title: Role of Food Handlers in Norovirus Outbreaks in London and South East England, 2013 to 2015.
abstract: Outbreaks caused by norovirus infection are common and occur throughout the year. Outbreaks can be related to food outlets either through a contaminated food source or an infected food handler. Both asymptomatic and symptomatic food handlers are potentially implicated in outbreaks, but evidence of transmission is limited. To understand potential food handler transmission in outbreak scenarios, epidemiological and microbiological data on possible and confirmed norovirus outbreaks reported in London and South East England in a 2-year period were reviewed. One hundred eighty-six outbreaks were associated with a food outlet or registered caterer in this period. These occurred throughout the year with peaks in quarter 1 of study years. A case series of 17 outbreaks investigated by the local field epidemiological service were evaluated further, representing more than 606 cases. In five outbreaks, symptomatic food handlers were tested and found positive for norovirus. In four outbreaks, symptomatic food handlers were not tested. Asymptomatic food handlers were tested in three outbreaks but positive for norovirus in one only. Environmental sampling did not identify the causative agent conclusively in any of the outbreaks included in this analysis. Food sampling identified norovirus in one outbreak. Recommendations from this study include for outbreak investigations to encourage testing of symptomatic food handlers and for food and environmental samples to be taken as soon as possible. In addition, sampling of asymptomatic food handlers should be considered when possible. However, in light of the complexity in conclusively identifying a source of infection, general measures to improve hand hygiene are recommended, with specific education among food handlers about the potential for foodborne pathogen transmission during asymptomatic infection, as well as reinforcing the importance of self-exclusion from food handling activities when symptomatic.
authors.affiliation: Field Epidemiology Service South East and London, Public Health England, 151 Buckingham Palace Road, London, SW1W 9SZ, UK.
authors.forename: C
authors.initials: C
authors.lastname: Rumble
authors.affiliation: North East and North Central London Health Protection Team, Public Health England, Ground Floor, South Wing, Fleetbank House, 2-6 Salisbury Square, London, EC4Y 8JX, UK.
authors.forename: S
authors.initials: S
authors.lastname: Addiman
authors.affiliation: Field Epidemiology Service South East and London, Public Health England, 151 Buckingham Palace Road, London, SW1W 9SZ, UK.
authors.forename: S
authors.initials: S
authors.lastname: Balasegaram
authors.affiliation: North East and North Central London Health Protection Team, Public Health England, Ground Floor, South Wing, Fleetbank House, 2-6 Salisbury Square, London, EC4Y 8JX, UK.
authors.forename: K
authors.initials: K
authors.lastname: Chima
authors.affiliation: London Public Health Laboratory, Public Health England, Public Health Laboratory London, 3rd Floor Pathology & Pharmacy Building, 80 Newark Street, London, E1 2ES, UK.
authors.forename: D
authors.initials: D
authors.lastname: Ready
authors.affiliation: City of London, Markets and Consumer Protection, Guildhall, London, EC2P 2EJ, UK.
authors.forename: J
authors.initials: J
authors.lastname: Heard
authors.affiliation: London Public Health Laboratory, Public Health England, Public Health Laboratory London, 3rd Floor Pathology & Pharmacy Building, 80 Newark Street, London, E1 2ES, UK.
authors.forename: E
authors.initials: E
authors.lastname: Alexander
mesh_terms: D017250:Caliciviridae Infections / Q000821:virology; D004196:Disease Outbreaks; D004739:England; D005511:Food Handling; D005759:Gastroenteritis / Q000453:epidemiology*; D006801:Humans; D008131:London; D029322:Norovirus
keywords: Asymptomatic infection; Food handlers; Norovirus; Symptomatic food handlers