Ad Hoc Group on Foodborne Viral Infections meeting 26 April 2011

Summary of the third meeting of the ad hoc Group on Foodborne Viral Infections.

1. Introduction

At this meeting the group considered foodborne viruses: risks from shellfish, fresh produce and food handlers.

Having considered a revised scope of the risk assessment framework prior to the meeting, Members agreed to include reference to Hepatitis A, enterovirus, sapovirus, astrovirus and rotavirus in their risk assessment.

2. Foodborne viruses: risks from

Shellfish
Members received a presentation on work being undertaken by the Centre for Environment, Fisheries and Aquaculture Science (Cefas) as part of a 3 year FSA-funded project on the prevalence, distribution and levels of norovirus in oyster harvesting areas in the UK. Oysters from 39 sites in various parts of the UK had been sampled on a monthly basis. Norovirus in influent and effluent sewage at a treatment works in proximity to some harvesting sites was also measured. The study is due to complete in August 2011.

The study aims to determine the rates of positivity and levels of norovirus RNA in oysters, to assess seasonal and geographic variation, and to assess the relationship with E. coli and other risk factors. Members discussed the findings so far and asked to be updated on the final outcome of the study at a future meeting.

Fresh produce
Members received a presentation on the VITAL project concerning the acquisition of prevalence data in food supply chains. It began in April 2008 and was due to end in September 2011. The group discussed the findings so far and asked to be updated on the final outcome of the study, which will complete in September 2011, at a future meeting.

Food handlers
The HPA briefed Members on surveillance of general outbreaks of infectious gastro-intestinal disease. An outbreak was defined as an incident affecting at least 2 people from more than one household. The HPA collect informal reports on recognised outbreaks from Health Protection Units, clinical laboratories and Environmental Health Departments. Questionnaires are then sent out via the Consultant in Communicable Disease Control to collect further information.

Data showed that foodborne outbreaks declined over the surveillance period 1992 to 2010, because of the decline in those associated with Salmonella, such as S enteritidis and Clostridium perfringens. Outbreaks of norovirus in the years since 2000 associated with food have been very low although there was a large outbreak in 2009. Members were informed that surveillance of outbreaks of norovirus associated with food do not have very high ascertainment for various reasons: the illness is usually short-lived and fairly mild. Outbreaks linked to cohorts e.g. weddings, schools, are more likely to be detected rather than sporadic cases. It was also reported that the percentage of foodborne outbreaks of norovirus attributed to infected food handlers was greater than for other foodborne outbreaks.

Information presented to Members revealed that norovirus in foodborne outbreaks were mostly linked to molluscan shellfish, whereas in other foodborne outbreaks a smaller percentage of shellfish are implicated. As the question of availability of reliable data in other European countries was raised, the group discussed ideas on how surveillance could be improved.

3. Work Programme

The Group reviewed its work programme and agreed to invite:

  • Two Environmental Health Officers to attend a future meeting to brief them on how they prioritise and investigate norovirus
  • Cefas to give a presentation on sewage discharges and regulatory framework
  • FSA to invite a representative of Cleaner Seas Forum to discuss the role of the group
  • a representative from industry or VLA to give a presentation on Hepatitis E
  • HPA to give a presentation on human surveillance data and on proposals for improving surveillance