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July 29/August 5, 2002
 Erica Seiguer Photo by Graham Ramsay |
The Plague: Historical Killer, Modern Menace
Over the centuries, Yersinia pestis, the etiological agent of bubonic plague, has been conceived--and misconceived--in various guises. Before germ theory, modern medicine, and any real concept of public health and epidemiology, the disease, which killed off a third of Europe's population in the mid-14th century, was attributed at different times to moral depravity, a Jewish conspiracy, snakes or serpents, and contaminated air. The book In the Wake of the Plague: The Black Death and the World It Made by medieval historian Norman Cantor explains that a group of French scholars, commissioned by the king to come up with the real explanation, arrived at the conclusion that the pestilence ravaging Europe was related to the planet Saturn and its relationship with Jupiter. Cantor describes how the most intelligent and powerful leaders of the day were helpless in the face of this disease.Their theories, along with the associated remedies, may seem preposterous by today's standards, when the bacterium's genome has been sequenced, stripping the organism bare. For a moment, however, consider life at the time of the Black Death around 1348, which was, to paraphrase, short and very, very brutish.
A Democratic Death
In Europe, where the plague changed the course of history, neither wealth nor position could save the plague's victims. Archbishops, princes and princesses, lords and ladies, as well as thousands and thousands of serfs and yeomen who lived a very different existence from the rich, all died in the same way. Without any concept of transmission or public health measures, the rich and poor alike fell prey to the swollen, dark, pus-filled lymph nodes and high fevers. The quick death that Yersinia wreaked was the inspiration for the Italian writer Boccaccio's description of the plague's victims who "ate lunch with their friends and dinner with their ancestors in paradise." Because of the complicated arrangements around inheritance and property, the death of one family member could alter the lives of generations to come, forcing them into poverty or lifting them into the gentry class.The most recent major outbreak of plague occurred in India in September 1994, and though there were only about 146 cases and 54 deaths, the lack of information generated confusion and panic both in India and around the world. As word of plague spread, mass hysteria caused 500,000 people to flee the area.
From Boccaccio to Biowarfare
Beyond the remarkable history of the lowly Yersinia pestis, threats of biological warfare make plague a contemporary concern for policymakers and the public at large. The bacterium is the cause of both bubonic and pneumonic plague. While there are up to 3,000 cases of plague around the world each year, including about 10 to 15 sporadic cases in the U.S., terrorist use of the bacterium could explode these numbers.Among the various biological agents identified by the Centers for Disease Control and Prevention as threats to the public health, plague is in apporpriate company with smallpox, anthrax, and botulism. The transmission dynamics of the bacterium make it an ideal candidate for would-be terrorists. The bug could be used in an aerosol attack and affected individuals would develop symptoms of pneumonic plague in one to six days, allowing them to travel widely and spread the disease before being diagnosed. Treatment of infected individuals should be administered within 24 hours, and exposed individuals must be treated within seven days of exposure. If untreated, patients progress to respiratory failure and almost always death. While several antibiotics are available, there is currently no vaccine for pneumonic plague.
Y. pestis has been studied by numerous scientists and is therefore readily available in labs across the country and around the world--more so than smallpox, for example. A simulation experiment conducted by the World Health Organization found that 50 kg of aerosolized Yersinia dropped over a city of 5 million would lead to around 150,000 cases of pneumonic plague and 36,000 deaths. The panic in the face of such an attack, it is thought, would overwhelm public services.
In the mid 1300s, the Tartars catapulted the corpses of those who had died from plague into the city walls of Kaffa in the Ukraine, which they were trying to invade. It is one of the first examples of the use of Yersinia as an agent of biowarfare. In the early 18th century, the Russian army tried the same technique in an effort to devastate the Swedes occupying Reval in Estonia. During World War II, the Japanese military conducted research on the use of Yersinia and other biological agents on prisoners, resulting in about 10,000 deaths. The history of biological warfare, and specifically the use of plague, is a long one. And, one hopes, it will remain just that: history.
--Erica Seiguer, a fourth-year MD-PhD student at HMS
Websites of Interest:
CDC Public Health Emergency Preparedness and Response, Plague
Johns Hopkins Center for Civilian Biodefense Strategies, Plague
The Sanger Institute, Yersinia pestis
The opinions expressed in this column are not necessarily those of Harvard Medical School, its affiliated institutions, or Harvard University.