The Black Death Plague in 14th-Century China: Origins and Impact

Introduction

The cause of the Black Death was only recently hypothesized and proven to be Yersinia pestis, with scientific advancements made in the 18th and 19th centuries. The pandemic that reduced the Chinese population from approximately 120 to 60 million people is now recognized as the bubonic plague. In the 19th century, the epidemics that riddled Asia, the Middle East, and Europe between 1347 and 1670 were attributed to the bubonic plague.¹ The ancient medicine practiced in China, where the plague had a devastating impact on the population, was still rudimentary and stemmed from cultural practices and the medical advancements made by Aristotle and Hippocrates in the 4th century.² The origins of the plague were traced to Siberia and Mongolia. This paper explores the pathology, spread, and socio-economic and political impact of the bubonic plague, including a review of the Black Death in China.

Pathology of Yersinia Pestis

The Black Death resulted from a variety of bacteria classified under Yersinia pestis. The origin of the bacteria is believed to be the Mongolian Steppes around 1331. Between 1347 and 1350, the bacteria had spread across Asia, Europe, and North Africa.³ The bacteria typically live in the stomach of rat fleas and may also inhabit the stomach of the human flea. The bacteria block the flea's digestion, and as the flea feeds, it regurgitates the bacteria from its stomach into the victim's body.⁴ The point of entry of Y. pestis into the human body is a break in the skin, though access is limited when the skin is healthy. Since rodents infested with fleas — such as marmots, tarbagans, and susliks in Asia — were virtually present in every household from the 14th to the 16th century, they would attack human beings after exhausting their rodent hosts. Humans thus became victims of an epizootic disease.

The survival conditions for Y. pestis in the absence of rodent hosts require temperatures between 59°F and 68°F with humidity between 90% and 95%. Where humidity drops below 70%, rodent fleas (Xenopsylla cheopis) are unlikely to survive.⁵ This explains why the plague was experienced at lethal rates during late summer and early spring, when climatic conditions were most suitable for flea survival. When the rodent population increased due to food availability, the bubonic plague would resurface.⁶ Once the rodent population declined, Y. pestis would survive in rodent burrows for prolonged periods, as these environments are dark and moist. When new populations of rodents moved into these burrows, they would become infected, triggering a new epidemic. Consequently, the Black Death in China resulted not from a single outbreak but from a cyclic recurrence of epidemics that made the disease more fatal than its virulence alone would suggest, helping to explain the catastrophic population losses associated with the Black Death.