■ Epidemic Qi
Epidemic Qi (lè qì) is a term that refers to a class of highly infectious and pathogenic exogenous disease evils. When there are abrupt changes in the natural environment, Epidemic Qi is prone to emergence and spread, leading to epidemic diseases.
In TCM literature, Epidemic Qi is also known as “epidemic toxin” (yì dú), “epidemic air” (yì qì), “abnormal Qi” (yì qì), “malignant Qi” (lì qì), “toxic Qi” (dú qì), and “perverse Qi” (guāi lì zhī qì). As noted in the Ming Dynasty text by Wu Youke, “On Warm Epidemics – Original Preface”: “The disease of plague is not caused by wind, cold, heat, or dampness, but rather by a different kind of abnormal Qi in the world.” This indicates that Epidemic Qi is a type of exogenous disease evil distinct from the Six Excesses (liù yín).
Epidemic Qi can be transmitted through the air, primarily invading the human body through the mouth and nose, but can also be contracted through contaminated food, insect bites, animal bites, skin contact, sexual contact, and blood transmission.
There are many types of Epidemic Qi, and the diseases they cause are collectively referred to as epidemic diseases (yì lè bìng), also known as epidemic illnesses (yì bìng) or plagues (wēn bìng). Examples include seasonal influenza, mumps (sāi yán), scarlet fever (làn hóu dān shā), diphtheria (bái hóu), tianhua (tiānhuā), epidemic dysentery (yì dú lì), typhoid fever (cháng shāng huǐ), cholera (huò luàn), plague (shǔ yì), epidemic hepatitis (yì huáng), as well as epidemic hemorrhagic fever, AIDS (AIDS), severe acute respiratory syndrome (SARS), avian influenza, and H1N1 influenza, all of which are infectious diseases caused by Epidemic Qi, including many modern clinical infectious diseases and virulent infections.
■ Nature and Pathogenic Characteristics of Epidemic Qi
1. Strong Infectiousness and Easy Spread
The primary pathogenic characteristic of Epidemic Qi is its strong infectiousness and tendency to spread. Epidemic Qi can be transmitted through various means such as air, food, and contact among people. Therefore, the history of contact with Epidemic Qi is an important basis for diagnosing epidemic diseases. In areas where Epidemic Qi is prevalent, regardless of age or physical condition, those who come into contact with it are likely to become ill. Epidemic Qi can cause widespread outbreaks as well as sporadic cases.
2. Sudden Onset and Severe Illness
Epidemic Qi is often associated with heat toxins, characterized by its violent nature, leading to rapid onset of illness, severe symptoms, and unpredictable changes in the disease course. Common symptoms include fever, agitation, bleeding, convulsions, and severe vomiting and diarrhea. The text “On Warm Epidemics” mentions that “those who are mildly affected may die by evening after falling ill in the morning, while those severely affected may die in an instant,” highlighting the dangerous nature of diseases caused by Epidemic Qi and their high mortality rate.
3. One Qi, One Disease, Similar Symptoms
Different types of Epidemic Qi have a certain specificity, leading to corresponding disease patterns in different organs. Each type of Epidemic Qi causes different diseases, each with its own clinical characteristics and transmission patterns, referred to as “one Qi causes one disease.” The same type of Epidemic Qi tends to target specific organs or meridians, resulting in similar symptoms among those affected by the same epidemic disease. For example, mumps typically presents with swelling in the parotid gland area. Epidemic dysentery usually manifests with high fever, severe abdominal pain, and urgent diarrhea with red and white pus in the stool.
■ Factors Influencing the Emergence of Epidemic Qi
There are various factors influencing the emergence of Epidemic Qi, primarily including climatic factors, environmental factors, preventive measures, and social factors.
★ Climatic Factors: Abnormal changes in natural climate, such as prolonged drought, extreme heat, flooding, and humid fog, can foster the emergence of Epidemic Qi and lead to epidemic diseases. For instance, the pandemics of cholera are related to such factors.
★ Environmental Factors: Poor environmental hygiene, such as water and air pollution, can also foster Epidemic Qi. Food contamination and improper diet can lead to the occurrence of epidemic diseases. For example, epidemic dysentery and epidemic hepatitis occur when Epidemic Qi enters the body through contaminated food. Geological disasters like earthquakes can also facilitate the spread of Epidemic Qi.
★ Inadequate Preventive Measures: Due to the strong infectiousness of Epidemic Qi, anyone who comes into contact with it can become ill. If preventive isolation is not properly implemented, it often leads to the occurrence or spread of epidemic diseases. Thus, “Songfeng’s Discussion on Epidemics” states: “Any household with an epidemic must not send clothing, food, or utensils to a household without an epidemic, nor should a household without an epidemic accept items from a household with an epidemic.”
★ Social Factors: Social factors can also influence the occurrence and spread of epidemic diseases. War, social unrest, poor working conditions, and extreme poverty can all lead to the emergence and spread of epidemics. Conversely, if a country is stable and pays attention to hygiene and epidemic prevention, implementing a series of effective preventive and therapeutic measures, Epidemic Qi can be effectively controlled.
