[The understanding of epidemic diseases in the Qin and Han Dynasties].

In the Qin and Han Dynasties, three views were argued as the main causes of epidemic diseases, the observation of climate, the interaction between nature and humans and 'witchcraft'. Specifically it was thought that abnormal climate, personnel and government decree, and 'gods' and 'ghosts' were responsible for epidemics. This perception led to corresponding countermeasures to deal with epidemic diseases. The abnormal climate in nature was believed to result in the occurrence of epidemic diseases. This was interpreted by traditional Chinese medicine in terms of exogenous diseases. For instance, Huang Di Nei Jing interpreted leprosy with the point of wind-pathogen attacking. Shang Han Lun treated epidemic diseases with the viewpoint of exogenous pathogen. The classic books of Chinese materia medica recorded many cases of preventing and treating epidemic diseases with materia medica. The personnel and government decree refers to the wrong decrees of Emperors and the poor implementation of officials. This was argued to lead to various disasters including epidemic diseases. It was interpreted by Dong Zhongshu, a famous Confucian in the Han Dynasty, as the punishment of gods upon their misconduct. This reminded emperors about reflecting on the epidemic diseases and correcting their mistakes politically. 'Gods' and 'ghosts' were also believed as the cause of epidemics. This idea drove people to deal with epidemic diseases through sacrifices and exorcism.