[1] Natl Univ Singapore, Saw Swee Hock Sch Publ Hlth, 12 Sci Dr 2,Tahir Fdn Bldg 10-01, Singapore 117549, Singapore
[2] Natl Univ Hlth Syst, 12 Sci Dr 2,Tahir Fdn Bldg 10-01, Singapore 117549, Singapore
[3] FHI 360, 359 Blackwell St 200, Durham, NC 27701 USA
[4] Tan Tock Seng Hosp, Dept Clin Epidemiol, Off Clin Epidemiol Analyt & Knowledge, Moulmein Rd, Singapore 308433, Singapore
[5] Tan Tock Seng Hosp, Dept Infect Dis, Natl Ctr Infect Dis, Moulmein Rd, Singapore 308433, Singapore
[6] Natl Skin Ctr, Dept STI Control DSC Clin, 31 Kelantan Ln,01-16, Singapore 200031, Singapore
[7] Natl Univ Singapore, Fac Law, Eu Tong Sen Bldg,469G Bukit Timah Rd, Singapore 259776, Singapore