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Has estimation of numbers of cases of pandemic influenza H1N1 in England in 2009 provided a useful measure of the occurrence of disease?

Has estimation of numbers of cases of pandemic influenza H1N1 in England in 2009 provided a useful measure of the occurrence of disease?
Has estimation of numbers of cases of pandemic influenza H1N1 in England in 2009 provided a useful measure of the occurrence of disease?
BACKGROUND: Surveillance indicators of influenza activity have generally provided robust comparative trend data for England. These indicators became less reliable, however, for monitoring trends in activity, or comparisons with previous years, during the influenza pandemic in 2009 because of changes in the perception of risk and changes in the systems of healthcare delivery. An approach was developed to estimate the number of cases of influenza-like illness (ILI) occurring because of infection with pandemic influenza virus. METHODS AND FINDINGS: The number of cases was estimated each week in England on the basis of total number of patients consulting healthcare services with ILI; estimates of the proportion of individuals in the community experiencing an ILI-seeking health care; and the proportion of these positive on laboratory testing. Almost 800,000 cases (range 375,000-1.6 million) of symptomatic ILI cases were estimated to have occurred over the course of the two waves of pandemic activity in England. More cases were estimated to have occurred in the second wave than in the first. CONCLUSIONS: These results underestimate the total number of infections as they do not include asymptomatic infections nor those with mild illness not meeting the definition of a case of ILI. Nevertheless, the case number estimates provide a useful indicator of the trend in influenza activity and weekly data were extensively used in media reports. Although surveillance methods differ between countries, the approach of synthesising available data sources to produce an overall estimate of case numbers could be applied more widely to provide comparative data.
case number estimation, England, pandemic influenza
1750-2640
e504-e512
Evans, Barry
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Charlett, Andre
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Powers, Cassandra
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McLean, Estelle
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Hongxin, Zhao
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Bermingham, Alison
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Smith, Gillian
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Wreghitt, Tim
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Andrews, Nick
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Pebody, Richard
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Watson, John M.
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Evans, Barry
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Charlett, Andre
68f80073-88b5-4193-8224-1172d58f2bbf
Powers, Cassandra
b8f0a12a-d192-469a-b95c-7ddd164dc8ea
McLean, Estelle
d26a1af6-e8d1-41dc-a72d-5518c6550592
Hongxin, Zhao
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Bermingham, Alison
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Smith, Gillian
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Wreghitt, Tim
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Andrews, Nick
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Pebody, Richard
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Watson, John M.
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Evans, Barry, Charlett, Andre, Powers, Cassandra, McLean, Estelle, Hongxin, Zhao, Bermingham, Alison, Smith, Gillian, Wreghitt, Tim, Andrews, Nick, Pebody, Richard and Watson, John M. (2011) Has estimation of numbers of cases of pandemic influenza H1N1 in England in 2009 provided a useful measure of the occurrence of disease? Influenza and Other Respiratory Viruses, 5 (6), e504-e512. (doi:10.1111/j.1750-2659.2011.00259.x). (PMID:21668667)

Record type: Article

Abstract

BACKGROUND: Surveillance indicators of influenza activity have generally provided robust comparative trend data for England. These indicators became less reliable, however, for monitoring trends in activity, or comparisons with previous years, during the influenza pandemic in 2009 because of changes in the perception of risk and changes in the systems of healthcare delivery. An approach was developed to estimate the number of cases of influenza-like illness (ILI) occurring because of infection with pandemic influenza virus. METHODS AND FINDINGS: The number of cases was estimated each week in England on the basis of total number of patients consulting healthcare services with ILI; estimates of the proportion of individuals in the community experiencing an ILI-seeking health care; and the proportion of these positive on laboratory testing. Almost 800,000 cases (range 375,000-1.6 million) of symptomatic ILI cases were estimated to have occurred over the course of the two waves of pandemic activity in England. More cases were estimated to have occurred in the second wave than in the first. CONCLUSIONS: These results underestimate the total number of infections as they do not include asymptomatic infections nor those with mild illness not meeting the definition of a case of ILI. Nevertheless, the case number estimates provide a useful indicator of the trend in influenza activity and weekly data were extensively used in media reports. Although surveillance methods differ between countries, the approach of synthesising available data sources to produce an overall estimate of case numbers could be applied more widely to provide comparative data.

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Published date: June 2011
Keywords: case number estimation, England, pandemic influenza
Organisations: Faculty of Health Sciences

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Local EPrints ID: 351003
URI: http://eprints.soton.ac.uk/id/eprint/351003
ISSN: 1750-2640
PURE UUID: 29086af0-bd3c-429e-8538-e4c0ec436e59

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Date deposited: 12 Apr 2013 13:24
Last modified: 14 Mar 2024 13:34

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Contributors

Author: Barry Evans
Author: Andre Charlett
Author: Cassandra Powers
Author: Estelle McLean
Author: Zhao Hongxin
Author: Alison Bermingham
Author: Gillian Smith
Author: Tim Wreghitt
Author: Nick Andrews
Author: Richard Pebody
Author: John M. Watson

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