The bubonic plague: why it is no longer a threat to humanity

Authored by Jennifer Anstey

Engraving of a plague doctor in seventeenth-century Rome, c. 1656 [1]


Reports emerged a few weeks ago of a case of the bubonic plague in the Inner Mongolia region of China, quickly resulting in mass panic as the infamous disease has caused millions of losses of life historically. Cases do appear yearly but, due to advances in medicine and understanding of transmission, the disease no longer poses an immediate threat to humanity.[2]

The bubonic plague is one of the three basic kinds of plague, and is caused by the enterobacteria ‘Yersinia pestis’.[3] Enterobacteria are known to cause intestinal upset and are often found in areas of low hygiene and poor water decontamination as a result of their preference for anaerobic (low / no oxygen) environments.[4] The recent case diagnosed is non-transmissible between humans and is not yet determined to be a major outbreak, although there have been 14 reported outbreaks since 2001.[2,5] Many Marmots are known to be infected with the disease, so it is recommended that these animals are not consumed or approached; however, the bacterium can reside elsewhere and occurrences are seen in places such as the US each year.[2] Places in the US where the plague has been seen most frequently include New Mexico, Northern Arizona, southern Colorado, California, southern Oregon and western Nevada.[6] Bubonic plague is often transmitted initially by flea bites- this differs from pneumonic plague, for example, by virtue of transmission pathway.[5] Pneumonic plague is transmitted by droplets from another human and has a relatively short incubation period of 24 hours or longer and may be fatal if not treated within 24 hours of symptoms beginning to show.[7]

Modern treatment methods are the reason we no longer need to worry about a pandemic that previously killed 2/3 of the population of Europe. The black death (1347 -1351) had a death rate ranging from 60-90%, something that is widely taught in the early years of school. The now-familiar practice of isolation was widely used as well as greater trades restrictions, however, the limited knowledge of disease and existence of bacteria led to an array of ineffective treatments.[8] These treatments included bloodletting, consumption of arsenic or mercury, flowers held to the nose and flagellation amongst others.[9] In the modern day, we now know that if antibiotics, such as Streptomycin and Gentamicin, are administered within 24 hours the outcome will usually not be fatal. Streptomycin typically acts by binding to a ribosomal subunit of organisms, thus interfering with and preventing protein synthesis (initiation and elongation).[10] In the incidence of a large-scale plague outbreak, oral doxycycline and ciprofloxacin are instead used.[5] Additionally, there are vaccines available worldwide with both live attenuated (have antigens but are not able to reproduce) and formalin-killed (pathogen inactivated by the formalin chemical) forms of the bacterium; however, a month or so is required to ‘form a protective immune response’ according to the WHO.[11-13]

The panic surrounding the news is likely due to a mixture of misinformation and the current climate around disease caused by the coronavirus outbreak. This is furthered by sensationalised headlines being used to target intended demographics in the context of the current pandemic.

References:

[1] Wikipedia, https://en.m.wikipedia.org/wiki/Plague_doctor, (accessed July 2020).

[2] Live Science, https://www.livescience.com/bubonic-plague-inner-mongolia.html, (accessed July 2020).

[3] Science Daily, https://www.sciencedaily.com/terms/bubonic_plague.htm, (accessed July 2020).

[4] Encyclopedia.com, https://www.encyclopedia.com/medicine/diseases-and-conditions/pathology/enterobacteriaceae#:~:text=Enterobacteria%20are%20bacteria%20from%20the,meningitis%20%2C%20septicemia%2C%20and%20pneumonia%20, (accessed July 2020).

[5] R. Yang, Journal of Clinical Microbiology, 2018, DOI: 10.1128/JCM.01519-17

[6] Abc News, https://abcnews.go.com/Health/plague-exists-now-us/story?id=55860883 (accessed July 2020).

[7] World Health Organization, https://www.who.int/news-room/fact-sheets/detail/plague, (accessed July 2020).

[8] Science Museum, https://www.sciencemuseum.org.uk/objects-and-stories/medicine/bubonic-plague-first-pandemic#the-black-death, (accessed July 2020).

[9] Ancient History Encyclopedia, https://www.ancient.eu/article/1540/medieval-cures-for-the-black-death/, (accessed July 2020).

[10] DrugBank: Streptomycin, https://www.drugbank.ca/drugs/DB01082, (accessed July 2020).

[11] Dr J. D. Poland and Dr D. T. Dennis, in Plague Manual: epidemiology, distribution, surveillance and control, World Health Organisation, 1999, ch. 3, pp. 55-60

[12] Open Learn, https://www.open.edu/openlearn/science-maths-technology/science/biology/vaccination/content-section-4.3 (accessed July 2020).

[13] History of Vaccines, https://www.historyofvaccines.org/content/articles/different-types-vaccines, (accessed July 2020).

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