Plague: The Black Death

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Plague can be a very severe disease in people, with a case-fatality ratio of 30%-60% if left untreated.It was known as the "Black Death" during the fourteenth century, causing an estimated 50 million deaths.Plague is caused by the bacteria Yersinia Pestis, a zoonotic bacteria, usually found in small animals and their fleas.People infected with plague usually develop “flu-like” symptoms after an incubation period of 3-7 days.There are 3 forms of plague infection depending on the route of infection: bubonic, septicaemic and pneumonic. Bubonic-characterized by painful swollen lymph nodes or ‘buboes’- is the most common form.Plague epidemics have occurred in Africa, Asia, and South America but since the 1990s, most human cases have occurred in