Plague! The Black Death and Its Impact on Public Health

by Katherine Callaway on February 20, 2014


Representation of “The Dance of Death”, a Medieval belief inspired by the plague that victims would rise from their graves to tempt others to join them in death

Plague.  It’s a word that elicits both fear and a sense of morbid curiosity.  Whether you imagine a zombie apocalypse or the mysterious, beak-masked figure of a medieval doctor during the Black Death, plague is one of those ideas that both fascinates us and sends tingles down our spines.  What about this particular disease holds our attention? How has plague shaped our perceptions of pandemic disease and, more importantly, how has it shaped our practice of public heath?

Despite its colloquial use to describe any major disease outbreak, “plague” is actually a very specific diagnosis. Caused by the bacterium Yersinia pestis, plague takes three distinct forms: bubonic plague, septicemic plague, and pneumonic plague.  Pneumonic plague is the most recognizable of the three. According to the Centers for Disease Control (CDC), patients with pneumonic plague “develop fever, headache, weakness, and a rapidly developing pneumonia… Pneumonic plague is the most serious form of the disease and is the only form of plague that can be spread from person to person (by infectious droplets)” (CDC). The introduction of the plague bacterium into human populations usually occurs through direct contact with infected rodents or with the fleas that feed on them.  Although historical outbreaks like the European Black Death were concentrated in urban centers, the CDC reports that most plague cases now occur in rural areas with large rodent populations.


“Plague Doctor” during the Black Death Pandemic in Europe (1300s-1400s)

The history of plague is inextricably intertwined with the development of modern public health.  The most famous plague pandemic, the Black Death, arose in Europe during the 1300s and 1400s.  This huge outbreak was largely due to the poor sanitary conditions in medieval towns. The collapse of the Roman Empire meant that many towns did not have the basic infrastructure needed to prevent disease outbreaks- including orderly waste disposal.  Instead, people lived in crowed fortress cities, often in the same rooms as animals such as chickens, pigs, and, of course, rats that fed on piles of garbage and animal waste.  One can only imagine the public health hazard (not to mention the smell) of these fortress cities.  They were the perfect place for plague to take hold.

Although current estimates suggest that the Black Death killed up to 50% of Europe’s total population, it also represented a major milestone in the development of modern public health.   In his classic book “A History of Public Health,” George Rosen explains how the Black Death pandemic in Europe triggered the development of many fundamental public health practices.  He states that, “[S]tirred by the Black Death… public officials…created a system of sanitary control to combat contagious disease… This system is still a part of public health practice today…” (45).  During the Black Death, appointed health officials isolated plague patients in special hospitals for forty days (hence, the development of quarantines), fumigated the houses of those who had died, and screened visitors for plague-like symptoms before letting them into the town.  “While medieval community did not have an organized public health system in the present-day sense, it did have administrative machinery for disease prevention, sanitary supervision, and, in general, protection of community health” (Rosen 47).   Although the Black Death still claimed a large proportion of Europe’s total population, it also left a profound impact on the practice of  public health.  The advances made during the Middle Ages continued to develop during the Renaissance and Enlightenment.  However, it was not until the Industrial Revolution that plague once again took center stage.

As mentioned previously, plague spreads best when people come into close contact with infected rats or fleas.  During the Black Death, such contact was the result of humans and animals living together in small, dirty spaces.  The plague outbreaks of the late 1800s and early 1900s can also be attributed to human-rat contact.  During this time period, industrialization led to urbanization as huge numbers of people began to settle around the factories where they worked.  Unfortunately, building regulation was not the same as it is today.  Urban slums in seaside industrial centers gave the plague bacteria the perfect opportunity to jump from rats to fleas to people.  According to the CDC, the Modern Plague began in China in the 1860s and soon spread to the rest of the world via infected rats on trading vessels.  This “third pandemic” (after the 6th century Justinian Plague and the Black Death) is ongoing and has caused over 10 million deaths since it began (CDC).

Fortunately, the reintroduction of plague in the late nineteenth century coincided perfectly with the development of modern medicine and environmental public health. Conventional wisdom against “miasma” or “dirty humors” in stagnant water or open sewage had been around since the Roman era.  With the development of germ theory in the late 1800s, however, scientists began to understand that plague was caused not by “miasma,” but by a bacterium that spread from person to person. By studying this bacterium, they discovered that it could survive in some conditions, but not in others.   This new knowledge was a huge leap in the field of public health because officials finally began to realize that they could prevent disease by regulating human environments.  A new contingency of “sanitarians” believed that public cleanliness could prevent disease by creating a hostile environment for disease-causing agents like the plague bacterium.  They were responsible for the formalization and standardization of many fundamental public health measures, including organized waste management.


“Rat Receiving Station” during the 1900-1909 San Francisco Plague Outbreak

The biggest environmental public health advance during the Modern Plague, however, came in the form of pest control. In 1903, plague prevention efforts were revolutionized by the discovery that rats were the main vectors of the Yersinia pestis bacteria.  A 1920 report to the American Public Health Association stated that “If we are economically and efficiently to ward off plague we must rid ourselves of the rat… Rat destruction and rat-proofing are preventative measures that fortunately do not involve financial loss, while they will eliminate the dangerous rodent from the homes and environment of men” (Simpson 1).  Newly developed Public Health Agencies sent corps of workers to trap the pesky rodents and to make sure that buildings were up to code.  In addition to trapping and killing any rats that were unfortunate enough to come into their paths, these officials checked for things like cement basements instead of cheap wooden basements that could easily be infiltrated by rats or other cur rowing rodents.  There was also a new interest in developing chemical methods of pest control- for example, fumigants like hydrocyanic acid to kill any remaining fleas after the rats were killed.   The different plague outbreaks in the late nineteenth and early twentieth centuries therefore issued in a new era of environmental public health- one that focused on clean cities and population control of animal disease vectors.

So how does plague affect public health today?  Throughout its history, this disease has had an important role in shaping our practice of community health.  Today, the WHO reports between 1,000 to 2,000 new plague cases per year, mostly in small agricultural villages in Africa (CDC).  Modern antibiotics and city sanitation mean that plague is no longer the black scourge that so many of our ancestors feared.  However, it is important to remember that many health measures that we take for granted today were developed during the major plague pandemics of past centuries.  Plague has left an indelible mark on human populations not only as a “black death”, but also as a catalyst for the improvement of public health practice.

Author: Katherine Callaway


Centers for Disease Control. (2012, June 13). Plague. Retrieved from

NIH (2009, March 6). Plague Doctor [sketch]. Retrieved from

PBS (1998). Rat Receiving Station [photograph]. Retrieved from

Dance of Death. Retrieved from

Rosen, George. (1993, July 1). A History of Public Health. Retrieved from fUJ8iECMC

Simpson, F. (1920, September 15). Methods of Plague Control. The American Journal of Public Health, n.a. 845-850. Retrieved from

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