Bubonic plague risk factors
Those people who lived in the middle ages were at extremely high risk due to the contagious nature of the disease. Also, there were many rats living close to the people who were infected with the bubonic plague. Rats are one of many rodents that can be a carrier for Yersinia pestis or the bubonic plague.
Who is at highest risk?
People can get the plague when they are bitten by a flea that carries the plague bacteria from an infected rodent. In rare cases, you may get the disease when handling an infected animal. Risk factors for plague include a recent flea bite and exposure to rodents, especially rabbits, squirrels, or prairie dogs, or scratches or bites from infected domestic cats.