Rats were likely not the culprits, rather it was lice spreading from human to human.

https://www.bbc.com/news/science-environment-42690577

> "The conclusion was very clear," said Prof Stenseth. "The lice model fits best."

> "It would be unlikely to spread as fast as it did if it was transmitted by rats.

> "It would have to go through this extra loop of the rats, rather than being spread from person to person."

I remember the 3.5 scandal that created Pathfinder. Heard WotC doing the same now with 5e?