Humankind’s encounters with plagues are steeped in antiquity, although not all of them implicate the plague bacterium. Allow me take you through the historical mentions.
In the Hebrew Old Testament, 1 Samuel (or Shmuel) Chapter 5 verse 6 and Chapter 6 verse 5 mention a plague of t’chorim (large intestine), which has been translated variously as hemorrhoids or tumors, as well as a land-destroying infestation of mice; the allusion to mice makes it plausible that a zoonotic plague, such as due to the Gram-negative bacillus Yersinia pestis – which I introduced in the previous part of this series – may have taken place. Again, Zachariah (or Zechariah) Chapter 14 verse 18 mentions a plague ‘similar to that of Egypt’. Greek historian Thucydides described a devastating epidemic disease, known as the Plague of Athens, that came via Africa during the last third of 5th century BCE; however, the modern consensus deems the typhoid bacillus, some viral infection, or viral hemorrhagic fever as possible causes. Egyptian historian Manetho, at early 3rd century BCE, noted pestilences in Egypt. In the same century, an outbreak of plague occurred in Libya and Syria, which was reported by the Greek physician of 1st century CE, Rufus of Ephesus, who described a disease with buboes (i.e. painful swellings of the lymph nodes). Historian William H. McNeill, seeking to unravel the enduring mystery of the fall of the mighty Roman empire, propounded that the Romans succumbed to two severe and protracted plagues, the Antonine Plague (165-180 CE), and the Plague of Cyprian (250 through 270 CE) – although these are now considered to have been due to some virulent viral infection, possibly smallpox.
Human history has documented three plague pandemics: the first one is the Justinian Plague of 541 CE, named after the contemporaneous Byzantine emperor Justinian I; spreading from Egyptian port city of Pelusium, it continued sporadically over next couple of centuries, and exacted a tremendous toll, affecting the entire medieval Mediterranean basin (Constantinople, Syria, Anatolia, Greece, Italy, Gaul, Iberia, and North Africa) and hinterlands of Ireland in the north and Persia in the east. According to historians, both contemporary and modern, this plague appeared in no less than eighteen waves in the region, lasting until the middle of 8th century CE, and is considered to have contributed to the fall of the Roman Empire.
The second pandemic is referred to as the Great Plague or “Black Death” (due to the appearance of black spots and black discoloration of necrotic, hemorrhagic, gangrenous skin), which lasted from the mid-14th century until the 19th century CE. Spreading from Central Asia and/or China along the great trade route (the Silk Road), and partly via naval vessels, it reached seaports of Western Europe in 1347 and quickly spread through continental Europe within the next couple of years, striking Sicily, Italy, France, Spain, Portugal, England, Germany and Scandinavian countries, reaching Russia in 1351. During the same time frame, it also devastated the Middle East and regions to the north and east of the Mediterranean basin and Asia minor. In Western Europe, this second pandemic lasted for nearly 500 years, returning periodically; although accurate statistical estimates are unavailable, an estimated 100 million people of the world succumbed to this scourge. At the same time, some historians surmise that massive labor shortages resulting from the vast number of deaths may have accelerated many economic, social, and technical developments, perhaps even leading to the emergence of the Renaissance in the late 14th century.
The third pandemic, the Modern Plague, began in Yunnan province of China in 1855, reached Hong Kong by 1894, and within next 20 years, it devastated colonial India (causing about 10 million deaths), and spread to port cities around the world by rats on steamships. In 1894, French bacteriologist Alexandre Yersin, then working as a shipping company doctor in Hong Kong, managed to isolate the plague bacillus, and determined the mode of transmission; in 1989, another French physician, Paul-Louis Simond, demonstrated how the vector, the fleas, transmit the plague bacterium from host to host. Although his theory was initially disputed, his and Yersin’s work have been instrumental in understanding the epidemiology of plague and devising public health measures to control this menace.
Even now, smaller outbreaks of plague continue to occur sporadically in parts of the world, amongst which Africa accounts for almost 95% of world totals, and the rest is reported in Peru (Western South America), the Western US, and parts of Asia.
Asymptomatic cases of Yersinia pestis has been recently reported in the Qinghai Province, China, amongst folks who hunt the Himalayan Marmot, a type of large ground squirrels. The lack of symptoms may, in part, be due to their practice of taking prophylactic antibiotics. Apart from Marmots, small rodents, such as Gerbils and Jerboas, have been shown to carry Yersinia pestis in Mongolia, where human infections have been documented since 1940s.
The United States, where plague first visited in 1900 via rat-infested steamships sailing from Asia, is no stranger to the deadly disease; epidemiologists have identified two US zones of endemicity in the rural and urban western and mid-western states containing semi-arid upland forests and grasslands inhabited by many rodent species; these zones include Northern New Mexico, northern Arizona, and southern Colorado in one, and California, southern Oregon, and far western Nevada in the other.
It is because of the current level of anti-plague medical armamentarium, as well as established public health and sanitation policies, that plague now fails to cause widespread suffering and is reasonably contained. However, given that in the modern times, the issue of emergence of new and re-emergence of antiquated infectious diseases is a major concern in public health, plague remains a major discussion amongst physicians, epidemiologists, and medical historians.
Up next is the final part of this series where I describe how the plague bacterium Yersinia pestis came to be attributed as the etiological agent of plague pandemics in history. The answer is not as straightforward as one may think. Stay with me!