1. Mathematics Institute, University of Warwick , Coventry CV4 7AL , UK
2. School of Life Sciences, University of Warwick , Coventry CV4 7AL , UK
3. Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research (SBIDER), University of Warwick , Coventry CV4 7AL , UK
4. UK Health Security Agency , London NW9 5EQ , UK
5. Department of Statistics, University of Warwick , Coventry CV4 7AL , UK