The bubonic plague was allegedly caused by a bacterium called “Yersina pestis”, which was often found on wild rodents in large quantities and densities. At the time, these “wild rodents” were mostly black rats that were found on ships that were used for trade. If a rat was a host to a flea carrying the deadly bacterium, the rat would most likely die within 14 days. In order to survive, the fleas would then turn to human hosts. This is how the plague spread. Once the bacterium was present, the disease took three to five days to develop. In 80% of cases, the human host would die within another three to five days. Interestingly enough, it took quite a while for people to realize that an epidemic was breaking through. For example, in small towns
