Buboic plague dna has been found in the teeth of victims. They seem to center their ideas on rats spreading the disease but it was fleas that did the biting.
There is evidence that it was caused by a bacterium. There is no evidence it was a virus.
The mass extermination of “witches’ familiars” [aka cats and to a lesser extent, dogs] let the rats flourish.
More rats = more fleas.
Hysteria has teetering on the verge of a new Burning Time.