The Black Death was one of the most devastating pandemics in human history, resulting in the deaths of an estimated 75 to 200 million people in Eurasia and peaking in Europe in the years 1346–1353. It killed between 30-60% of Europe's population.
The Black Death is thought to have originated in the arid plains of Central Asia, where it then traveled along the Silk Road, reaching Crimea by 1343. From there it likely carried by Oriental rat fleas living on the black rats that were regular passengers on merchant ships. Spreading throughout the Mediterranean and Europe.
The plague disease, caused by Yersinia pestis, is enzymatic in populations of fleas carried by ground rodents, including marmots, in various areas including Central Asia, Kurdistan, Western Asia, Northern India and Uganda. The fleas went on to the rats and then started to jump on the humans and bite them which made them get the disease.
In the middle of the 14th century, however, there seemed to be no rational explanation for it. No one knew exactly how the Black Death was transmitted from one patient to another according to one doctor, for example, “instantaneous death occurs when the aerial spirit escaping from the eyes of the sick man strikes the healthy person standing near and looking at the sick” and no one knew how to prevent or treat it.
People did not understand the biology of the disease so most people believed that the Black Death was a kind of divine punishment or retribution for sins against God such as greed, blasphemy, heresy, fornication and worldliness. So they thought to make the plague stop was to win over God's forgiveness. Some people believed that the way to do this was to purge their communities of heretics and other troublemakers so many thousands of Jews were massacred in 1348 and 1349.
With the terror and uncertainty of the Black Death epidemic people began lashing out at their neighbors others coped by turning inward and fretting about the condition of their own souls. Some upper-class men joined processions of flagellants that traveled from town to town and engaged in public displays of penance and punishment: They would beat themselves and one another with heavy leather straps studded with sharp pieces of metal while the townspeople looked on.
For 33 1/2 days, the flagellants repeated this ritual three times a day. Then they would move on to the next town and begin the process over again. Though the flagellant movement did provide some comfort to people who felt powerless in the face of inexplicable tragedy, it soon began to worry the Pope, whose authority the flagellants had begun to usurp. In the face of this papal resistance, the movement disintegrated.
In Black death, the most common form, bacteria infect the lymph system and become inflamed. The lymph or lymphatic system is a major component of your body's immune system. The organs within the lymphatic system are the tonsils, adenoids, spleen, and thymus. You get the black death from the bite of an infected flea or rodent. In rare cases, bacteria, from a piece of contaminated clothing or other material used by a person with plague, enter the body through an opening in the skin.
The Black death affects the lymph nodes. Within 3 to 7 days of exposure to plague bacteria, you will develop flu-like symptoms such as fever, headache, chills, weakness, and swollen, tender lymph glands. It also is makes you have abdominal pain, shock, and bleeding underneath the skin or other organs. Buboes, however, do not develop. It can not be spread to person to person.
Resulting in the deaths of an estimated 75 to 200 million people in Eurasia and peaking in Europe. The Black Death is estimated to have killed 30–60% of Europe's total population. In total, the plague may have reduced the world population from an estimated 450 million down to 350–375 million in the 14th century. The world population as a whole did not recover to previous plague levels until the 17th century.