The Black Death was a pandemic of the Bubonic plague that swept through Asia and Europe from 1346 to 1351, killing an estimated 200 million people.
The disease was caused by the bacteria called Yersinia pestis, living in the intestines of fleas in black rats and other rodents. These rodents fled areas in Asia that were becoming drier because of climate change and they brought their fleas to human settlements where the bacteria began to infect humans.
The plague entered Europe several ways, but the main transmission, according to scholars, is when Mongol leader Jani Beg threw corpses over the wall of Kaffa, a port city he was besieging. Beg’s men were already dying of the plague so he threw corpses of his men into the city and the disease spread.
Genoese and Venetian traders left Kaffa in their ships and took the disease with them to the rest of Europe.
From Genoa and Venice the disease spread to the rest of Italy. From Italy it would spread to the rest of Europe, even crossing the English Channel to reach London in 1348.
Rodents with infected fleas also came on merchant ships traveling from Asia to Europe on the Silk Road.
The Black Plague also spread in the Middle East. The Mongols had already spread it throughout China on their way to Kaffa. It also reached Russia. By 1347 it was already in Alexandria, from there it was brought to Gaza, Lebanon, Syria, Palestine, Accra, Jerusalem, and even Mecca.
Since the disease spread quickly in thickly-populated areas, it slowed down as it got to less-populated areas. Measures like quarantine also helped slow the spread of the disease among people.
A pandemic is a disease covering a huge area. While an epidemic only affects a community, a pandemic can affect an entire country or even an entire region in the world.
A bite from a flea could transmit the bacteria to humans. From there human-to-human infection occurred when an uninfected person was exposed to the infected tissue or the cough of someone with the disease.
The Silk Road was a network of trade routes over land and sea that allowed merchants to move their good between Asia and Europe. It got the name because silk from China made up majority of the trade items from east to west.
People infected with the Bubonic Plague had blackish lumps called buboes appear in the neck, groin, or armpits. These buboes oozed pus and bled when broken.
This was followed by fever and vomiting of blood. The victim would usually be dead within two to seven days after being infected.