If the disease spread to the lung through the blood, it caused an invariably fatal pneumonia, pneumonic plague, and in that form plague was directly transmissible from person to person. When bacteraemia followed, it caused haemorrhaging and necrosis of the skin rapidly followed by septicaemic shock and death, septicaemic plague. boubon = ‘swelling in the groin’), this was bubonic plague. In most human plague epidemics, infection initially took the form of large purulent abscesses of lymph nodes, the bubo (L. On more than one occasion plague irrevocably changed the social and economic fabric of society. There have been three great world pandemics of plague recorded, in 541, 1347, and 1894 CE, each time causing devastating mortality of people and animals across nations and continents.

Bubonic plague also has military significance and is listed by the Centers for Disease Control and Prevention as a Category A bioterrorism agent.1 Yersinia pestis is a very pathogenic organism to both humans and animals and before antibiotics had a very high mortality rate. Plague is also transmissible person to person when in its pneumonic form.

The primary hosts of the fleas are the black urban rat and the brown sewer rat. In epidemics plague is transmitted to humans by the bite of the Oriental or Indian rat flea and the human flea. Plague is an acute infectious disease caused by the bacillus Yersinia pestis and is still endemic in indigenous rodent populations of South and North America, Africa and Central Asia.

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