1 Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
2 Department of Infectious Diseases, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Hills Road, Cambridge CB2 0QQ, United Kingdom.
3 Clinical Microbiology and Public Health Laboratory, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge CB2 0QW, United Kingdom.
4 Department of Public Health and Primary Care, University of Cambridge, Institute of Public Health, Forvie Site, Cambridge Biomedical Campus, Cambridge CB2 0SR, United Kingdom.
5 Air Force Medical University, 169 Changle West Road, Xi'an, Shaanxi 710032, PR China.