Since we are just finishing the pandemic of a century, it behooves us to look back at the Second Plague, also called the Black Death, in Eurasia using the recent advances in the science of genomics. The analysis of the DNA from the bones of more than 500 bodies of those who died before, during, and after the Black Death in London and Denmark found that people with two copies of the gene variant ERAP2 which produces a full size protein were twice as likely to survive as those who had two copies of the variant which produced a truncated version. This comes from Science Magazine which made this one of the 10 breakthroughs of 2022.
The protein helps immune cells recognize and fight threatening viruses. This bubonic plague was the infection by a bacteria Yersinia Pestis, named after Dr. Alexandre Yersin who discovered it. The protein is called endoplasmic reticulum aminopeptidate 2, and is a cytokine which stimulates the immune system to fight the bacteria.
45% of British people still have this protective gene variant, but it also comes with a risk of developing autoimmune diseases, such as rheumatoid arthritis and inflammatory bowel disease. However, it also protects against bubonic plagues, pneumonia, and COVID-19.
This is a good point to note that Y. Pestis is easily treated by antibiotics today, and is rare.
There is still debate on the geographical origin and method of transmission of the plague. It is attributed to be carried by fleas from rodents. The fleas get infected by the bacteria and have to suck up blood, so they attack humans. However, the rapid spread of the disease is also attributed to human fleas, and also to spreading like pneumonia since it infects the lungs. Once infected, the victim died in two to seven days.
Below is the map of the spread of the disease, from 1346 to 1353, from Wikipedia. The disease is estimated to have killed 30% to 50% or 60% of Europeans, or from 75 million to 200 million people. The map source is:
https://commons.wikimedia.org/wiki/File:1346-1353_spread_of_the_Black_Death_in_Europe_map.svg
The supposed origin of the European infection was in the Crimea at the port of Feodosia (in light green), also previously called Kaffa, on the Black Sea. The infection was spread from rats on ships. However, analysis this year from an unusual number of bodies from deaths in 1338-9 due to pestilence in the northeastern part of Kyrgyzstan in the Tian-Shan region, show an earlier occurrence of Y. Pestis. This is next to the region of China currently occupied by the Muslim Uighurs. From the map, you can see the uncanny match of the boundary of the Golden Horde of Mongols to the current invasion of Ukraine by Russia. The port of Kaffa had been bought from the Golden Horde by the Genoese shippers.
The First Plague was the Plague of Justinian from 541 to 549 AD, which was also caused by a different strain of Y. Pestis. It also spread throughout Europe and the Middle East. In Constantinople, the capitol of the Byzantine empire, it caused the death of 20-40% of the population. Emperor Justinian I was infected by it but recovered. Perhaps 15-100 million died of it over two centuries of its recurrence, or 25-60% of the European population when it started. Lower figures are also argued for.
We see the use of modern science and realistic governments in defeating the Covid pandemic in three years with at most 20 million deaths in a much more populated and rapidly connected world. Obviously, we need much more study of the Black Death to determine what segments of the population survived and why, and why subsequent infections of it were less deadly.
