1. Institute of Population Health, University of Liverpool, Liverpool L69 3GF, UK
2. Real-Time Syndromic Surveillance Team, Field Services, Health Protection Operations, UK Health Security Agency, Birmingham B2 4BH, UK
3. National Institute for Health Research Health Protection Research Unit in Gastrointestinal Infections, University of Liverpool, Liverpool L69 7BE, UK
4. Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Wirral CH64 7TE, UK
5. Field Services North-West, Health Protection Operations, UK Health Security Agency, Liverpool L3 1DS, UK