Insufficient healthy Qi is the basis for disease. Pathogens trigger the occurrence of disease. Different pathogens cause different pathological changes, depending on the nature, severity, and region being attacked.
(1)Insufficient healthy Qi can be general, partial, constant, or temporary. Each insufficiency causes different reactions to pathogens. General insufficiency indicates vulnerability in all areas of the body. Partial insufficiency indicates vulnerability in some areas, although once the body is attacked in vulnerable areas the illness may spread to other areas. Constant insufficiency causes frequent illness, due to a naturally weak constitution. Temporary insufficiency indicates vulnerability when the body is weakened by fatigue, hunger, emotional stress, excessive sexual intercourse, etc.
(2)Huangdi Neijing states, “… with sufficient healthy Qi, pathogens will be unable to invade the body.” Conversely, if pathogens successfully invade, Qi in the body must be deficient. Theoretically, a person with insufficient healthy Qi will not have illness symptoms unless attacked by pathogens. But pathogens such as a chemical poison, an external injury (e.g. a gun wound), high temperature, or an electric shock can harm even those with abundant healthy Qi. Those with healthy Qi may be more resistant to an epidemic infection, but may still be infected.
(3)Particular pathogens may lead to particular diseases. For example, an abnormal climatic factor attack may precede that factor’s disease. A pathogenic dampness attack may precede dampness syndrome, a pathogenic heat attack may precede heat syndrome, a pathogenic cold attack may lead to cold syndrome, etc.
(4)The severity of the attack influences the pathogenic changes and the resulting disease. Generally, slight attacks result in mild diseases with a limited struggle between healthy Qi and pathogens. Serious attacks result in more serious diseases with a fierce struggle between healthy Qi and pathogens. For example, mild pathogenic wind attacks result in wind syndrome disease. Severe wind attacks may develop into cold syndrome.
(5)Attacks in different body regions result in different pathogenic changes. For example, a pathogenic cold attack on the Lungs may cause coughing and asthma, whereas in the stomach it may cause diarrhea and vomiting.