Cycles of high fevers and shivering chills were understood as a seasonal phenomena related to weather patterns in Chinese medicine. The Chou Li--Record of Institutions of the Chou Dynasty, a text from the early Han DynastyÑdescribes this pattern: "Each of the four seasons has its characteristic epidemics (li chi). In spring there comes feverish aches and headaches (Hsiao shou chi); in summer there are 'itching scabies-like epidemics' (yang chieh chi); in autumn there are malarial and other fevers (nio han chi); in winter there are respiratory diseases (sou shang chhi chi)."

The experience of chills and fevers was associated with several types of illness, and a person in China knew that it was likely to occur in the autumn. The experience of chills and fevers was marked by alternating periods of shivering cold and sweltering heat. The patient would first be treated at home, and if the illness were not cured, a doctor would be called to the house. The diagnosis of the illness would reveal that it was caused by a blocked flow (xun) of ch'i resulting from imbalances of yin and yang. The primary treatment to restore the proper flow was acupuncture, which would return the yin and yang to their proper domains, allowing a return to the proper flow of ch'i. In addition to receiving acupuncture, the patient might also take pharmaceuticals from local plants in an attempt to relieve the symptoms.

A good description of these symptoms and the underlying causes of this illness appears in the Huang-ti nei-ching:

The Yellow Emperor said: "All intermittent fevers are caused by wind, and they have (specific) periods of dormancy and outbreak. Why is this so?"

Chi'i Po replied: "At the beginning of the development of a yao-illness, the (patient's) fine hair rises; he will stretch out (his four limbs) and yawn. Then an outbreak occurs. (The patient suffers from a feeling of) cold that causes him to tremble and his jaws to chatter. His waist and his back ache both alike. As soon as these chills diminish (the patient) feels heat in both the internal and external (regions of his body). His head aches as if it were about to burst; he is thirsty and yearns for something cold to drink."

The Yellow Emperor asked: "Which influences cause these (symptoms)? I should like to hear about the (underlying) principle."

Ch'i Po said: "(The underlying principle of this illness may be seen in) the mutual contest of yin and yang (influences), as they cause each other depletions and repletions, and as they move into each otherÕs (territory). When yang (influences) enter the yin (conduits), a repletion emerges in the yin (conduits), while a depletion occurs in the yang (conduits). If a depletion strikes the yang-brilliance (conduit, the patient will suffer from) cold that causes him to tremble, and his jaws to chatter. If the great-yang (conduit) is depleted, pain is felt in the waist, the back, the head, and the neck. If all three yang (conduits) are affected simultaneously by a depletion (of influences), the yin influences will be in excess. If the yin influences are in excess, cold develops in the bones, accompanied by pain. Cold is generated inside (the body) with the result that both (the bodyÕs) center and its external (areas) all suffer from cold. In case of an excess of yang (influences), external heat develops; in case of a depletion of yin (influences), external heat develops; in case of depletion of yin (influences), internal heat develops. If (the body) suffers from heat both internally and externally, panting and thirst result, and (the patient) yearns for cold drinks. All such (illnesses) are caught in summer as harm caused by heat. An abundance of heat influences is stored inside the skin and outside of the intestines and the stomach. This is the area where the (body's) constructive influences reside. As a result of this (condition), the openings through which perspiration leaves relax (their tight closure), and the pores open, and one is affected by the influences of autumn, in that sweat leaves (the body) and meets with wind, or one gets (the illness) while bathing. Water influences settle inside the skin, and reside together with one's protective influences. The protective influences, however, move through the yang (conduits) during the day-time and through the yin (conduits) during night. Here now, the (evil) influences will be able to (follow the protective influences into) the yang (conduits) and move outwards to the external (areas of the body), and they will be able to get access to the yin (conduits) and extend into the internal (areas of the body). Because the (evil influences) reach into the internal and into the external (areas of the body), daily outbreaks (of the illness) occur."

The Yellow Emperor said: "What is the reason when the outbreaks occur only every other day?"

Ch'i Po said: ÒThe (evil) influences reside deep (in the body); internally they reach into the yin (areas of the body). Only the yang influences emerge; the yin (influences) and the evil (influences) remain in the interior. The contest between yin and yang (influences) does not permit (the evil influences) to emerge (at all times). Thus (the illness) breaks out only every other day."