Epidemiological characteristics of H1N1 influenza in Lanzhou city,2009

Objective To analyze the epidemiological characteristics of H1N1 influenza in Lanzhou city,2009,and to provide scientific basis for formulating prevention and control measures.Methods The descriptive epidemiological method was used to analyze the data of H1N1 influenza collected from disease surveillance system for regional,time and population distribution.Results A total of 1 148 cases of H1N1 influenza were reported in Lanzhou city,2009,among whom,1 064 were laboratory confirmed cases and 84 clinically diagnosed cases.The incidence rate of H1N1 influenza was 35.16 per 100 000.There were 64 severe and critical cases and 12 dead cases reported.Twenty-four outbreaks of H1N1 influenza in schools involving 338 cases were reported during year 2009.The incidence peak was observed during mid-October and early November,involving 629 cases(54.79% of the total cases).The age-of-onset mainly ranged from 7 to 24 years(838 cases,accounting for 70.47% of all cases).The majority of the cases were students(809 cases,accounting for 70.47% of all cases).Conclusion Students are at the high risk of H1N1 influenza.H1N1 influenza vaccines should be given to the students and comprehensive measures should be adopted to control the outbreaks of this disease.