3.3.1: The Black Death
A bacterial infection caused the infamous pandemics known as the bubonic and pneumonic plagues throughout Europe, Asia, Russia, India, and the Middle East from the 14th to 20th centuries. The bacteria that caused the bubonic version first infected fleas, which were carried on rats (this type of transmission is called vector-borne transmission - the flea is the vector, the rats are the reservoir). Victims developed “buboes” or swelling of the lymph nodes, as the bacteria tended to proliferate there. Another type of bubonic plague caused gangrene of the extremities. The pneumonic version infected the respiratory tract and was spread between humans via breathing, coughing, or sneezing. All types of this disease were initiated with a fever and flu-like symptoms, then rapidly progressed over the course of a few to several days. Before antibiotics were made available in the early 20th century, this disease was quite deadly - killing an estimated 25-50 million people in Europe and half of the population of China between the 12th and 15th centuries (Tulchinsky & Varavikova, 2014, Glatter & Finkelman, 2021).
Responses to the black plague were characterized by fear and superstition. Cats were suspected of carrying the disease, which led to their extermination. Oddly enough, the cat population could have helped cull the rats that actually carried the infected fleas (Tulchinsky & Varavikova, 2014). Nowadays we know that cats are also susceptible to the plague as well, from eating infected rats or being bitten by fleas (CDC, 2022). Another, potentially more effective strategy involved quarantining ships for 30-40 days in port before allowing any goods or people to disembark. (The word “quarantine” actually derives from this practice - in Italian, quarantina = 40 days. ) Additionally, social distancing measures were attempted by some governments with the ban on religious functions or funerals, but these measures were often resisted heavily by the public (Tulchinsky & Varavikova, 2014).
Jewish communities seemed to have lower rates of infection from the bubonic plague, the recognition of which stoked anti-semitism among the Christian Europeans. Jews were blamed for spreading the plague, persecuted, and massacred throughout Europe as a result of this superstition. Although Hebraic hygiene practices could have played a role in reducing the spread of plague in these communities, it was later discovered that a genetic mutation caused by a rare disease (familial Mediterranean fever), provides immunity to the plague bacteria. This genetic mutation is found most often in people of Israeli, Armenian, Arab, and Turkish descent (Glatter & Finkelman, 2021).
Although we may think of the plague as a long-past historical disease, it is still endemic (recurring seasonally) in several parts of the world. It can be treated if caught early with antibiotics, and those exposed can also use antibiotics as a prophylactic (preventative) measure. However, there is still some concern about the pneumonic plague being used for bioterrorism, as it causes such swift illness and death, and can be transmitted easily between humans (Ansari et al., 2020).