Avian Influenza A(H5N1) and A(H9N2) Seroprevalence and Risk Factors for Infection Among Egyptians: A Prospective, Controlled Seroepidemiological Study

• Published in: The Journal of infectious diseases Vol. 211; no. 9; pp. 1399 - 1407
• Main Authors: Gomaa, Mokhtar R., Kayed, Ahmed S., Elabd, Mona A., Zeid, Dina Abu, Zaki, Shaimaa A., El Rifay, Amira S., Sherif, Lobna S., McKenzie, Pamela P., Webster, Robert G., Webby, Richard J., Ali, Mohamed A., Kayali, Ghazi
• Format: Journal Article
• Language: English
• Published: United States Oxford University Press 01.05.2015
• Series: Editor's choice
• Subjects: Adolescent; Adult; Antibodies, Viral - blood; Child; Child, Preschool; Egypt - epidemiology; Female; Humans; Influenza A Virus, H5N1 Subtype - isolation & purification; Influenza A Virus, H9N2 Subtype - isolation & purification; Influenza, Human - blood; Influenza, Human - epidemiology; Influenza, Human - virology; Major and Brief Reports; Male; Middle Aged; Risk Factors; Seroepidemiologic Studies; VIRUSES; Young Adult; Egypt; Egypt, Arab Rep; influenza; seroprevalence; epidemiology; cohort; avian
• ISSN: 0022-1899; 1537-6613; 1537-6613
• DOI: 10.1093/infdis/jiu529

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 subdinical, and the case-fatality rate remain largely unanswered. Methods. We conducted a 3-year, prospective, controlled, seroepidemiological study that enrolled 750 poultryexposed 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.