What is plague? What is the history of plague?

Plague is a bacterial disease that is infamous for causing millions of deaths due to a pandemic (widespread epidemic) during the Middle Ages in Europe, peaking in the 14th century. Many historical references describe the illness, which has been referred to as the Black Death or a "pestilence in the air." The first reported plague pandemic began in 541 A.D. and lasted for over 200 years, killing an estimated 100 million people or more throughout the Mediterranean basin. The so-called Black Death, or pandemic of the Middle Ages, began in China and made its way to Europe, causing the death of 60% of the entire population. The third, or modern, pandemic started in China in the 19th century and spread to many parts of the world in port cities. More recently, the World Health Organization reported an outbreak of plague in Madagascar in November 2014 and again from August through October 30, 2017, with a total of 1,801 confirmed, probable, and suspected cases of plague, including 127 deaths according to Madagascar health officials.

Rodents and many other kinds of animals can be infected with plague-causing bacteria. People contract the bacteria through bites of fleas that have fed on plague-infected rodents. Humans can also develop the infection from handling fluids or tissues from infected animals. People with pneumonic plague can also transmit the infection to other humans via coughing infectious droplets into the air.