Yersinia pestis In 541 A.D., a plague known as the Plague of Justinian named after the Byzantine emperor is the first Black Plague. This plague wiped out millions of people throughout Eastern Roman/Byzantine region, which is called Istanbul today. Then between 1347 and 1351 the well-known Black Plague, also called the Black Death, is the most devastating pandemic in our history. It was estimated that tens of millions of people dies in Europe during this time. It is said that the cause of both plagues was linked to Yersinia pestis. But was it the same strain or not? Yersinia pestis is a facultative anaerobic bacterium that infects humans and animals. Yersinia pestis mainly infects rats and other rodents which are the prime source for the bacteria. Fleas are the prime vectors carrying the bacteria from one species to another. The fleas bite rodents infected with Yersinia pestis and then the fleas bite people and the disease is transmitted. In recent years scientists have been able to confirm that the Plague of Justinian and the Black Death were indeed caused by Yersinia pestis. To find out if the strains matched, scientists were able to extract DNA from those that were victims of both plagues. By digging up the victims and using the DNA found in their teeth it was determined that it was two spate strains. Now the question becomes, can this pandemic occur again? Even though scientists believe this bacterium is more than capable of causing a reoccurrence in this