帝曰∶疟先寒而后热者，何也？岐伯曰∶夏伤于大暑，其汗大出，腠理开发，因遇夏气凄沧之水寒，藏于
腠理皮肤之中，秋伤于风，则病成矣。夫寒者，阴气也，风者，阳气也，先伤于寒，而后伤于风，故先寒而
后热也，病以时作，名曰寒疟。帝曰∶先热而后寒者，何也？岐伯曰∶此先伤于风，而后伤于寒，故先热而后
寒也，亦以时作，名曰温疟。其但热而不寒者，阴气先绝，阳气独发，则少气烦冤，手足热而欲呕，名曰瘅疟。
此明疟邪之由，各有不同，以暑热、水寒、风邪交混而成疟，其邪所伤有先后多寡不同，故发病亦异。如
夏伤暑热，汗出腠开，又遇水寒藏于腠理皮肤中，至秋又伤于风，则成疟。水寒为阴，风邪为阳，先伤水寒，
后伤风邪，故病发则先寒后热，名曰寒疟；如先伤风邪，后伤寒邪，故病发则先热后寒，名曰温疟；其有素来
阴虚阳盛之人，所伤之邪化热，而阴寒之气先绝，则阳邪独发，乃少气力而烦冤，手足皆热而欲呕，以火性炎
上故也，名曰瘅疟。由是观之，发于秋后者，多挟暑邪；发于春后者，必由风寒而无暑。或有挟湿者，其湿有
外感、内生之不同，脾虚则水液不化，而湿自内生；卫虚则表阳不固，而湿从外受。肝血少，风自内生；肾水
亏，热从内发。凡此诸义，皆当知者也。
The Yellow Emperor asked: What is the reason for malaria presenting with chills first and fever subsequently? Qibo replied: In summer, one is injured by severe heat (Shu-re), causing profuse sweating and the opening of Couli (pores and interstitial spaces). If one then encounters the cold water-cold energy of summer, this cold qi hides within the Couli and skin. When wind pathogen injures the body in autumn, the disease is formed. Cold belongs to Yin Qi, while wind belongs to Yang Qi. Since cold is injured first and wind subsequently, chills occur first followed by fever. The disease manifests at regular intervals and is named Cold Malaria (Han Nue).
The Yellow Emperor asked: What is the reason for presenting with fever first and chills subsequently? Qibo replied: This occurs when wind pathogen is injured first and cold pathogen subsequently, resulting in fever first and chills later. It also manifests at regular intervals and is named Warm Malaria (Wen Nue). If there is only fever without chills, it is because Yin Qi has been exhausted first, leaving Yang Qi to flare up independently. This results in shortness of breath, vexation and oppression, heat in the hands and feet, and a desire to vomit. This is named Dan Malaria (Dan Nue, a type of malaria characterized by fever without chills).
This clarifies that the origin of malaria pathogens varies. Malaria is formed by the mixing of Shu-heat, water-cold, and wind pathogen. Because the sequence and degree of pathogenic injury differ, the clinical manifestations vary. For instance, if one is injured by Shu-heat in summer, causing sweating and open Couli, and then water-cold hides within the Couli and skin, followed by wind pathogen injury in autumn, malaria forms. Water-cold is Yin, and wind pathogen is Yang. Injury to water-cold first and wind pathogen second leads to chills followed by fever upon manifestation, named Cold Malaria; injury to wind pathogen first and cold pathogen second leads to fever followed by chills, named Warm Malaria; in individuals with constitutive Yin deficiency and Yang excess, the injured pathogen transforms into heat, and the Yin-cold qi is exhausted first, causing Yang pathogen to flare up independently. This leads to weakness, vexation, heat in the extremities, and nausea, due to the nature of fire flaring upwards, named Dan Malaria.
From this perspective, malaria manifesting after autumn often involves Shu-pathogen; malaria manifesting after spring is necessarily caused by Wind-Cold without Shu. Some cases involve Dampness, which can be external or internal. Spleen deficiency leads to failure in transforming fluids, generating internal Dampness; Wei-Qi (Defensive Qi) deficiency leads to insecure exterior Yang, allowing external Dampness to invade. Liver Blood deficiency generates internal Wind; Kidney Water depletion generates internal Heat. All these principles should be understood.