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.

Variants of the Plague

The bubonic plague had three main variants: septicaemic, pneumonic, and bubonic. These variants occurred in different regions across Europe, the Middle East, and Asia.⁷ The bubonic plague was the most common and recurrent form. It had an incubation period of six days, after which a blackish, gangrenous pustule would appear at the site of the flea bite. This was followed by the swelling of lymph nodes in the neck, groin, or armpit — depending on which area was closest to the bite location.⁸ As the disease advanced, subcutaneous hemorrhaging would begin, eventually causing swelling and the development of purple or black blotches in the lymphatic nodes, giving rise to the name "Black Death." The hemorrhaging caused intoxication and damage to the nervous system, resulting in psychological and neurological disorders.⁹ Victims of the bubonic variant often suffered from diarrhea, vomiting, and pneumonia. The bubonic plague had a fatality rate of 50% to 60% among the infected.

The septicaemic variant was the rarest and most lethal form of the plague. Like the bubonic plague, this variant was transmitted by fleas (X. cheopis) rather than from person to person. It occurred when a victim's bloodstream was overwhelmed with bacteria, typically within only a few hours. Due to the extremely high fatality rate, victims would succumb before the symptoms characteristic of the bubonic variant — such as swelling of the lymphatic glands — could emerge.¹⁰ The concentration of bacteria in the victim's bloodstream was profound. When a human flea bit an infected person, it would contract the bacteria and transmit it to subsequent hosts. In this form, the human flea (Cortophylus fasciatus) served as the primary vehicle for transmission among humans.

The pneumonic plague was the only contagious variant and could be transmitted directly from one individual to another.¹¹ Following an incubation period, the body temperature would drop for two to three days, accompanied by severe coughing. The infection attacked the lungs, causing consolidation followed by the discharge of bloody sputum. Coughing dispersed bacteria into the air, and the sputum itself carried bacteria, further accelerating transmission. After the lungs were attacked, victims would suffer neurological deterioration and eventually fall into a coma.¹² The pneumonic variant had a fatality rate of 95% to 100%.

Conclusion

The bubonic plague wiped out China's population from approximately 120 to 60 million people and stands as one of the most devastating pandemics in recorded history. The expansion of trading routes increased access to European and Asian markets and simultaneously accelerated the spread of the disease. The Mongols, unable to control trade peacefully, seized territories by force, and Tartar warriors attacking eastern Europe created additional pathways for the bubonic plague to spread. The impact of the Black Death on the Chinese population may have been even greater than the records indicate, given the concurrent loss of life from floods, tribal wars, and the limitations of census methodology. The northern regions of Hebei and Shandong experienced the most devastating population shrinkage, and the political consequences — including the fall of the Yuan Dynasty and the rise of the Ming Dynasty — reshaped China's governance for generations. Ultimately, the Black Death in China was the product of intersecting forces: the biology of Yersinia pestis, the ecology of flea-rat transmission, the expansion of medieval trade networks, and the volatile political landscape of Mongol rule.