In terms of statistics of prescription use frequency, the Lung cleansing & detoxifying decoction was most frequently administered (78 times). This prescription is often used as the basic prescription in the Diagnosis and Treatment Protocol for Novel Coronavirus Pneumonia. Our hospital also takes it as the basic prescription, and obvious curative effect has been achieved. The Lung cleansing & detoxifying decoction is an optimized combination of several classic prescriptions (Ephedra, apricot kernel, gypsum, and licorice decoction (Maxing Shigan decoction), Belamcanda and ephedra decoction (Shegan Mahuang decoction), Minor bupleurum decoction (Xiaochaihu decoction) and Poria five powder (Wuling powder)) in Treatise on Febrile Diseases written by Zhang Zhongjing of Han Dynasty. All of them are designed against the pathogenesis of cold dryness and cold dampness. The combination of the prescriptions is reasonable and the nature and taste are gentle/flat ^[19]. The combination of all the herbs can achieve the functions of relieving heat and clearing the lung, dredging functional activity of Qi, promoting Qi transformation and disinhibiting water, repelling foulness and detoxification; the formula has been effective many times^[20,21]. Through network pharmacology, the researchers analyzed the mechanism of Lung cleansing & detoxifying decoction, and showed that this prescription mainly regulates MAPK1, MAPK3, MAPK8, MAPK14, IL-6 and other targets, and then regulates TNF, NF - κB and other signaling pathways to inhibit inflammatory reaction, regulate immune function, and reduce lung injury, so as to achieve the purpose of treating COVID-19 ^[22].

As for the attributes of TCM, the nature of majority of drugs against COVID-19 is warm/flat. The warm Chinese herbs have the functions of dispelling cold, supplementing deficiency, helping Yang, strengthening spleen and stomach, etc. They are suitable for cold constitution or cold/deficiency syndrome ^[23]. The epidemic situation in Wuhan is mainly cold and dampness, suggesting that the drug use is in line with the etiology. In the five flavors of medicine, the drugs with sweet taste were most frequently administered (2,196 times), which is followed by pungent taste, with the use frequency of 2,098 times. The "Plain Questions --- Great Theory of Yin, Yang, and Visceral Manifestation (Yin Yang Ying Xiang Da Lun)" has a record: "Pungent and sweet drugs are of divergence and supplement Yang, while sour and bitter drugs are of upwelling and discharging and strengthen Yin" ^[24]. "Grand Law (Hong Fan)" said: "Sour taste belongs to wood, bitter taste belongs to fire, sweet taste belongs to soil (earth), pungent taste belongs to gold, and salty taste belongs to water". Sweet taste can be tonic, harmonious, and slow; pungent taste can move and dissipate; these kinds of medicine can play the role of tonifying deficiency and Qi, improving the body's healthy Qi, strengthening and protecting Qi, and improving immunity. In the aspect of meridian tropism of drugs, lung meridian is prominent, and the main location of this epidemic is lung. TCM believes that the lung governs Qi and diffusion/downbearing. If the lung fails to do so, cough and wheezing will occur. Cold and evil Qi will enter from the exterior into the interior. The disease location is in the lung, with dry cough, sore throat, fatigue and other symptoms. The second most frequently used are the TCMs belonging to the spleen and stomach meridians. Dampness invades the spleen, causing diarrhea, vomiting, anorexia and other symptoms; this kind of medicine completely aims at the etiology and pathogenesis, which means to cultivate earth and generate metal. In the clinical symptoms, dry cough was most common, followed by fatigue and anorexia. The first symptoms of COVID-19 were mainly respiratory symptoms, accompanied by gastrointestinal symptoms. It is also consistent with the disease characteristics that "warm pathogen tends to attack the upper orifices, then firstly invades the lung" and the characteristics of "damp pathogen" in the epidemic febrile diseases. This is basically consistent with the NCP clinical characteristics published by Chen et al. ^[25]. The early symptoms and conditions of COVID-19 are not dangerous, but can suddenly aggravate, with rapid progress to the state of multiple organ failure, which should be paid attention to.

In the association rule analysis of high-frequency TCM, the top five are Pericarpium Citri Reticulatae---Poria cocos, Rhizoma Atractylodis Macrocephalae---Herba Pogostemonis, Radix Bupleuri---Radix Scutellariae, Rhizoma Atractylodis---Herba Pogostemonis, and Radix Codonopsis---Poria cocos; Pericarpium Citri Reticulatae and Poria cocos are often used to strengthen the spleen and remove dampness in the treatment of phlegm dampness trapped spleen. In this epidemic situation, many patients have gastrointestinal symptoms, in line with clinical medication. Radix Bupleuri plus Radix Scutellariae reconcile lesser Yang (Shao Yang), the former can relieve the external evil of half exterior and half interior, and the latter can clear away the internal heat of half exterior and half interior; the former upbears clear Yang, while the latter reduces turbid fire. Ascending clear and descending turbid, harmonizing exterior and interior, and harmonizing lesser Yang are achieved by their combination. Both Herba Pogostemonis andRhizoma Atractylodis are aromatic TCM; the former is pungent, and its nature is lukewarm(tepid), while the latter is pungent/bitter, and is warm in nature. The latter belongs to lung, spleen and stomach meridians. Rhizoma Atractylodis is the top grade product in Shennong's Classic of Materia Medica, which can remove dampness of spleen; it also has a strong Qi to stimulate the spleen Qi to rise. The combination of the two herbs can resolve the exterior with warmth and acridity, and diffuse and downbear Qi dynamic. Radix Codonopsis and Poria cocos are commonly used in strengthening the spleen and tonifying Qi, and are two components of Four Gentlemen decoction (most important TCM formula of tonifying Qi).高频中药进行关联规则分析，其中所得支持度排名前五的是（陈皮-茯苓）、（白术-藿香）、（柴胡-黄芩）、（苍术-藿香）、（党参-茯苓）；陈皮、茯苓常作为健脾祛湿的药治疗痰湿困脾，此次疫情中很多患者出现胃肠道症状，符合临床症状用药；柴胡配黄芩和解少阳，柴胡能解半表半里之外邪，黄芩能清半表半里之内热，柴胡升清阳，黄芩降浊火，升清降浊，调和表里，和解少阳；藿香和苍术均为芳香中药，藿香味辛，性微温；苍术味辛、苦，性温，归肺、脾、胃经，苍术为《神农本草经》上品，可化脾家之湿，兼雄壮之气而鼓动脾气升生，两者合用，辛温解表，宣降气机；党参、茯苓为健脾补气常用药，取四君子汤之义。