Plague

Plague is an infectious disease caused by the bacterium Yersinia pestis, transmitted to humans mainly through the bite of infected fleas that have fed on rodents. It occurs in three principal forms: bubonic plague, marked by painful swollen lymph nodes called buboes; septicemic plague, in which the infection spreads through the bloodstream; and pneumonic plague, which infects the lungs and can spread directly between people through respiratory droplets. Left untreated, plague has a high fatality rate, and it was responsible for historic pandemics including the Black Death of the fourteenth century, which killed a large share of Europe population. Modern cases are treated with antibiotics and remain rare but ongoing in parts of Africa, Asia and the Americas.