From The Bird Flu: A Classical Perspective by Gabriel Weiss, 2007, p. 5.
In Section 1 of The Rites of Zhou 周禮 , “Offices of Heaven 天官冢宰” we read
Physicians treat the pathology of the ten-thousand people. All four seasons 四時 have their pestilences and epidemics 癘疾: spring has the disease of wasting-of-the-head 痟首疾, summer has the disease itching-sores 痒疥疾; fall has diseases of malarial fever cold 瘧寒疾; winter has the disease of coughing due to uprising qi 嗽上氣疾. By means of the five flavors, the five grains, and the five medicines, the diseases can be managed, and by means of the five different energies, the five sounds, and the five colors, whether the patient will live or die can be ascertained. Both treatment and diagnosis depend upon the changes of the nine orifices, and observation of the movements of the nine storehouses. As for diseases of the people, one should first categorize analytically, and then treat. Should the case end in death, each method employed should be recorded and submitted to the Official Physician. 
In this passage, the four seasons are immediately correlated with different categories of disease, without seeking to explain any causal relationship. The quality of the illness or epidemic is, however, related to the season in which it appears.
 Where a question-mark appears in the body of Chinese text, it indicates that the source material was missing a character at that point in the text.
 Unless otherwise indicated, all translation is my own.