[1] Univ Maryland, Sch Med, Dept Epidemiol & Prevent Med, Int Hlth Div, Baltimore, MD 20201 USA
[2] Natl Hepatol & Trop Med Res Inst, Cairo, Egypt
[3] Menoufia Univ, Natl Liver Inst, Shibin Al Kawm, Egypt
[4] NIAID, Infect Dis Lab, NIH, Bethesda, MD 20892 USA