Epidemics and mortality

Japan's prophylactic good luck

By William Wetherall

A review of
Ann Bowman Jannetta
Epidemics and Mortality in Early Modern Japan
Princeton: Princeton University Press, 1987
xxii, 224 pages, hardcover

A version of this article appeared as
"Japan's virulent imports" in
Far Eastern Economic Review, 143(3), 19 January 1989, page 47

This book grew out of Ann Bowman Jannetta's desire to learn whether the outbreaks of bubonic plague that periodically decimated Europe between the 14th and 17th centuries caused similar destruction in Japan. Plague failed to reach Japan, and "it is possible that the absence of trade in grain between Japan and other countries prevented the transfer of the necessary hosts and carriers to Japan."

The epidemic diseases that were prevalent in pre-modern Japan were smallpox, measles, dysentery and cholera -- important epidemic diseases in all urbanised societies of the pre-modern world. She found that smallpox, the biggest killer in Japan, was endemic in the country as a whole by the late 12th century and probably earlier.

Measles reached Japan by the 10th century but never became endemic in the country's population of 30 million. In the second half of the 19th century, measles was still an imported disease that spread but soon died out each time it was introduced by carriers arriving at Nagasaki. Jannetta calls this anomaly in the history of measles. how could the virus have died out in such a large population? One reason measles failed to become endemic in japan was probably the distribution of its pre-modern population.

Measles hit Japan every 20-30 years. The disease began in Nagasaki and spread eastward along the coasts, first to the populations along the major transportation routes, then to remote inland settlements, and finally to the sparsely populated north.

Dysentery epidemics are described in early accounts thought not as frequently as outbreaks of smallpox and measles. Local death records show that mortality from dysentery varied considerably among villages in the same region, which "warns against any general conclusion about the overall importance of enteric disease as a cause of death in early modern Japan."

Japan's position and relative isolation probably made it more difficult for some diseases to reach the islands. The only explanation for the absence of cholera epidemics in japan between 1822 and 1858, when the disease circled the world many times, is that "people who were infected with cholera did not enter Japan and contaminate the food and drinking water there."

But Jannetta concludes that since "certain diseases failed to reach Japan despite the fact that foreign trade with neighbouring Asian countries continued throughout the Tokugawa period," Japan's geographical position and insularity must be only part of the answer. it seems likely that "the Japanese may have played an active role in keeping foreign diseases out of the country. For example, Japanese port officials may have tried to identify and quarantine ships that had visibly sick persons aboard."

Whatever the source of Japan's prophylactic good luck, it is clear that the archipelago lost all of its "immunity" to cholera and some other exotic diseases when it opened its ports to the outside world in the middle of the 19th century. The epidemic of Asiatic cholera that ravaged Japan in 1861-1862 reportedly claimed 150,000 lives in Tokyo alone.