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The syndrome of plague (Wenyi, infectious epidemic disease) has had established prescriptions by wise physicians throughout history. For instance, Zhang Zhongjing [Zhang Ji] utilized Da Qing Long Tang (Major Green Dragon Decoction), Yang Dan Tang (Yang Shield Decoction), Yue Bi Tang (Yue Bi Decoction), Huang Qin Tang (Scutellaria Decoction), Bai Hu Tang (White Tiger Decoction), Xiao Chai Hu Tang (Minor Bupleurum Decoction) and Da Chai Hu Tang (Major Bupleurum Decoction), San Cheng Qi Tang (Three Inheriting Qi Formulas: Tiao Wei Cheng Qi Tang, Xiao Cheng Qi Tang, Da Cheng Qi Tang), and Ma Huang Sheng Ma Tang (Ephedra and Citron Verbena Root Decoction). These clauses list the clinical manifestations of plague, employing sweating methods (Han Fa), purgative methods (Xia Fa), harmonizing methods (He Fa), and dual-resolving methods (Shuang Jie Fa), covering degrees of severity and depth with meticulous detail. However, these contents are scattered among the clauses of various meridians in the *Shanghan Lun* (Treatise on Cold Damage) without explicitly naming them as "plague." This is not because they did not wish to clarify it. The book was established upon the theory of cold damage, serving as a text distinguishing itself from cold damage, rather than a specialized treatise on plague. Moreover, ancient literary expressions were simple and concise; they emphasized pattern differentiation (Bian Zheng) over nomenclature. They intended for practitioners to differentiate carefully based on symptoms, so there was no need to distinguish by name, thereby naturally avoiding errors in confused treatment.

Subsequently, Liu Hejian authored *Xuan Ming Wu Qi Lun* (Discourse on Declaring the Five Qi), discussing plague in greater detail and establishing more comprehensive laws. Prescriptions such as Gui Ling Gan Lu Yin (Cassia Twig, Poria, and Sweet Dew Drink), Huang Lian Jie Du Tang (Coptis Decoction to Relieve Toxicity), San Yi Xiao Fang (Three Effective Formulas), Liang Ge San (Cool the Diaphragm Powder), Ren Shen Shi Gao Tang (Ginseng and Gypsum Decoction), and Shuang Jie San (Dual-Resolving Powder) are examples, yet none formally named the disease. Li Dongyuan (Li Gao) and Zhang Yishou (Zhang Yuansu, courtesy name Yilao) created Da Qiang Huo Tang (Major Notopterygium Decoction) and Jiu Wei Qiang Huo Tang (Nine-Ingredient Notopterygium Decoction), making their formulas even more comprehensive, but still lacking a dedicated book or specific title. It was not until Mr. Wu Youke integrated past and present knowledge with his personal insights that he wrote the *Wenyi Lun* (Treatise on Plague) regarding seasonal epidemics. His work can truly be described as pioneering a new path, shining like the sun and moon in the mid-sky.

Nevertheless, although his book exists, some contemporary scholars have either not seen it and thus do not use its methods, or have seen it but fail to believe in it; this is not surprising. There are those who recite his book with praise, yet when prescribing for specific conditions, they still largely disregard his methods. While verbally acknowledging it as a current epidemic syndrome, their hands continue to use formulas for cold damage, adhering strictly to cold damage methodologies—a phenomenon common everywhere. I speculate that their situation is certainly not one of knowing but refusing to use; rather, they know the name but have not mastered the method of pattern differentiation! Witnessing this with a pained heart, and disregarding my own ignorance and shallowness, I have selected Wu’s original text, adding annotations, revisions, deletions, or modifications. My intent is to distinguish the nature of plague from cold damage, particularly emphasizing careful differentiation at the initial stage of manifestation. Therefore, I added chapters at the beginning of the volume on differentiating Qi, complexion, pulse, tongue, and spirit (Shen/Essence-Spirit), enabling readers to understand clearly at a glance. Thus, Wu’s book can be used by everyone, reducing premature deaths from plague and increasing survival rates, which is indeed a blessing for the people of this era!

Dai Tianzhang, courtesy name Linjiao, from Shangyuan, recorded at Cun Cun Study Hall.
On the 15th day of the fifth month of summer, in the year Guimao (1783), respectfully inscribed by grandson Siqi.