Once again, people who don't get their fact straight are confusing the issue.
The Plague (Yersenia Pestis) is spread by fleas on rats. This is a well known and scientific fact. However, it can also be spread by airbourne particle if the infection moves from the lymph nodes (bubos or swollen lumps in the arm pits and groin is where the name bubonic plague comes from) to the lungs.
Pneumonic Plague (Yersenia Pestis in the lung) is extremely contagious and universally fatal. The last I looked, there are no known survivors, even with today's medical care and treatment with antibiotics.
So it is no wonder that in the town that once a person developed pneumonia from the plague, it spread extremely quickly and they all died. The initial infection was brought in by rats, but it may then have spread person to person as you would see if you RTFA.