1. Infectious Diseases Translational Research Program, Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117545, Singapore
2. Research Office, National Centre for Infectious Diseases, Singapore 308442, Singapore
3. Department of Respiratory Sciences, University of Leicester, Leicester LE1 7RH, UK
4. Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, MD 20742, USA
5. Department of the Built Environment, College of Design and Engineering, National University of Singapore, Singapore 117356, Singapore