Study design and population

Details of the study design were published previously [23]. Briefly, 750 poultry-exposed individuals were enrolled from 5 rural Egyptian governorates and 250 unexposed control were enrolled from Cairo. A convenience sample of 150 individuals was selected in each rural site in the Nile Delta region (the governorates of Gharbiya, Sharkiya, Qalyubiya, and Kafr El Sheikh) and in Upper Egypt (Fayyoum governorate). At baseline and annually thereafter, a blood sample was obtained from each available participant and a baseline questionnaire was completed to assess demographic, health, and poultry exposure data. At base line, 565 sera from the exposed group and 150 from the control group were available for testing against H7. At follow up year 1, 682 and 139 subjects from each arm of the study were tested. At follow up year 2, we tested 649 poultry-exposed sera and 104 control sera. The study was approved by the Institutional Review Board (IRB) at St. Jude Children’s Research Hospital, Memphis TN, USA and by the Ethics Committee (EC) at the National Research Centre, Giza, Egypt. All subjects provided written informed consent on forms approved by the reviewing IRB and EC.