title: Avian influenza A(H5N1) and A(H9N2) seroprevalence and risk factors for infection among Egyptians: a prospective, controlled seroepidemiological study.
abstract: 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.
authors.affiliation: Center of Excellence for Influenza Viruses.
authors.forename: Mokhtar R
authors.initials: MR
authors.lastname: Gomaa
authors.affiliation: Center of Excellence for Influenza Viruses.
authors.forename: Ahmed S
authors.initials: AS
authors.lastname: Kayed
authors.affiliation: Medical Research Division, National Research Center, Giza, Egypt.
authors.forename: Mona A
authors.initials: MA
authors.lastname: Elabd
authors.affiliation: Medical Research Division, National Research Center, Giza, Egypt.
authors.forename: Dina Abu
authors.initials: DA
authors.lastname: Zeid
authors.affiliation: Medical Research Division, National Research Center, Giza, Egypt.
authors.forename: Shaimaa A
authors.initials: SA
authors.lastname: Zaki
authors.affiliation: Medical Research Division, National Research Center, Giza, Egypt.
authors.forename: Amira S
authors.initials: AS
authors.lastname: El Rifay
authors.affiliation: Medical Research Division, National Research Center, Giza, Egypt.
authors.forename: Lobna S
authors.initials: LS
authors.lastname: Sherif
authors.affiliation: Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Pamela P
authors.initials: PP
authors.lastname: McKenzie
authors.affiliation: Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Webster
authors.affiliation: Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Webby
authors.affiliation: Center of Excellence for Influenza Viruses.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Ali
authors.affiliation: Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee.
authors.forename: Ghazi
authors.initials: G
authors.lastname: Kayali
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood; D002648:Child; D002675:Child, Preschool; D004534:Egypt / Q000453:epidemiology; D005260:Female; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000302:isolation & purification*; D053127:Influenza A Virus, H9N2 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000097:blood / Q000453:epidemiology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral
keywords: avian; cohort; epidemiology; influenza; seroprevalence