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Zhang Zhongjing believed that those who contracted cold pathogenic factors in winter and fell ill immediately were diagnosed with Shanghan (Cold Damage). Since the onset occurs upon initial infection, there is no accumulation of toxic qi within the body; although classified as Shanghan, the pathology is relatively mild. Zhang Zhongjing further stated: If the illness does not manifest immediately, the cold toxin hides within the skin and muscles (Fufu), transforming into Wenbing (Warm Disease) in spring and Rebing (Heat Disease) in summer. Having been injured by cold and subsequently infected by warmth, the two pathogens contend and merge into a single disease. This is akin to encountering a robber with accomplices aiding the evil; how can one withstand it? Therefore, injuries from cold in winter that do not manifest immediately but erupt in spring are more severe than direct Shanghan contracted in winter. Cases manifesting at the Summer Solstice occur because the cold toxin is shallow and located near the skin and pores; since the Healthy Qi (Zhengqi) can easily overcome it, it cannot remain long, thus manifesting quickly. If the toxin is slightly deeper, entering the muscles, the Healthy Qi cannot overcome it alone. It requires the warming Qi of spring to open and vent the pores before it can manifest, resulting in Wenbing. For cases where the toxin is particularly vigorous, after a long duration, it penetrates deeply into the bone marrow. Without the scorching heat of midsummer to dissipate it, the toxin cannot be activated. This explains why cold injury in winter leading to Heat Disease in summer is even more severe than Warm Disease. Thus, ancients stated that for winter cold injury, mild cases manifesting before the Summer Solstice are called Warm Disease, while severe cases manifesting after are called Shubing (Summerheat Disease). These three types share the same origin in Shanghan. The difference lies only in immediate versus delayed onset; following changes in pulse patterns, the clinical presentations become vastly different. Additionally, there are cases where one does not contract cold in winter but falls ill in spring due to abnormal Qi. These illnesses lack cold toxin as their root; although named Warm Disease, they are milder than those caused by winter cold injury followed by secondary warmth infection in spring. However, Spring Warmth and Winter Cold diseases are conditions contracted and caused by oneself. If a village, region, or family all suffer from the same illness simultaneously, this indicates that Warm Pathogens have transformed into Yi (Epidemic) diseases, which are not self-contracted from winter cold. Generally, when spring should be warm but is cold, summer hot but cool, autumn cool but hot, and winter cold but warm, the climate is abnormal. Those with strong constitutions contracting it will have mild symptoms, while those with weak constitutions will suffer severely. Hence, it is named Wenyi (Warm Epidemic), also known as Tianxing (Heavenly Transmission) or Shixing (Seasonal Transmission). If during a cold winter day, a specific area, village, or family all suffer from the same illness, this is also considered a seasonal Cold Epidemic. In general, cold injuries in winter that manifest after a period of time have cold toxin as their root. When combined with the contraction of abnormal Qi from the four seasons, the pathology inevitably becomes severe. Conditions such as Shanghan contracted in winter, Warm Qi diseases in spring, and seasonal Warm Epidemics, which manifest immediately upon infection and affect the exterior superficially, cannot be discussed on the same level as those involving the accumulation of cold toxin over time before manifestation. (From *Shanghan Wenyi Lun*)