Estimate of 2009 H1N1 influenza cases in Shenzhen – the biggest migratory city in China

Xiongwei Xie(Shenzhen Center for Disease Control and Prevention), Shaoyou Lu(Shenzhen Center for Disease Control and Prevention), Jinquan Cheng(Shenzhen Center for Disease Control and Prevention), Xin Cheng(Shenzhen Center for Disease Control and Prevention), Zimeng Xu, Jin Mou(Shenzhen Center for Disease Control and Prevention), Shujiang Mei(Shenzhen Center for Disease Control and Prevention), Dong-Sung Kong(Shenzhen Center for Disease Control and Prevention), Xiang Wang(Shenzhen Center for Disease Control and Prevention), Y. LI(Shenzhen Center for Disease Control and Prevention), Gracia Fellmeth, Peter W. Hellings(Shenzhen Center for Disease Control and Prevention)
Epidemiology and Infection
July 12, 2011
10.1017/s0950268811001312
Cited by 5Open Access
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Abstract

The 2009 novel H1N1 influenza pandemic had a significant impact on Shenzhen's population with 2063 laboratory-confirmed human H1N1 cases and five deaths being reported. We used parameters from two population-based surveys and the Shenzhen Influenza Surveillance System to estimate the total number of H1N1 influenza infections in Shenzhen in the 2009 pandemic. The attack rate of influenza-like illness (ILI) in family households was 11·2% (95% CI 9·4-13·0), with 80·2% (95% CI 77·8-82·5) seeking medical care. The ILI attack rate in workers was 38·1% (95% CI 34·3-41·7) with 72·5% (95% CI 66·9-78·0) seeking medical care. The average H1N1 positive rate in individuals reporting ILI and testing by polymerase chain reaction was 22·7%. A total of 611 000-768 000 people, or 4·7-5·9% of the Shenzhen population, are estimated to have experienced H1N1 influenza. The estimated total number of cases of H1N1 is likely to be 330 times greater than the number of laboratory-confirmed cases.

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