Erm
I actually read some pretty convincing evidence in New Scientist a couple of years ago that pointed out a few facts about Bubonic plague.
The main one being that the black death spread far too quickly to be Bubonic plague and was far more likely to be a very virulent form of Ebola.
The symptoms are similar in lots of ways but an airbourne Ebola could travel upto 70 miles in less than a day and infect a seemingly safe household, killing all the occupants within a very short time period.
there are many accounts of villages mysteriously falling ill and dying even when there had been no visitors and they were too far away to have gotten Rats from elsewhere.
Bubonic plague is only passed from flea to human by physical contact so couldnt possibly have gotten that far in such a short period of time.
I don't remember the details but the black death was killing people within 2 or 3 days where the bubonic and pneumonic plague have something like a week gestation period.
Zygo