The Dissemination of Disease Within East Asia

By late Han times Chinese culture began to spread to the other regions of East Asia. As the indigenous peoples of Korea and Japan began to adopt irrigated, wet-rice agriculture, their numbers increased, cities were built, and these countries began to be afflicted with the civilized diseases of China.

Japanese accounts of smallpox epidemics in A.D. 585 and 735-7 provide excellent early descriptions of this disease. The smallpox epidemic of 735 came from the kingdom of Silla in southern Korea. It began in the part of Kyushu nearest to Korea, and it spread toward the major population centers in the region around the capital at Nara. Although this was not Japan’s first smallpox epidemic, it caused high mortality among all age groups in the popula­tion, indicating that smallpox epidemics did not reach Japan very frequently. Wayne Farris believes that high mortality from virulent, imported diseases between 645 and 900 caused Japan to suffer a demo­graphic setback that had a major impact on Japan’s political, economic, and social development in this early period.

Once imported epidemics reached Japan, the di­rection of spread was invariably from the south­west — where ports of entry for foreign ships were located - to the northeast along routes where Ja­pan’s population was concentrated. Japan had a high population density very early in its history, and as in China, most diseases became endemic with little difficulty. Smallpox was clearly endemic in Japan by the twelfth century and probably well before (Jannetta 1987).

The more sparsely settled and remote areas of East Asia could still be seriously threatened by se­vere epidemics as late as the seventeenth century.

During the seventeenth and eighteenth centuries, the dissemination of disease intensified as these pe­ripheral regions were gradually incorporated into the main networks that operated in East Asia. Sev­eral factors contributed to this intensification pro­cess: East Asian populations increased in size and density, urbanization accelerated in both China and Japan, contact between core and periphery in­creased, and activity on China’s frontier intensified.

Changes in tribute relations accompanied the con­solidation ofTokugawa and Ch’ing power in the sev­enteenth century, and promoted the dissemination of disease within East Asia. Between 1637 and 1765, contacts between China and Korea increased: An average of 3.8 tribute missions a year traveled from Korea to Peking, and in fact Korea and the Ryukyu Islands sent tribute missions to Japan as well. The King of the Ryukyus was regularly required to pay his respects to the daimyo of Satsuma and on occa­sion to the Tokugawa shogun in Edo (Sakai 1968). In Japan, the shogunate institutionalized contact be­tween core and periphery with the creation of the sankin-kotai system. This system required that large numbers of retainers travel to Edo from each of the provinces in alternate years to pay attendance upon the shogun. All of these activities would have increased the rate of disease dissemination in Japan.

The development of interregional trade in Japan also served to disseminate density-dependent dis­eases throughout the islands. As outlying regions were drawn into a more widespread market net­work, they were also incorporated into a wider net­work of disease dissemination. Local records show that epidemics became more frequent in the hinter­lands of Japan during the Tokugawa period.

On the East Asian mainland, the disease ecology of China began to expand across the northern frontier. To the north and northwest the range of Chinese expansion had been sharply limited. The steppes of Mongolia and Manchuria and the high Tibetan wastes had no great river systems from which water could be drawn to support intensive, irrigated agri­culture, and a pastoral society that stood in stark contrast to that of China had developed on China’s northern frontier. The steppe had become the home of nomadic tribes whose wealth was moveable herds of livestock, not land or grain. The Great Wall of China, built to keep out the “barbarian” peoples who raided Chinese settlements, marked the frontier between two fundamentally different cultures.

The Great Wall also marks the frontier between the two major disease ecologies of East Asia. The dispersed and mobile populations north of the Great Wall had much less exposure to human pathogens than did the densely settled populations to the south. And because of infrequent exposure they were extremely vulnerable to the civilized diseases of China.

During the late Ming (1368-1644) and early Ch’ing (1644-1911) dynasties, Chinese civilization began to encroach on territories to the north, and there was increasing contact between northern Chi­nese and the nomadic peoples of the steppe. China’s traditional policy had been to forbid trade with these barbarian enemies.

The numerous military campaigns of the late Ming period required large supplies of horses. In the second half of the sixteenth century, the Chinese set up official horse markets on China’s northern fron­tier, where cloth and grain were exchanged for Mon­gol cattle, sheep, mules, and horses. Initially there were four market locations - at Tatung, Hsuan-fu, Yen-sui, and Ningsia - where horse fairs were held during the spring and summer months. In time, smaller markets were added at other places along the Great Wall where forts were situated. These small markets permitted Mongols who lived near the frontier to come to trade once or twice a month, and the regularization of these markets provided a more dependable supply of goods for Chinese and Mongol alike (Hou 1956). At the same time, more frequent contact between Mongols and Chinese per­mitted the dissemination of the density-dependent diseases of China to the tribal peoples of the steppe.

The disease problems that followed the growth of fairs and the border trade in the second half of the sixteenth century are documented in both Chinese and Mongol sources. The Mongols were most fearful of smallpox, which was rare in Mongolia. The biogra­phy of Tu T’ung, a military commander in Shensi, tells of an incident in which men returning from the border caught smallpox and died. The incident re­sulted in several border clashes, because the Mon­gols, who were unfamiliar with smallpox, thought that the men had been poisoned by the Chinese.

Chinese contacts constituted the gravest danger from smallpox for the Mongols, who recognized that danger and did what they could to contain the dis­ease and prevent further contamination. It was cus­tomary strictly to avoid the stricken person, whether a parent, brother, wife, or child:

They provide [the sick] with a Chinese to take care of him; and if there is no Chinese available, they prepare his food and other necessities in a place other than their own and let the person stricken with smallpox take care of him­self....

For the Mongols the danger of exposure to small­pox and other diseases increased during the six­teenth century because of increasing contact with the Chinese. Not only did they encounter them dur­ing invasion raids and at the border markets and fairs, but also after midcentury many Chinese immi­grants settled north of the Great Wall and lived intermingled with the Mongols. These communities were particularly vulnerable to high mortality from epidemic diseases. One Chinese observer claimed that the border communities had grown to 100,000 by the 1590s, but “luckily” a great epidemic had cut their numbers down by half (Serruys 1980).

The Manchus, too, had increasing problems with the civilized diseases of China. In Manchuria, as in Mongolia, smallpox was a relatively rare disease. The widely scattered populations, often on the move, had prevented the virus from gaining a foothold. However, in the late Ming as Chinese began to settle in Manchnria and as contacts between Manchus and Chinese increased, the diseases of China - smallpox in particular - became a serious threat.

An observation relating to the year 1633, when the Manchu armies were ready to invade China, indicates their awareness of this threat: “Order beiles who have already once contracted smallpox to lead an army from I-p’ien-shih to take Shan-hai- kuan” (Serruys 1980). The order to pick only immu­nized troops for an extended stay in China shows that they understood the great risk of contracting smallpox there, and they knew that those who had once had the disease would not get it again.

Even after China was conquered by the Manchus, Ch’ing legislation for the Mongol bannermen indi­cates that the Manchu rulers continued to take the problem of smallpox seriously. Proscriptions against going to the capital when one had not been already infected with the disease were incorporated into the Ch’ing codes.

These examples illustrate the changes that took place in East Asia in the early modern period. There were real differences between the disease ecologies of the East and West, and these differences contin­ued to be important. Unlike Africa, the Americas, and many of the more sparsely settled countries of Europe, many density-dependent diseases were al­ready endemic in East Asia before the sixteenth century. Disease ecologies in the West were com­pletely transformed by the discovery of the New World. The high level of epidemic mortality in the early modem West may well be related to the un­usual disease exchange that took place between the urban centers of Europe and the peripheral primi­tive societies with relatively low-density popula­tions with which they came in contact.

No such transformation took place in East Asia. There was much greater stability in the high- density populations of China and Japan where many diseases were endemic and circulated regularly within a relatively closed system. Thus the arrival of the Europeans in the sixteenth century changed the disease ecology of East Asia very little.

The disease environment of early modem East Asia did change, but the reason for change was to­tally unrelated to new foreign contacts. In East Asia the dissemination of disease intensified because of population growth, increasing urbanization, an in­crease in the volume of trade within the region, and the integration of more sparsely populated frontier regions into the network of civilized diseases. This process was affected very little by outside develop­ments. In the modem period, however, when rapid transport began to connect all of the world regions, East Asia’s large, high-density population emerged as a disease center that could disseminate diseases to the rest of the world.

Ann Bowman Jannetta