Epidemic and control of pandemic influenza A (H1N1) in Tianjin municipality, 2009

Objective To analyze the epidemiological characteristics of pandemic influenza A (H1N1) epidemic and evaluate the control measures in Tianjin in 2009. Methods The control effects of field response time and school closure were evaluated for 18 influenza A (H1N1) outbreaks in the communities in Tianjin. Results A total of 1498 influenza like illness cases were reported, the average attack rate was 2.12%. The median of the intervals between the onset of the first case and reporting was 5 days. The median of the outbreak durations was 12.5 days. The median of the attack rates at the first field response was 1.17%. The median of the outbreak durations after response was 6 days. The attack rate at the first response were positively correlated with the overall attack rate (r=0.77, P=0.000). If the response was taken when the attack rate in schools was 0.1%, the overall attack rate was lower than that when the attack rate in schools was 0.1% (P=0.000). The difference on the overall attack rate had no statistical significance when the school closure was taken if the attack rate was 0.1% or 0.1%. Conclusion Early reporting of the outbreak in school is the key to control pandemic influenza A (H1N1). When pandemic influenza A (H1N1) widely affects communities, it is necessary to take comprehensive control measures, such as case isolation and room ventilation.