1. Program in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore 169857, Singapore.
2. Viral Research and Experimental Medicine Centre, SingHealth Duke-NUS Academic Medical Centre, Singapore 169857, Singapore.
3. Saw Swee Hock School of Public Health, National University of Singapore, Singapore 117549, Singapore.
4. Department of Infectious Diseases, Singapore General Hospital, Singapore 169856, Singapore.