People back then lacked general hygiene, which is understandable since, there was no indoor pluming at the time. The plague was caused by rats who carried fleas, but I think people caused the spread, not the rats with fleas. People carried the plague through trade routes, unknowingly. People could of just kept to themselves during this time, stay away from open wounds, clothes were also infected as well as, towns. If towns were contaminated, no one should be able to leave, just incase if they do have the disease, they don't spread it.
