bubonic plague is the main form, and it’s really only easily transmissible person to person through very close nursing or when it turns into pneumonic plague. Nobody is walking around with pneumonic plague. So then you have known documented cases like Eyam in Derbyshire:
- small village. Plague free.
-tailor arrives in town, only outsider arriving
-dies of plague
-plague outbreak begins.
So how does this happen? Fleas in the cloth is the accepted one but that makes no sense either. He was clearly Infected with something on arrival. Eyam is famous for Th e villagers enforcing their own quarantines - they stopped anyone leaving or coming in and you can still see the plague stones where they left money for people who brought food, in a hollow filled with vinegar.
But hang on:
-they knew it was spread by close contact. They knew vinegar on the money cleaned it.
-they realised a distance stopped the spread (there were stories of lovers meeting at opposite sides of a dell.) But the idea that the fleas were infected then infected the local rats doesn’t hold up. Rats don’t care about a ten metre distance, they will spread throughout a terrace or village. But the spread is only within households and documented contacts, it’s person to person, you can literally trace it through the death records, and that wouldn’t happen if it was rats and fleas. Quarantine worked. That wouldn’t happen if it was rats, rats go next door. It has a clearly defined incubation that doesn’t match y pestis. It can’t be pneumonic plague, once you’re in that state you’re a dead person and not walking around. It very clearly had a non symptomatic incubation stage where it was transmissible (the word quarantine comes from this and was forty days of isolation applied to the ships.)
Waves of plague happened, and then it just disappeared, and nobody really knows why. Y pestis does NOT fit the way it spread,
It’s possible it was an ancient version if y pestis of course, and it was knocking around at the time and it did cause outbreaks, but I personally am not convinced it was responsible for that amount of death. Something like CCHF (Crimean Congo haemorrhagic fever) fits the bill pretty well, possibly introduced from the levant and echoing around Europe for a while.