1 Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Republic of Singapore.
2 Singapore Tuberculosis Control Unit, Tan Tock Seng Hospital, Singapore, Republic of Singapore.
3 Division of Cancer Control and Population Sciences, University of Pittsburgh Cancer Institute, and Department of Epidemiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania.
4 Duke-NUS Medical School, Singapore, Republic of Singapore.