1. Immunology Programme, Life Sciences Institute and Department of Microbiology, National University of Singapore, Singapore 117456, Singapore.
2. Programme in Emerging Infectious Diseases, Duke-NUS Graduate Medical School, Singapore 169857, Singapore.
3. Institute of Infectious Diseases and Epidemiology, Communicable Disease Centre, Tan Tock Seng Hospital, Singapore 308433, Singapore.
4. Defense Medical and Environmental Research Institute, National Laboratories, Singapore 118230, Singapore.
5. Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore.
6. Singapore Institute for Clinical Sciences, Agency for Science, Technology and Research, Singapore 117609, Singapore.
7. Division of Infection and Immunity, University College of London, London WC1E 6BT, UK.