What is it?
Bubonic plague was responsible for many pandemics throughout human history, and each time it absolutely destroyed the human populations it affected.
Bubonic plague is caused by the bacterium Yersinia pestis. It gets inside a person when they are bitten by an infected rat flea. Therefore plague could appear anywhere there are rats, and unfortunately, rats exist almost across the entire world and they spread very easily. Rats were instrumental in spreading bubonic plague, and would often catch rides on ships to do so. Bubonic plague starts with flu-like symptoms such as fever, headaches, vomiting, but also inflamed lymph nodes. “Buboes” are swollen lymph nodes that may break open, spilling bacteria infected pus everywhere!
The Plague of Justinian in the 500’s was the first plague pandemic and it killed off half the population of western Europe! It had profound social, economic, and political effects across Europe and the Near East. The second pandemic, starting in the 1300’s, was known as The Black Death. You may have heard about it before, as it is pretty infamous due to being the most fatal pandemic in history! It spread largely due to increased trade along the Silk Road throughout Europe. The third pandemic is known as “the modern pandemic” since it started in the mid-19th century and continued until 1959, spreading throughout the world from China. Nowadays, plague can be found scattered throughout rural United States in various rodent species (Miksanek, 2007; World Health Organization, n. d.).
How did we fight it?
Quarantine
Plague was notoriously difficult to control, and we did not have many means to fight it. Quarantine – isolating those infected – was essentially invented because of the bubonic plague. Despite not knowing how the disease spread, there was a recognition that association with infected individuals often resulted in spread of the disease as far back as the 100’s (Miksanek, 2007).
Fun fact! – “quarantine” comes from the Italian words quaranto giorni and refers to the 40-day period in which ships were required to remain in isolation upon arrival to a port.
While individuals on ships would isolate in ports, often resulting in 90% of the ship’s population dying from the disease, the most important set of individuals would not isolate – rats! Rats do not respect any man-made limitations, and since they carried the plague-infected fleas, it was easy for the rats to make it into the city and spread bubonic plague (Miksanek, 2007).
Sometimes cities would impose household quarantines. The city would require any households with infected individuals to completely shut their doors. The uninfected would then become infected from plague-infested rats, and these rats would come and go from the house, too. Thus, it did not result in lower infection rates but instead higher mortality (Miksanek, 2007).
Current Day
In the present day, there is little concern for a plague pandemic to ever occur. Biological warfare remains a risk, however. Plague can be turned into a mist form and released as an aerosol, with even just a few bacteria being sufficient to infect people.
If a bubonic plague outbreak ever occurred, we now have antibiotics which can reduce fatality significantly. The normal fatality rate of bubonic plague is 66%; when treated with antibiotics, this reduces to just 13% (Nelson et al., 2021).
Vaccines?
A vaccine to combat plague does exist. Simply called the plague vaccine, the earliest versions contained inactivated Yersinia pestis bacteria but were not that effective against pneumonic plague. And so recombinant protein vaccines and live, attenuated vaccines were developed. The way attenuated vaccines work is by decreasing the ability of the pathogen to cause severe reactions in people, and injecting the person with the weaker disease. So an attenuated plague vaccine literally has plague bacteria in it, but they are really weak versions (Bubeck & Dube, 2007). The other vaccine, recombinant protein, contains pieces of the bacteria that the immune system can use to store as memory (Gavi, the Vaccine Alliance, n.d.). While not commonly given out because of low cases numbers world-wide nowadays, plague vaccines could be vital to battle any future bio-terrorism attacks that use plague to infect people (Williamson & Oyston, 2017).
References
Bubeck, S. S., & Dube, P. H. (2007). Yersinia pestis CO92ΔyopH Is a Potent Live, Attenuated Plague Vaccine. Clinical and Vaccine Immunology : CVI, 14(9), 1235. https://doi.org/10.1128/CVI.00137-07
Gavi, the Vaccine Alliance. (n.d.). Retrieved August 29, 2023, from https://www.gavi.org/vaccineswork/what-are-protein-subunit-vaccines-and-how-could-they-be-used-against-covid-19
Miksanek, T. (2007). Twelve Diseases That Changed Our World. JAMA: The Journal of the American Medical Association, 298(24), 2914–2920.
Nelson, C., Meaney-Delman, D., Fleck-Derderian, S., Cooley, K., Yu, P., & Mead, P. (2021). Antimicrobial Treatment and Prophylaxis of Plague: Recommendations for Naturally Acquired Infections and Bioterrorism Response. MMWR. Recommendations and Reports. 70(3), 1-32.
Williamson, E. D., & Oyston, P. C. F. (2017). Plague Vaccines. Plotkin’s Vaccines, 762-772.e4. https://doi.org/10.1016/B978-0-323-35761-6.00044-4
World Health Organization. (n.d.). Plague. World Health Organization. https://www.who.int/en/news-room/fact-sheets/detail/plague