Li qi also known as Li gas, is one kind of evil gas of high infectivity in human body and belongs to pathological factors, which is different from the six climatic exopathogens. It is a substance naturally existed in nature and often attacks human body through noses and mouths.
The emerge and transmission are closely related to the climate, natural surroundings, food conditions and sanitation. This is often categorized into personal sickness as well as large scale of epidemic. The characteristics are rapidness, severity and high infectivity and quite easy to occur.
Common diseases are fulminant dysentery, diphtheria, infection with swollen head, cholera, smallpox and pestilence.