The historian Procopius wrote, in Volume II of History of the Wars, of his personal encounter with the plague and the effect it had on the rising empire. In the spring of 542, the plague arrived in Constantinople, working its way from port city to port city and spreading around the Mediterranean Sea, later migrating inland eastward into Asia Minor and west into Greece and Italy. The Plague of Justinian is said to have been "completed" in the middle of the 8th century. Because the infectious disease spread inland by the transferring of merchandise through Justinians efforts in acquiring luxurious goods of the time and exporting supplies, his capital became the leading exporter of the bubonic plague. Procopius, in his work Secret History, declared that Justinian was a demon of an emperor who either created the plague himself or was being punished for his sinfulness. Second pandemic
In the Late Middle Ages Europe experienced the deadliest disease outbreak in history when the Black Death, the infamous pandemic of bubonic plague, hit in 1347, killing one-third of the European human population. Some historians believe that society subsequently became more violent as the mass mortality rate cheapened life and thus increased warfare, crime, popular revolt, waves of flagellants, and persecution. The Black Death originated in Central Asia and spread from Italy and then throughout other European countries. Arab historians Ibn Al-Wardni and Almaqrizi believed the Black Death originated in Mongolia.
The flea is parasitic on house and field rats and seeks out other prey when its rodent hosts die. Rats were an amplifying factor to bubonic plague due to their common association with humans as well as the nature of their blood. The rats blood allowed the rat to withstand a major concentration of the plague. The bacteria form aggregates in the gut of infected fleas and this results in the flea regurgitating ingested blood, which is now infected, into the bite site of a rodent or human host. Once established, bacteria rapidly spread to the lymph nodes and multiply. The fleas that transmit the disease only directly infect humans when the rat population in the area is wiped out from a mass infection. Furthermore, in areas of a large population of rats, the animals can harbor low levels of the plague infection without causing human outbreaks. With no new rat inputs being added to the population from other areas, the infection would only spread to humans in very rare cases of overcrowding. Signs and symptoms
After being transmitted via the bite of an infected flea, the Y. pestis bacteria become localized in an inflamed lymph node, where they begin to colonize and reproduce. Infected lymph nodes develop hemorrhages, which result in the death of tissue.Y. pestis bacilli can resist phagocytosis and even reproduce inside phagocytes and kill them. As the disease progresses, the lymph nodes can hemorrhage and become swollen and necrotic. Bubonic plague can progress to lethal septicemic plague in some cases.