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Wind-cold pathogenic qi converges inward from the exterior, and the disease typically emits no offensive odor to people; if an odor is present, it usually appears only after several days when transforming into Yangming Fu-organ syndrome (a syndrome characterized by heat accumulation in the stomach and intestines), manifesting merely as a putrid smell rather than a corpse-like smell.

Plague pathogenic qi steams outward from the interior; upon infection, an offensive odor immediately permeates the surroundings. Mildly, it fills the bed curtains; severely, it steams through the entire room. It specifically emits a corpse-like smell, not a putrid one. This is because the organs, Qi and blood, and body fluids of the human body become fragrant when receiving vital Qi, but become foul when receiving decaying Qi. Plague is a type of decaying Qi; once contracted by humans, it steams out from the internal organs to the muscle surface. The Qi and blood, and body fluids are steamed and decayed, leading to overflow. The degree of overflow varies in intensity, and the range of obstruction varies in distance. The Five Elements originally correspond to specific odors: Wood corresponds to fishy/foul smell (Sao), Metal to raw/fishy smell (Xing), Heart (Fire) to scorched smell (Jiao), Spleen to sweet/fragrant smell (Xiang), and Kidney to putrid smell (Fu). If the odor aligns with its proper elemental nature, it can be identified and named. However, plague is a miscellaneous Qi of Heaven and Earth; it is neither Sao, nor Xing, nor Jiao, nor Fu. Its odor upon contact is indescribable and cannot be distinguished unless one has a keen sense of smell. One can distinguish it by comparing the odor of a latrine with that of a corpse in a cursed place.

Once clearly distinguished, treatment will not be confused. Knowing it is plague and not Wind-cold means that for all exterior syndromes such as headache and fever, acrid-warm dispersing methods must not be mistakenly used; for various interior syndromes requiring clearing or purging, hesitation should be avoided.

Wind-cold governs convergence; convergence leads to tension, so the facial complexion often appears tight, smooth, and bright. Plague governs steaming and dispersion; dispersion leads to laxity, so the facial complexion often appears loose, slow, dirty, and dull. When affected by steaming Qi, body fluids overflow upward to the face, causing dirtiness and stagnation around the head and eyes, resembling grease or smoke stains, which look repulsive. These are all complexions of plague. Upon seeing this complexion, even if accompanied by headache and fever, acrid-hot dispersing methods should not be lightly employed. Upon seeing interior syndromes such as yellow tongue coating, irritability, and thirst, purgative methods should be applied immediately, without adhering to the saying that "purgation is never too late."

When Wind-cold is at the exterior, the tongue usually lacks a coating; if a white coating exists, it is thin and slippery. As it gradually transmits inward, it changes from white to yellow, from yellow to dry, and from dry to black. In plague, upon the appearance of headache and fever, a white coating appears on the tongue immediately, which is thick and not slippery; it may also have a pale yellow hue or appear coarse like accumulated powder. If the pathogen transmits to the Stomach, the coating may exhibit two or three colors, or remain white yet dry, or turn black yet remain non-dry. Generally, when epidemic pathogens enter the Stomach, the tongue coating resembles that of Wind-cold, but due to the presence of Dampness, it does not become dry. The key distinction during the exterior stage is that the tongue coating is white and thick, differing from Wind-cold. Correct identification during the exterior stage allows for avoiding acrid-warm dispersing methods, and applying cooling and purging methods during the interior stage, which constitutes the correct approach.