WORLD HISTORY

Detailed explanation-1: -Plague, caused by the bacterium Yersinia pestis, can spread through human populations by multiple transmission pathways. Today, most human plague cases are bubonic, caused by spillover of infected fleas from rodent epizootics, or pneumonic, caused by inhalation of infectious droplets.

Detailed explanation-2: -Rats have long been blamed for spreading the parasites that transmitted plague throughout medieval Europe and Asia, killing millions of people.

Detailed explanation-3: -Black rats were the most common at this time, and carried the bacteria called Yersinia pestis, which caused the plague. The rats then spread it to fleas that lived on their bodies. The fleas would drink the blood of infected rats, swallowing harmful bacteria. They then passed the infection onto humans by biting them.

Detailed explanation-4: -Bubonic plague is transmitted through the bite of an infected flea or exposure to infected material through a break in the skin. Symptoms include swollen, tender lymph glands called buboes.