Epidemiology and Infection

Influenza

Excess mortality associated with the 2009 pandemic of influenza A(H1N1) in Hong Kong

L. YANGa1, K. P. CHANa1, B. J. COWLINGa1, S. S. CHIUa2, K. H. CHANa3, J. S. M. PEIRISa3a4 and C. M. WONGa1 c1

a1 Department of Community Medicine, School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region, China

a2 Department of Paediatrics and Adolescent Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China

a3 Department of Microbiology, The University of Hong Kong, Hong Kong Special Administrative Region, China

a4 HKU Pasteur Research Centre, Hong Kong Special Administrative Region, China

SUMMARY

Reliable estimates of the burden of 2009 pandemic influenza A(pH1N1) cannot be easily obtained because only a small fraction of infections were confirmed by laboratory tests in a timely manner. In this study we developed a Poisson prediction modelling approach to estimate the excess mortality associated with pH1N1 in 2009 and seasonal influenza in 1998–2008 in the subtropical city Hong Kong. The results suggested that there were 127 all-cause excess deaths associated with pH1N1, including 115 with cardiovascular and respiratory disease, and 22 with pneumonia and influenza. The excess mortality rates associated with pH1N1 were highest in the population aged ≥65 years. The mortality burden of influenza during the whole of 2009 was comparable to those in the preceding ten inter-pandemic years. The estimates of excess deaths were more than twofold higher than the reported fatal cases with laboratory-confirmed pH1N1 infection.

(Accepted October 12 2011)

(Online publication November 11 2011)

Correspondence:

c1 Author for correspondence: Dr C. M. Wong, Department of Community Medicine and School of Public Health, The University of Hong Kong, 5/F William Mong Block, 21 Sassoon Road, Hong Kong. (Email: hrmrwcm@hkucc.hku.hk)

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