The Black Death"No plague had ever been so fatal, or so horrible. Blood was its Avatar and its seal: the redness and horror of blood. " (Edgar Allen Poe The Masque of the Red Death.) Many thought the Black Death was a curse from God; punishment for the sins committed by the infected. Those who survived were the chosen people, those who respected the laws of the Church. Scientists now know that the devastating disease was not the result of sin or spiritual inadequacy, but that the terrible disease was caused by a strain of bacteria called Yersinia pestis. The bacteria were carried by fleas on rats, which were quite abundant in medieval cities due to unsanitary conditions and overpopulation. The fleas would bite the rats and become infected with the diseased blood. The fleas would then jump from rats to people, thus infecting the host. Because the plague spread easily, through sneezing, coughing, and fleas, the infection spread like wildfire. At the end of 1300 over a third of the populations of Europe, Asia and Africa were completely annihilated. The Black Death was by far the deadliest disease ever known to man. It spread and killed with such virulence that the course of human history changed forever. Little known to the average person, there were three forms of the Death Star. They were all caused by the same bacteria, but each had very different symptoms. The three forms, while not as deadly, brutally killed millions of people during the Middle Ages. The most common and well-known strain of the Black Death was bubonic plague. Victims were prone to swollen and inflamed lymph nodes, a feature known as a bubo, hence the name bubonic plague. The lymph nodes would swell to enormous capacities and eventually burst. Other symptoms included headache, nausea, joint pain, high fever and vomiting. Symptoms usually took about a week to appear and the mortality rate was around 30-75%. The second form of the Black Death was pneumonic plague. It was the second most commonly observed form of the disease, although it was not as widespread as the bubonic plague. Many of the victims died before they could infect others. This form of plague attacked the lungs. Slimy blood-tinged mucus was emitted from the mouth and as the disease progressed the sputum became fluid and bright red in colour..