Yet another paper discovers the obvious. The "cure" for the plague was 40 days off isolation of affected homes or cities. Rats and fleas don't respect human quarantines.
Another factor is rats. They are killed by plague just like humans. At least one person should have noted large volumes of rats dropping dead everywhere, but that isn't mentioned in writings of the time.
"But feral cats won’t stray three blocks beyond where they were born, and few mice will venture more than a hundred feet from their burrows in a lifetime."
If rats don't travel, then how do they spread the plague? If they do travel, then quarantine would not work. If they travel with humans, then we would expect to see massively higher infection and death rates among travellers due to prolonged times with infected rats as they dragged them everywhere (where is this evidence?) The plague spread across Europe at an enormously fast rate (some believe that hemorrhagic fever with a separate bubonic outbreak in Italy).
Another factor is rats. They are killed by plague just like humans. At least one person should have noted large volumes of rats dropping dead everywhere, but that isn't mentioned in writings of the time.