1. Field Epidemiology Services (Victoria), Public Health England, London, United Kingdom
2. These authors contributed equally
3. European Programme for Intervention Epidemiology (EPIET), European Centre for Disease Control (ECDC), Stockholm, Sweden
4. South West London Health Protection Team, Public Health England, London, United Kingdom
5. Commercial Environmental Health, London Borough of Richmond Upon Thames, London, United Kingdom
6. PHE Public Health Laboratory London, The Royal London Hospital, Barts Health NHS Trust, London, United Kingdom