1 Epidemiology Unit, Department of Medicine, National University Health System, Singapore. 5 Lower Kent Ridge Rd, Singapore 119074, Singapore. Electronic address: hwang_ching_chan@nuhs.edu.sg.
2 Division of Infectious Diseases, Department of Medicine, National University Health System, Singapore. 5 Lower Kent Ridge Rd, Singapore 119074, Singapore.
3 Department of Laboratory Medicine, National University Health System, Singapore. 5 Lower Kent Ridge Rd, Singapore 119074, Singapore.
4 Division of Infectious Diseases, Department of Medicine, National University Health System, Singapore. 5 Lower Kent Ridge Rd, Singapore 119074, Singapore. Electronic address: somani_jyoti@nuhs.edu.sg.