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. 2010 Mar 25;5(3):e9880.
doi: 10.1371/journal.pone.0009880.

Estimating the disease burden of pandemic (H1N1) 2009 virus infection in Hunter New England, Northern New South Wales, Australia, 2009

Fatimah S Dawood  1 , Kirsty G Hope, David N Durrheim, Rodney Givney, Alicia M Fry, Craig B Dalton
Affiliations

Estimating the disease burden of pandemic (H1N1) 2009 virus infection in Hunter New England, Northern New South Wales, Australia, 2009

Fatimah S Dawood et al. PLoS One. .

Abstract

Introduction: On May 26, 2009, the first confirmed case of Pandemic (H1N1) 2009 virus (pH1N1) infection in Hunter New England (HNE), New South Wales (NSW), Australia (population 866,000) was identified. We used local surveillance data to estimate pH1N1-associated disease burden during the first wave of pH1N1 circulation in HNE.

Methods: Surveillance was established during June 1-August 30, 2009, for: 1) laboratory detection of pH1N1 at HNE and NSW laboratories, 2) pH1N1 community influenza-like illness (ILI) using an internet survey of HNE residents, and 3) pH1N1-associated hospitalizations and deaths using respiratory illness International Classification of Diseases 10 codes at 35 HNE hospitals and mandatory reporting of confirmed pH1N1-associated hospitalizations and deaths to the public health service. The proportion of pH1N1 positive specimens was applied to estimates of ILI, hospitalizations, and deaths to estimate disease burden.

Results: Of 34,177 specimens tested at NSW laboratories, 4,094 (12%) were pH1N1 positive. Of 1,881 specimens from patients evaluated in emergency departments and/or hospitalized, 524 (26%) were pH1N1 positive. The estimated number of persons with pH1N1-associated ILI in the HNE region was 53,383 (range 37,828-70,597) suggesting a 6.2% attack rate (range 4.4-8.2%). An estimated 509 pH1N1-associated hospitalizations (range 388-630) occurred (reported: 184), and up to 10 pH1N1-associated deaths (range 8-13) occurred (reported: 5). The estimated case hospitalization ratio was 1% and case fatality ratio was 0.02%.

Discussion: The first wave of pH1N1 activity in HNE resulted in symptomatic infection in a small proportion of the population, and the number of HNE pH1N1-associated hospitalizations and deaths is likely higher than officially reported.

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Conflict of interest statement

Competing Interests: Dave Durrheim is a member of the Strategic Advisory Group of Experts (SAGE) on Immunization to the Director General of the World Health Organization and provides advice on Pandemic H1N1 vaccine policy.

Figures

Figure 1
Figure 1. Community ILI, Hospitalizations, and Deaths Associated with Pandemic (H1N1) 2009 Virus Infection, Hunter New England, New South Wales, June 1-August 30, 2009.
Figure 2
Figure 2. Estimated Pandemic (H1N1) 2009 Disease Burden, Hunter New England, New South Wales, June 1-August 30, 2009.
See this image and copyright information in PMC

References

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