Epidemics of plague past, present, and future

Plague has a deservedly bad reputation. The disease killed over 20 million people in India during the early 1900s, and even more people during the so-called Black Death that swept Europe beginning in 1346. The causative agent, Yersinia pestis, circulates on five continents, infecting a range of animal reservoirs living in diverse ecological settings. Human disease is typically acquired through flea bites and takes the form of bubonic plague; however, infection can also spread to the lungs, producing pneumonic infection.