Journal
JOURNAL OF INFECTIOUS DISEASES
Volume 211, Issue 9, Pages 1399-1407Publisher
OXFORD UNIV PRESS INC
DOI: 10.1093/infdis/jiu529
Keywords
influenza; avian; epidemiology; seroprevalence; cohort
Categories
Funding
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, US Department of Health and Human Services [HHSN266200700005C]
- American Lebanese Syrian Associated Charities
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Background. A(H5N1) and A(H9N2) avian influenza viruses are enzootic in Egyptian poultry, and most A (H5N1) human cases since 2009 have occurred in Egypt. Our understanding of the epidemiology of avian viruses in humans remains limited. Questions about the frequency of infection, the proportion of infections that are mild or subclinical, and the case-fatality rate remain largely unanswered. Methods. We conducted a 3-year, prospective, controlled, seroepidemiological study that enrolled 750 poultry-exposed and 250 unexposed individuals in Egypt. Results. At baseline, the seroprevalence of anti-A(H5N1) antibodies (titer, >= 80) among exposed individuals was 2% significantly higher than that among the controls (0%). Having chronic lung disease was a significant risk factor for infection. Antibodies against A(H9N2) were not detected at baseline when A(H9N2) was not circulating in poultry. At follow-up, A(H9N2) was detected in poultry, and consequently, the seroprevalence among exposed humans was between 5.6% and 7.5%. Vaccination of poultry, older age, and exposure to ducks were risk factors for A(H9N2) infection. Conclusions. Results of this study indicate that the number of humans infected with avian influenza viruses is much larger than the number of reported confirmed cases. In an area where these viruses are enzootic in the poultry, human exposure to and infection with avian influenza becomes more common.
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