The History of Plague - Part 1. The Three Great Pandemics

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. In epidemics plague is transmitted to humans by the bite of the Oriental or Indian rat flea and the human flea. The primary hosts of the fleas are the black urban rat and the brown sewer rat. Plague is also transmissible person to person when in its pneumonic form. Yersinia pestis is a very pathogenic organism to both humans and animals and before antibiotics had a very high mortality rate. Bubonic plague also has military significance and is listed by the Centers for Disease Control and Prevention as a Category A bioterrorism agent.