PRINCETON, U.S.A. People have assigned the category “plague” to several pandemics for centuries and its witnesses have evoked mass death with dramaturgy and urgency. During the Jusitinian plague of 541 CE, the sixth-century Syrian John of Ephesus said: “And so great was his distress, and the inflammation caused by the five plagues, which encompassed his body within and without, that he wept and lamented.” During the Black Death of 1347-1351, medieval historian Jean Froissart claimed that over a third of the population died from this disease. In the pre-modern period, the plague was generally documented in liturgical retorts, historical palimpsests, and military diaries. On rare occasions, early modern predecessors such as Baron François Gérard illustrated the apocalyptic undertones of this pestilence through such paintings as “Peste de Marseille”.

Nonetheless, the isolation of the microorganism Yersinia pestis in 1917 and its genomic sequencing in 2011 has opened up a new door for understanding the biological, genetic, and phylogenetic transformation of the disease. Most people are familiar with the classic narrative of the Black Death, the transmission of the bubonic plague from fleas to rats and then to unsuspecting humans. Yet, few can imagine the conditions that causes one strain to be more virulent than another. While there are debates about Y. pestis’s genetic variation, Kristen Bos and her colleagues generally agree that there was an ancient bacterial strain that bears resemblance to the modern plague. The new study by researchers at McMaster University published in Lanccet Infectious Diseases suggests that the Y. pestis strain from the sixth century branched off into two distinct strains thus resulting in divergent disease outcomes for contemporary human and rodent populations. That is to say that modern rats could pose a distinct threat from their Justinian antecedents of 541. For any person trained in biology, this should not sound too surprising since microorganisms constantly undergo replication and are susceptible to mutation. However, what is unusual is that the modern plague, when hosted by contemporary human and murine populations, is more treacherous than the sixth century bacterium. This surely rings some alarms among science commentators.

Science Daily expressed concern about the future impact of the plague in the following way: “These findings [by David Wagner et al] suggest a new strain of plague could emerge again in humans in the future.” Indeed, biological agents have the potential to become an epidemic but it happens in the context of economic, environmental, and political conditions external to the pathogen itself. Two prime examples of this include the Black Death of 1347-51 and the Influenza outbreak of 1919—each killing 30 and 18 million people, respectively. Yet, these epidemics coincided with political and economic transformations that helped ignite the upsurge. Regarding the Black Death, Rutgers University historian Robert S. Gottfried has documented the economic and political transformation leading up to the fourteenth-century Black Death and concluded that a host of material conditions, including malnutrition, assisted the disease’s devastation. Additionally, the Influenza pandemic proliferated during the final years of World War I, a period where there was significant displacement and trench warfare. While genetic factors are important considerations for understanding the potential threat of future pathogens, environmental conditions are mediators for the perils of microorganisms.

If the bubonic plague or any epidemic becomes a threat more can be done with respect to preventive and therapeutic measures. For example, providing clean water, nutrient rich foods, and access to health facilities are the integral to minimizing the spread of disease. These measures go a long way in improving people’s immunity and providing the ingredients for combating disease. In economically poor countries that might entail building the capacity of local governments to provide free access to medical care. Another significant shift has been the introduction of antibiotics, which can significantly reduce the spread of Y. pestis.

Therefore, while the pestilence did evoke imminent death upon earlier societies, modern public health measures can shift the tide of history from dramaturgy to pragmatism. So, although the pathbreaking scientific research on Y. pestis‘s genetic transformation suggests that the bubonic plague could be a future threat, it actually opens up new possibilities for interdisciplinary research and preventive care.