Objective To investigate the TCM syndrome characteristics of mild and severe influenza（ Flu）.Methods Adopted a multi-center epidemiological survey method to record the symptoms

physical and laboratory data of patients with mild

severe or critical influenza to analyze its clinical feature

main symptoms distribution

main symptoms duration and intensity

chest imaging results and syndrome differentiation of traditional Chinese medicine.Results Of the 975 cases of influenza patients

539 male

436 female

the average age 29 years old

550 were mild

344 were severe

and 81 were critically ill. During early stage after onset

mild or severe group showed exterior symptoms such as an aversion to cold

fever

cough

head and body pain

stuffy nose

runny nose

and these appear to be more prevalent in mild group; while fever

cough

panting

expectoration

headache and body aches and so on were overwhelmingly observed with respect to duration or intensity in the severe group. There were no blood aspect syndrome or death cases in mild and severe group. Among 81 cases in critically ill group

41 cases were with hemoptysis and spit pink blood

11 cases died. Conclusion the exterior wind-heat pattern

exterior wind-cold pattern

and heat-toxin assailing lung are the most common patterns of influenza. Critically ill cases may appear the condition of evil invading into the nutrient blood level. In mild cases

the lesions are in the defense level; while in the severe cases

the lesions are in the qi level

involving the lungs. For very rare cases

epidemic toxin directly injures nutrient blood

and reverse transmission to pericardium happens.