[1] CDC Fdn, Ctr Dis Control & Prevent, Div Viral Dis, Atlanta, GA USA
[2] Ctr Dis Control & Prevent, Div Viral Dis, Atlanta, GA USA
[3] Bill & Melinda Gates Fdn, Enter & Diarrheal Dis Global Hlth, Seattle, WA USA
[4] Prince Wales Hosp, Dept Paediat, Hong Kong, Hong Kong, Peoples R China
[5] Johns Hopkins Univ, Int Hlth, Baltimore, MD USA