Epidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study.

<h4>Background</h4>While patterns of incidence of clinical influenza have been well described, much uncertainty remains over patterns of incidence of infection. The 2009 pandemic provided both the motivation and opportunity to investigate patterns of mild and asymptomatic infection using...

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Autores principales: Steven Riley, Kin O Kwok, Kendra M Wu, Danny Y Ning, Benjamin J Cowling, Joseph T Wu, Lai-Ming Ho, Thomas Tsang, Su-Vui Lo, Daniel K W Chu, Edward S K Ma, J S Malik Peiris
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Publicado: Public Library of Science (PLoS) 2011
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spelling oai:doaj.org-article:ef700bdbdf804b2596b1cf54d8e774b82021-11-18T05:41:47ZEpidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study.1549-12771549-167610.1371/journal.pmed.1000442https://doaj.org/article/ef700bdbdf804b2596b1cf54d8e774b82011-06-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21713000/?tool=EBIhttps://doaj.org/toc/1549-1277https://doaj.org/toc/1549-1676<h4>Background</h4>While patterns of incidence of clinical influenza have been well described, much uncertainty remains over patterns of incidence of infection. The 2009 pandemic provided both the motivation and opportunity to investigate patterns of mild and asymptomatic infection using serological techniques. However, to date, only broad epidemiological patterns have been defined, based on largely cross-sectional study designs with convenience sampling frameworks.<h4>Methods and findings</h4>We conducted a paired serological survey of a cohort of households in Hong Kong, recruited using random digit dialing, and gathered data on severe confirmed cases from the public hospital system (>90% inpatient days). Paired sera were obtained from 770 individuals, aged 3 to 103, along with detailed individual-level and household-level risk factors for infection. Also, we extrapolated beyond the period of our study using time series of severe cases and we simulated alternate study designs using epidemiological parameters obtained from our data. Rates of infection during the period of our study decreased substantially with age: for 3-19 years, the attack rate was 39% (31%-49%); 20-39 years, 8.9% (5.3%-14.7%); 40-59 years, 5.3% (3.5%-8.0%); and 60 years or older, 0.77% (0.18%-4.2%). We estimated parameters for a parsimonious model of infection in which a linear age term and the presence of a child in the household were used to predict the log odds of infection. Patterns of symptom reporting suggested that children experienced symptoms more often than adults. The overall rate of confirmed pandemic (H1N1) 2009 influenza (H1N1pdm) deaths was 7.6 (6.2-9.5) per 100,000 infections. However, there was substantial and progressive increase in deaths per 100,000 infections with increasing age from 0.66 (0.65-0.86) for 3-19 years up to 220 (50-4,000) for 60 years and older. Extrapolating beyond the period of our study using rates of severe disease, we estimated that 56% (43%-69%) of 3-19 year olds and 16% (13%-18%) of people overall were infected by the pandemic strain up to the end of January 2010. Using simulation, we found that, during 2009, larger cohorts with shorter follow-up times could have rapidly provided similar data to those presented here.<h4>Conclusions</h4>Should H1N1pdm evolve to be more infectious in older adults, average rates of severe disease per infection could be higher in future waves: measuring such changes in severity requires studies similar to that described here. The benefit of effective vaccination against H1N1pdm infection is likely to be substantial for older individuals. Revised pandemic influenza preparedness plans should include prospective serological cohort studies. Many individuals, of all ages, remained susceptible to H1N1pdm after the main 2009 wave in Hong Kong. Please see later in the article for the Editors' Summary.Steven RileyKin O KwokKendra M WuDanny Y NingBenjamin J CowlingJoseph T WuLai-Ming HoThomas TsangSu-Vui LoDaniel K W ChuEdward S K MaJ S Malik PeirisPublic Library of Science (PLoS)articleMedicineRENPLoS Medicine, Vol 8, Iss 6, p e1000442 (2011)
institution DOAJ
collection DOAJ
language EN
topic Medicine
R
spellingShingle Medicine
R
Steven Riley
Kin O Kwok
Kendra M Wu
Danny Y Ning
Benjamin J Cowling
Joseph T Wu
Lai-Ming Ho
Thomas Tsang
Su-Vui Lo
Daniel K W Chu
Edward S K Ma
J S Malik Peiris
Epidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study.
description <h4>Background</h4>While patterns of incidence of clinical influenza have been well described, much uncertainty remains over patterns of incidence of infection. The 2009 pandemic provided both the motivation and opportunity to investigate patterns of mild and asymptomatic infection using serological techniques. However, to date, only broad epidemiological patterns have been defined, based on largely cross-sectional study designs with convenience sampling frameworks.<h4>Methods and findings</h4>We conducted a paired serological survey of a cohort of households in Hong Kong, recruited using random digit dialing, and gathered data on severe confirmed cases from the public hospital system (>90% inpatient days). Paired sera were obtained from 770 individuals, aged 3 to 103, along with detailed individual-level and household-level risk factors for infection. Also, we extrapolated beyond the period of our study using time series of severe cases and we simulated alternate study designs using epidemiological parameters obtained from our data. Rates of infection during the period of our study decreased substantially with age: for 3-19 years, the attack rate was 39% (31%-49%); 20-39 years, 8.9% (5.3%-14.7%); 40-59 years, 5.3% (3.5%-8.0%); and 60 years or older, 0.77% (0.18%-4.2%). We estimated parameters for a parsimonious model of infection in which a linear age term and the presence of a child in the household were used to predict the log odds of infection. Patterns of symptom reporting suggested that children experienced symptoms more often than adults. The overall rate of confirmed pandemic (H1N1) 2009 influenza (H1N1pdm) deaths was 7.6 (6.2-9.5) per 100,000 infections. However, there was substantial and progressive increase in deaths per 100,000 infections with increasing age from 0.66 (0.65-0.86) for 3-19 years up to 220 (50-4,000) for 60 years and older. Extrapolating beyond the period of our study using rates of severe disease, we estimated that 56% (43%-69%) of 3-19 year olds and 16% (13%-18%) of people overall were infected by the pandemic strain up to the end of January 2010. Using simulation, we found that, during 2009, larger cohorts with shorter follow-up times could have rapidly provided similar data to those presented here.<h4>Conclusions</h4>Should H1N1pdm evolve to be more infectious in older adults, average rates of severe disease per infection could be higher in future waves: measuring such changes in severity requires studies similar to that described here. The benefit of effective vaccination against H1N1pdm infection is likely to be substantial for older individuals. Revised pandemic influenza preparedness plans should include prospective serological cohort studies. Many individuals, of all ages, remained susceptible to H1N1pdm after the main 2009 wave in Hong Kong. Please see later in the article for the Editors' Summary.
format article
author Steven Riley
Kin O Kwok
Kendra M Wu
Danny Y Ning
Benjamin J Cowling
Joseph T Wu
Lai-Ming Ho
Thomas Tsang
Su-Vui Lo
Daniel K W Chu
Edward S K Ma
J S Malik Peiris
author_facet Steven Riley
Kin O Kwok
Kendra M Wu
Danny Y Ning
Benjamin J Cowling
Joseph T Wu
Lai-Ming Ho
Thomas Tsang
Su-Vui Lo
Daniel K W Chu
Edward S K Ma
J S Malik Peiris
author_sort Steven Riley
title Epidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study.
title_short Epidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study.
title_full Epidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study.
title_fullStr Epidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study.
title_full_unstemmed Epidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study.
title_sort epidemiological characteristics of 2009 (h1n1) pandemic influenza based on paired sera from a longitudinal community cohort study.
publisher Public Library of Science (PLoS)
publishDate 2011
url https://doaj.org/article/ef700bdbdf804b2596b1cf54d8e774b8
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