1 Public Health England Field Service, Cambridge Institute of Public Health, Cambridge, United Kingdom.
2 Public Health England and Cambridge Universities Hospitals NHS Foundation Trust Cambridge, Cambridge, United Kingdom.
3 Statistics Unit, Statistics, Modelling and Economics Department, National Infection Service - Data and Analytical Sciences, Public Health England, London, United Kingdom.
4 National Infection Service, Public Health England, London, United Kingdom.
5 The authors are acknowledged at the end of the article.