Mankind has suffered numerous plagues, some of which are particularly serious, which have a great impact on future generations: coronavirus pneumonia-19, SARS, plague, smallpox, influenza, cholera, malaria and so on. Generally speaking, plague is an infectious disease caused by some highly pathogenic substances, such as bacteria and viruses. It is generally caused by poor sanitary conditions after natural disasters.
Plague has long been recorded in China historical materials. For example, "Zhou Li Tianguan Notes" records: "People's diseases are raised by diseases, and they are always sick." "Lu Chunqiu Ji Chun Ji" records: "Ji Chun is prosperous in Xia Zhishi, and the people are ill." It shows that the knowledge of plague has reached a certain level at that time, and it is believed that plague can occur all year round. One of the reasons is that the seasonal qi is abnormal, which is caused by "untimely qi"