[1] Natl Univ Singapore, Natl Univ Hlth Syst, Yong Loo Lin Sch Med, Dept Microbiol,Lab Mol RNA Virol & Antiviral Stra, Singapore 117597, Singapore
[2] ASTAR, Singapore Immunol Network, Singapore 138648, Singapore
[3] Coll Med, Minist Hlth, Communicable Dis Div, Natl Publ Hlth Lab, Singapore 169854, Singapore
[4] Natl Univ Singapore, Natl Univ Hlth Syst, Yong Loo Lin Sch Med, Dept Microbiol,Flavivirol Lab, Singapore 117597, Singapore