[Epidemiological characteristics of 420 influenza A (H1N1) cases confirmed in the early stage of the epidemic in mainland China].
OBJECTIVE
To describe the epidemical characteristics of A (H1N1) influenza identified in the early stage (from May 11 to June 22, 2009) of the epidemic, in mainland China.


METHODS
Epidemical characteristics of 420 confirmed A (H1N1) influenza cases reported from May 11 to June 22, 2009 were analyzed descriptively, including the distribution of age, sex, source of infection, main symptoms and incubation period.


RESULTS
A total of 77.8% early cases in mainland China were imported from other countries. Three countries including America, Canada and Australia were attributed to 90% of the imported cases. Most of the cases were from 6 months to 73 years old, with 94% of them under 50 years. Most of the symptoms would include fever (81%), cough (40%) and sore throat (35%). The mean incubation period of second-generation cases was 4.3 (4.2 +/- 1.5) days.


CONCLUSIONS
Imported cases dominated the total cases in the early stage of the epidemic had similar gender distribution of those from exporting countries. Fever, cough and sore throat were the three main symptoms manifested in influenza cases. 2.5 +/- 1.9 (1 - 11) days was found in imported cases between the day of off-board and the onset of symptoms. The incubation period was 4.3 +/- 1.7 (1 - 8) days among the secondary cases.
Li
Ya-pin
YP
State Key Laboratory of Pathogen and Biosecurity, Academy of Military Medical Science Institute of Microbiology and Epidemiology, Beijing 100071, China.
Qian
Quan
Q
Fang
Li-qun
LQ
Yang
Hong
H
Wei
Mao-ti
MT
Gao
Yan
Y
Yang
Hua
H
Zhang
Yong
Y
Cao
Wu-chun
WC
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology* / Q000821:virology; D008297:Male; D008875:Middle Aged; D055815:Young Adult