Treatise on Warm Epidemics (Wen Yi Lun) — The First Monograph on Infectious Diseases

Infectious diseases have caused great harm to humanity. Under certain external environmental conditions, they can spread among populations and cause epidemics. When an epidemic breaks out, it strikes rapidly, produces severe symptoms, affects large numbers of people, spreads over a wide area, and seriously endangers people's lives and health. In ancient China, infectious diseases broke out repeatedly, causing mass deaths. This was especially true during the Ming and Qing dynasties. According to some statistics, during the 276 years of the Ming Dynasty, there were 64 major epidemics, while during the 266 years of the Qing Dynasty, there were 74. This shows how frequently epidemics occurred. Physicians of successive dynasties attached great importance to the prevention and treatment of infectious diseases. For example, such famous medical classics as Huangdi Neijing (Yellow Emperor's Inner Classic), Shang Han Lun (Treatise on Cold Damage), Zhu Bing Yuan Hou Lun (Treatise on the Origins and Symptoms of Diseases), Qian Jin Fang (Essential Prescriptions Worth a Thousand Gold), and Wai Tai Mi Yao (Arcane Essentials from the Imperial Library) all contain recorded experience in preventing and treating infectious diseases, but these records are not systematic. The first specialized work in China on the treatment of acute infectious diseases is the Wen Yi Lun (Treatise on Warm Epidemics), written by Wu Youxing in the Qing Dynasty.

Wu Youxing, courtesy name Youke, was a native of Gusu (present-day Wu County, Jiangsu Province) in the late Ming Dynasty. Wu Youxing lived in an era of widespread epidemics. In 1641, in the late Ming Dynasty, when Wu Youxing was 49 years old, infectious diseases spread throughout Shandong, Zhejiang, Henan, Hebei, and other regions. At that time, many physicians could not find new treatment methods, so the therapeutic results were very poor. Wu Youxing personally witnessed the tragic scenes in areas struck by epidemics: “A lane of more than a hundred households, with not a single family left; a gate with dozens of people, with not a single survivor.” He assiduously studied medical principles, disregarded his own safety, went deep into epidemic areas, and carried out medical practice. Through detailed research on the epidemics prevailing at that time, combined with his own rich therapeutic experience, analysis, and summary, he finally completed the Wen Yi Lun in 1642, the 15th year of the Chongzhen reign.

The Wen Yi Lun put forward the view that the cause of what was then called “epidemic disease” (yi bing) was “the presence of an abnormal qi at a time when it should not be present.” The book held that cold damage and similar diseases were caused by contraction of the ordinary qi of heaven and earth, whereas epidemic diseases were caused by contraction of the “epidemic qi of heaven and earth.” The Wen Yi Lun distinguished warm epidemics from other heat diseases, thereby freeing the etiology of infectious diseases from the constraints of the previous “six qi” theory. For the first time in China, the Wen Yi Lun established a new viewpoint that the cause of disease was a weakened disease-fighting function of the body plus infection with virulent qi (li qi).

The Wen Yi Lun pointed out that the routes of infection of “virulent qi” were through air and contact, entering the body through the mouth and nose and causing disease. It also pointed out that virulent qi possesses specificity: only a particular type of virulent qi causes a corresponding infectious disease. The book also held that surgical diseases such as furuncles and carbuncles on the back were caused by infection with miscellaneous qi rather than by “fire.” For the first time, the Wen Yi Lun classified surgical infections and the causes of infectious diseases into the same category.

The Wen Yi Lun also attached great importance to the body’s resistance. The book held that “when the righteous qi is full, pathogenic factors cannot invade.” If the body’s resistance is strong, then even if there is the possibility of contact infection, the person will generally not fall ill. If “the original qi happens to be deficient, then in a single breath external pathogens will take advantage of the deficiency and invade.” If the body’s resistance is lowered and the person is exposed to infection, disease may then occur.

The Wen Yi Lun also proposed that the transmission routes of infectious diseases are “some are contracted from heaven, and some are transmitted by contact.” “Contracted from heaven” means airborne transmission, and “transmitted by contact” means contact transmission. Therefore, the book notes that “the mouth and nose of every person communicate with the qi of heaven” and “in a single breath external pathogens take advantage of the deficiency and invade.” The Wen Yi Lun held that the forms of infectious disease outbreaks could be either large-scale epidemics or scattered sporadic cases.

The Wen Yi Lun contains numerous highly scientific discussions on the source, cause, immunity, and epidemic nature of infectious diseases. Especially before the emergence of bacteriology in the mid-17th century, the Wen Yi Lun proposed: “The disease of warm epidemics is neither wind, nor cold, nor summer heat, nor dampness. It is contracted from a distinct abnormal qi that exists between heaven and earth.” This abnormal qi is precisely “virulent qi.” This theory was extremely advanced. The Wen Yi Lun’s discussion of immunity in warm epidemics is also truly admirable. The book says: “As for the invisible qi, it strikes certain animals specifically—such as cattle plague, sheep plague, chicken plague, and duck plague. How could it only affect humans? Yet cattle fall ill while sheep do not, chickens fall ill while ducks do not, and humans fall ill while birds and beasts do not. The harm differs because the qi differs.” This is indeed a brilliant exposition.

The Wen Yi Lun recorded many new methods for treating infectious diseases. For example, the book held that at the early stage of an infectious disease, it is appropriate to use Dayuan Yin (Reach the Membrane Source Decoction), and when the disease has deepened—that is, when the so-called “evil toxin attacks the stomach” stage is reached—one should not hesitate to “urgently purge in acute conditions.” These methods laid the foundation for the later treatment of infectious diseases.

The influence of the Wen Yi Lun on later generations was very great. A number of famous Qing Dynasty physicians, such as Dai Beishan, Yang Lishan, Liu Songfeng, Ye Tianshi, and Wu Jutong, all developed and innovated to varying degrees on the basis of the Wen Yi Lun. In the practice of fighting infectious diseases over the centuries, Chinese physicians created the doctrine of warm diseases (wen bing xue shuo). This doctrine originated in the Neijing, was nurtured in the Shang Han Lun, emerged during the Jin and Yuan dynasties, and matured during the Ming and Qing dynasties. In the development of the doctrine of warm diseases, the Wen Yi Lun, as China’s first monograph on the treatment of infectious diseases, made an enormous contribution. Even today, China applies the principles, methods, formulas, and medicinals of the doctrine of warm diseases to treat such infectious diseases as epidemic encephalitis B, influenza, measles, scarlet fever, and dysentery, achieving very good therapeutic results. In many respects, this is a continuation and development of the theories and experience of the Wen Yi Lun.