The bacterium Yersinia pestis (Y. pestis) was responsible for the Justinian Plague, Black Death, and the Modern/Bubonic Plague (Plague History PPT, slide 3). The plague-causing bacterium is carried by fleas, who carry the bacterium to rats. When the rat dies, if no other rats are readily available, the flea finds a human to which it transmits the infection via biting and vomiting (slides 4 and 9).

Societal factors contributed to the virulence of these plagues. For example, the increased crowding of people throughout time led to the increased ability for air borne transmission; the plagues were much more fatal when pneumonic than septicemic (slide 12). Additionally, expanding trade networks linked cultures together like never before, further enabling the spread of the disease from country to country (slide 34). With ~100 million Eurasian deaths, there were also mounds of rotting cadavers due to the inability to bury such a large number of bodies (slide 38).

Fear over the highly lethal outbreaks led to an equally sized outbreak of blame. Such blame was largely targeted towards the Jews, who were occasionally massacred (slide 40). In a more practical attempt to control the transmission of plague, however, quarantine was introduced in 1377; 40 days was chosen for a number of reasons, to include biblical explanations, Hippocratic theories, and mathematical justifications (slide 43). Networks of spies were also introduced in order to provide an intelligence surveillance system (slide 44). Plague hospitals were also developed, wherein the sick were isolated and confined (slide 45). Western cultures more-so blamed poor sanitation for the plague, and thus isolated victims as well as their contacts, burned clothing and cadavers, and even fumigated houses/slums (slide 60). In Hawaii, any buildings suspected of containing a source of the disease was to be burned by order of the Board of Health (slide 61). Immigrants lost personal freedom, having been forced into quarantine and even forced to receive experimental vaccines (slide 68).

Today, more is known about plague transmission, to include its tendency to be spread from one non-human species to another, before it is in turn transmitted to humans. Additionally, it is likewise known that these transmission from one species to another are more common in cooler summers that follow wet winters (Plague Today, slide 12). Moreover, transmission in the U.S. is commonly through flea bites, contact with contaminated fluid or tissue, and infectious droplets (slides 17-19). Household pets (dogs, cats, etc.) can also serve as middle-men in the transmission from urban/rural species to humans (slides 13, 17, and 20).

The most recent resurgence of plague was in Madagascar after 2009, where there are 300-600 cases per year. This is largely the result of political upheaval and financial cutting of basic government services. This has led to millions of people in poverty, the closure of hundreds of health clinics, lack of funding for clean water and infrastructure, poor hygiene, and the accumulation of trash in the streets (which in turn led to increased numbers of rats) (slide 29). Additionally, although plague victims are to be buried immediately near a city hospital, many families in Madagascar unbury their loved ones to bury them in their villages. Other families also decide not to bring their loved ones to hospitals at all in order to keep them from being buried by health care officials. Moreover, the lack of health care facilities has led to the rise in traditional healers, who use hand mirrors which allow the healers to receive advice from ancestors. Such traditional healers have at times used spit as treatment for their patients (slide 31). Also, villages typically keep their animals (cattle, chickens, etc.) and crops in their homes, which gives rise to rats and fleas (slide 32).

Throughout history, it has become quite clear that human behavior and decisions impact the rise and spread of disease. Harmful cultural traditions, inept necessary funding, poor sanitation, lack of education, and pseudoscience (e.g., anti-vaccinationists) continue to harm the well-being and safety of communities and the world at large. Failure to pay attention to past events, such as historic plagues, as well as the present, such as in Madagascar, bars us from important, useful information.