The Wenyi Lun — China's Earliest Monograph on Infectious Diseases

Infectious diseases have inflicted great harm upon humanity. Under certain external environmental conditions, they can spread through populations and cause epidemics. When an infectious disease breaks out, its onset is rapid, its symptoms severe, the number of people affected is large, and the scope of its impact is extensive, seriously endangering the lives and health of the masses. In ancient China, infectious diseases broke out continuously, causing massive loss of life. This was especially true during the Ming and Qing dynasties. According to one statistical analysis, during the 276 years of the Ming dynasty, major epidemics broke out 64 times, while during the 266 years of the Qing dynasty, they broke out 74 times — a clear indication of their frequency. Successive generations of Chinese physicians attached great importance to the prevention and treatment of infectious diseases. Such renowned medical classics as the Huangdi Neijing, the Shang Han Lun, the Zhubing Yuanhou Lun, the Qianjin Fang, and the Waitai Miyao all contain records of experience in preventing and treating infectious diseases, but these records are not systematic. China's earliest specialized work on the treatment of acute infectious diseases is the Wenyi Lun (Treatise on Warm Epidemics), written by Wu Youxing in the Qing dynasty.

Wu Youxing, styled Youke, was a native of Gusu (present-day Wu County, Jiangsu Province) in the late Ming dynasty. The era in which Wu Youxing lived was precisely a period of widespread infectious disease epidemics. In 1641, during the late Ming, when Wu Youxing was forty-nine years old, epidemics spread throughout Shandong, Zhejiang, Henan, Hebei, and other regions. At that time, many physicians could find no new methods of treatment, and the results of treatment were consequently very poor. Wu Youxing witnessed with his own eyes the harrowing scenes in epidemic-stricken areas where "out of more than a hundred households in a single lane, not one remained intact; out of several dozen members of a single household, not a single survivor remained." He assiduously delved into medical principles, and disregarding his own safety, went deep into epidemic areas to conduct medical practice. Through detailed study of the epidemic diseases then rampant, combined with his own rich experience in treatment, and through analysis and synthesis, he finally completed the Wenyi Lun in the fifteenth year of the Chongzhen reign (1642).

The Wenyi Lun proposed that the cause of the diseases then termed "epidemic disease" was "the presence of qi that does not belong to that season." The Wenyi Lun held that diseases such as cold damage are caused by contracting the constant qi of heaven and earth, whereas "epidemic disease" is caused by "contracting the epidemic qi of heaven and earth." The Wenyi Lun thus distinguished "warm epidemics" from other febrile diseases, thereby breaking through the confines of the earlier "doctrine of the six pathogenic qi" regarding the causes of infectious diseases. For the first time in China, the Wenyi Lun established a new theory in which the cause of disease was defined as a combination of impaired disease-resistance function of the body and infection with pestilential qi (li qi).

The Wenyi Lun pointed out that the transmission route of "pestilential qi" is through the air and by contact, entering the body through the mouth and nose to cause disease. The Wenyi Lun also noted that pestilential qi possesses specificity — only a particular specific pestilential qi gives rise to the corresponding infectious disease. The book further held that surgical conditions such as deep-rooted furuncles and carbuncles of the back are caused by infection with miscellaneous qi, rather than by "fire." The Wenyi Lun was the first to place the etiology of surgical infections and epidemic diseases within the same category of causation.

The Wenyi Lun also placed great emphasis on the importance of the body's resistance. The book maintained: "When zheng qi is replete, pathogenic factors cannot invade." If the body's resistance is strong, then even if there is the possibility of contact transmission, disease is unlikely to develop. But if "the original qi happens to be in deficit, within the space of a single breath, external pathogens take advantage and invade" — that is, when the body's resistance is lowered and one is exposed to infection — then disease can occur.

The Wenyi Lun further proposed that the transmission routes of infectious diseases are "some contracted from heaven, some contracted by contagion." "Contracted from heaven" means airborne transmission, and "contracted by contagion" means contact transmission. Thus, the text notes: "The mouths and noses of all people communicate with the qi of heaven" and "within the space of a single breath, external pathogens take advantage and invade." The Wenyi Lun held that the mode of epidemic spread could be either pandemic or sporadic.

The Wenyi Lun contains a great wealth of highly scientific discussions concerning the sources and causes of infectious diseases, as well as their immunity and epidemic characteristics. It is particularly remarkable that as early as the mid-seventeenth century, before the advent of bacteriology, the Wenyi Lun proposed: "The disease of warm epidemics is neither wind, nor cold, nor summer heat, nor dampness, but is contracted from a distinct kind of abnormal qi existing between heaven and earth" — this abnormal qi being "pestilential qi" (li qi). This doctrine was extraordinarily advanced. The discussions on immunity to warm epidemics in the Wenyi Lun are also truly admirable. The book states: "As for this formless qi, it selectively strikes among animals — such as cattle plague, sheep plague, chicken plague, and duck plague. How could it be limited to human epidemics alone? Yet when cattle fall ill, sheep do not; when chickens fall ill, ducks do not; when humans fall ill, birds and beasts do not. When investigated, the harm to each is different because the qi differs for each." This is truly a passage of brilliant exposition.

The Wenyi Lun records many new methods for treating infectious diseases. For instance, the book holds that at the early stage of epidemic disease, Dayuan Yin (Reaching the Membrane Source Decoction) should be employed; and when the disease has progressed deeper, that is, when "pathogenic toxin assails the stomach," one should not hesitate to "attack an acute condition with urgent measures." These methods have all laid a foundation for the treatment of infectious diseases by later generations.

The Wenyi Lun exerted great influence on later times. A number of renowned Qing dynasty physicians — such as Dai Beishan, Yang Lishan, Liu Songfeng, Ye Tianshi, and Wu Jutong — all, to varying degrees, developed and creatively elaborated upon the foundations laid by the Wenyi Lun. Through their practice in struggling against infectious diseases, successive generations of Chinese physicians created the doctrine of warm diseases (wen bing xue). The doctrine of warm diseases has its source in the Neijing, was incubated within the Shang Han Lun, took form during the Jin and Yuan dynasties, and reached maturity in the Ming and Qing. In the developmental process of the warm disease doctrine, the Wenyi Lun, as China's first monograph on the treatment of infectious diseases, made an immense contribution. Even today, China applies the principles, methods, formulas, and medicinals of the warm disease doctrine to treat certain infectious diseases, such as epidemic Japanese B encephalitis, influenza, measles, scarlet fever, and dysentery, achieving very high rates of therapeutic success. In many of these applications, the theories and experience of the Wenyi Lun have been inherited and further developed.