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J Infect Dis. 2015 Aug 15;212(4):562-9. doi: 10.1093/infdis/jiv109. Epub 2015 Feb 23.

A Systematic Review and Meta-Analysis of the Seroprevalence of Influenza A(H9N2) Infection Among Humans.

Author information

1
Department of Environmental and Global Health, College of Public Health and Health Professions Emerging Pathogens Institute, University of Florida, Gainesville.
2
Department of Environmental and Global Health, College of Public Health and Health Professions Emerging Pathogens Institute, University of Florida, Gainesville Division of Infectious Diseases, Global Health Institute, & Nicholas School of the Environment, Duke University, Durham, North Carolina Laboratory of One Health Research, Program in Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore.
3
Division of Infectious Diseases, Global Health Institute, & Nicholas School of the Environment, Duke University, Durham, North Carolina Laboratory of One Health Research, Program in Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore.

Abstract

INTRODUCTION:

Given that influenza A(H9N2) is recognized as a pandemic threat, we evaluated the overall burden of influenza A(H9N2) infections among avian-exposed human populations.

METHODS:

We performed a systematic search of PubMed, AGRICOLA, and CAB Abstracts databases for literature published during 1997-2013. Studies reporting serological evidence of human influenza A(H9N2) infection among avian-exposed populations were included. We used a World Health Organization (WHO)-recommended case definition for serological evidence of infection based on results of hemagglutination inhibition (HI) and microneutralization (MN) assays. We calculated overall seroprevalence through a random effects meta-analysis model.

RESULTS:

Seroprevalence data reported by the studies ranged from 1% to 43% (median, 9%) by HI, which was not significantly different from the seroprevalence estimated through the WHO-recommended case definition (median, 1.3%; range, 0.5%-42.6%). Reported seroprevalence by MN ranged from 0.6% to 9% (median, 2.7%), which was greater than the seroprevalence estimated through the WHO-recommended case definition (median, 0.3%; range, 0.1%-1.4%).

CONCLUSIONS:

A small proportion of avian-exposed humans had evidence of influenza A(H9N2) infection. As the virus has a near global distribution in poultry, it seems likely that present surveillance efforts are missing mild or asymptomatic infections among avian-exposed persons. It seems prudent to closely monitor avian-exposed populations for influenza A(H9N2) infection to provide prepandemic warnings.

KEYWORDS:

H9N2 subtype; hemagglutination inhibition test; influenza A virus; meta-analysis; microneutralization test; seroprevalence; systematic review

PMID:
25712969
PMCID:
PMC4598807
DOI:
10.1093/infdis/jiv109
[Indexed for MEDLINE]
Free PMC Article

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