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Article: Early epidemiological assessment of the virulence of emerging infectious diseases: A case study of an influenza pandemic

TitleEarly epidemiological assessment of the virulence of emerging infectious diseases: A case study of an influenza pandemic
Authors
KeywordsReferences (25) View In Table Layout
Issue Date2009
PublisherPublic Library of Science. The Journal's web site is located at http://www.plosone.org/home.action
Citation
Plos One, 2009, v. 4 n. 8 How to Cite?
AbstractBackground: The case fatality ratio (CFR), the ratio of deaths from an infectious disease to the number of cases, provides an assessment of virulence. Calculation of the ratio of the cumulative number of deaths to cases during the course of an epidemic tends to result in a biased CFR. The present study develops a simple method to obtain an unbiased estimate of confirmed CFR (cCFR), using only the confirmed cases as the denominator, at an early stage of epidemic, even when there have been only a few deaths. Methodology/Principal Findings: Our method adjusts the biased cCFR by a factor of underestimation which is informed by the time from symptom onset to death. We first examine the approach by analyzing an outbreak of severe acute respiratory syndrome in Hong Kong (2003) with known unbiased cCFR estimate, and then investigate published epidemiological datasets of novel swine-origin influenza A (H1N1) virus infection in the USA and Canada (2009). Because observation of a few deaths alone does not permit estimating the distribution of the time from onset to death, the uncertainty is addressed by means of sensitivity analysis. The maximum likelihood estimate of the unbiased cCFR for influenza may lie in the range of 0.16-4.48% within the assumed parameter space for a factor of underestimation. The estimates for influenza suggest that the virulence is comparable to the early estimate in Mexico. Even when there have been no deaths, our model permits estimating a conservative upper bound of the cCFR. Conclusions: Although one has to keep in mind that the cCFR for an entire population is vulnerable to its variations among sub-populations and underdiagnosis, our method is useful for assessing virulence at the early stage of an epidemic and for informing policy makers and the public. © 2009 Nishiura et al.
Persistent Identifierhttp://hdl.handle.net/10722/134206
ISSN
2015 Impact Factor: 3.057
2015 SCImago Journal Rankings: 1.395
PubMed Central ID
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorNishiura, Hen_HK
dc.contributor.authorKlinkenberg, Den_HK
dc.contributor.authorRoberts, Men_HK
dc.contributor.authorHeesterbeek, JAPen_HK
dc.date.accessioned2011-06-13T07:20:49Z-
dc.date.available2011-06-13T07:20:49Z-
dc.date.issued2009en_HK
dc.identifier.citationPlos One, 2009, v. 4 n. 8en_HK
dc.identifier.issn1932-6203en_HK
dc.identifier.urihttp://hdl.handle.net/10722/134206-
dc.description.abstractBackground: The case fatality ratio (CFR), the ratio of deaths from an infectious disease to the number of cases, provides an assessment of virulence. Calculation of the ratio of the cumulative number of deaths to cases during the course of an epidemic tends to result in a biased CFR. The present study develops a simple method to obtain an unbiased estimate of confirmed CFR (cCFR), using only the confirmed cases as the denominator, at an early stage of epidemic, even when there have been only a few deaths. Methodology/Principal Findings: Our method adjusts the biased cCFR by a factor of underestimation which is informed by the time from symptom onset to death. We first examine the approach by analyzing an outbreak of severe acute respiratory syndrome in Hong Kong (2003) with known unbiased cCFR estimate, and then investigate published epidemiological datasets of novel swine-origin influenza A (H1N1) virus infection in the USA and Canada (2009). Because observation of a few deaths alone does not permit estimating the distribution of the time from onset to death, the uncertainty is addressed by means of sensitivity analysis. The maximum likelihood estimate of the unbiased cCFR for influenza may lie in the range of 0.16-4.48% within the assumed parameter space for a factor of underestimation. The estimates for influenza suggest that the virulence is comparable to the early estimate in Mexico. Even when there have been no deaths, our model permits estimating a conservative upper bound of the cCFR. Conclusions: Although one has to keep in mind that the cCFR for an entire population is vulnerable to its variations among sub-populations and underdiagnosis, our method is useful for assessing virulence at the early stage of an epidemic and for informing policy makers and the public. © 2009 Nishiura et al.en_HK
dc.languageengen_US
dc.publisherPublic Library of Science. The Journal's web site is located at http://www.plosone.org/home.actionen_HK
dc.relation.ispartofPLoS ONEen_HK
dc.subjectReferences (25) View In Table Layouten_US
dc.titleEarly epidemiological assessment of the virulence of emerging infectious diseases: A case study of an influenza pandemicen_HK
dc.typeArticleen_HK
dc.identifier.emailNishiura, H:nishiura@hku.hken_HK
dc.identifier.authorityNishiura, H=rp01488en_HK
dc.description.naturepublished_or_final_versionen_US
dc.identifier.doi10.1371/journal.pone.0006852en_HK
dc.identifier.pmid19718434-
dc.identifier.pmcidPMC2729920-
dc.identifier.scopuseid_2-s2.0-69949146705en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-69949146705&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume4en_HK
dc.identifier.issue8en_HK
dc.identifier.isiWOS:000269415900021-
dc.publisher.placeUnited Statesen_HK
dc.identifier.scopusauthoridNishiura, H=7005501836en_HK
dc.identifier.scopusauthoridKlinkenberg, D=6603417925en_HK
dc.identifier.scopusauthoridRoberts, M=7404029879en_HK
dc.identifier.scopusauthoridHeesterbeek, JAP=6701820159en_HK
dc.identifier.citeulike5726548-

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