735–737 Japanese smallpox epidemic

Origins

A few decades prior to the outbreak, Japanese court officials had adopted the Chinese policy of reporting disease outbreaks among the general population. This recording practice greatly facilitated the identification of smallpox as the disease that afflicted Japan during the years 735–737.

Increased contact and trade between Japan and the Asian mainland, directly and through Korea, had led to more frequent and serious outbreaks of infectious diseases, including smallpox. The smallpox epidemic of 735–737 was recorded as having taken hold around August 735 in the city of Dazaifu, Fukuoka in northern Kyushu. The infection had ostensibly been carried by a shipwrecked Japanese fisherman who had contracted the illness after being stranded on the Korean peninsula. The disease spread rapidly throughout northern Kyushu that year, and persisted into the next year. By 736, many land tenants in Kyushu were either dying or forsaking their crops, leading to poor agricultural yields and ultimately famine.

Also in the year 736, a group of Japanese governmental officials passed through northern Kyushu while the epidemic was intensifying. As members of the party sickened and died, the group abandoned its intended mission to the Korean peninsula. Returning to the capital with smallpox, the officials helped spread the disease to eastern Japan and Nara. The disease continued to ravage Japan in 737. One manifestation of the pandemic's great impact was that by August of 737, a tax exemption had been extended to all of Japan.

Based on fiscal reports, adult mortality for the smallpox epidemic of 735–737 has been estimated at 25–35% of Japan's entire population, with some areas experiencing much higher rates. All levels of society were affected. Many court nobles died due to smallpox in 737, including all four brothers of the politically powerful Fujiwara clan: Fujiwara no Muchimaro (680–737), Fujiwara no Fusasaki (681–737), Fujiwara no Umakai (694–737), and Fujiwara no Maro (695–737). Their sudden departure from the royal court allowed for the ascension of noted rival Tachibana no Moroe to a high official position in the court of Emperor Shōmu.

The epidemic not only killed a large segment of the population, it triggered significant dislocation, migration, and imbalance of labor throughout Japan. Highly affected occupations included construction and farming, especially rice cultivation.