Foodborne norovirus outbreak: the role of an asymptomatic food handler

Irene Barrabeig,Hortènsia Prellezo,Rosa Pintó,Rosa Bartolomé,Ariadna Rovira,Javier Buesa,Àngela Domínguez

doi:10.1186/1471-2334-10-269

Abstract

BackgroundIn July 2005 an outbreak of acute gastroenteritis occurred on a residential summer camp in the province of Barcelona (northeast of Spain). Forty-four people were affected among residents and employees. All of them had in common a meal at lunch time on 13 July (paella, round of beef and fruit). The aim of this study was to investigate a foodborne norovirus outbreak that occurred in the residential summer camp and in which the implication of a food handler was demonstrated by laboratory tests.MethodsA retrospective cohort study was designed. Personal or telephone interview was carried out to collect demographic, clinical and microbiological data of the exposed people, as well as food consumption in the suspected lunch. Food handlers of the mentioned summer camp were interviewed.Ten stool samples were requested from symptomatic exposed residents and the three food handlers that prepared the suspected food. Stools were tested for bacteries and noroviruses. Norovirus was detected using RT-PCR and sequence analysis.Attack rate, relative risks (RR) and its 95% confidence intervals (CI) were calculated to assess the association between food consumption and disease.ResultsThe global attack rate of the outbreak was 55%. The main symptoms were abdominal pain (90%), nausea (85%), vomiting (70%) and diarrhoea (42.5%). The disease remitted in 24-48 hours. Norovirus was detected in seven faecal samples, one of them was from an asymptomatic food handler who had not eaten the suspected food (round of beef), but cooked and served the lunch. Analysis of the two suspected foods isolated no pathogenic bacteria and detected no viruses. Molecular analysis showed that the viral strain was the same in ill patients and in the asymptomatic food handler (genotype GII.2 Melksham-like).ConclusionsIn outbreaks of foodborne disease, the search for viruses in affected patients and all food handlers, even in those that are asymptomatic, is essential. Health education of food handlers with respect to hand washing should be promoted.

Highlights

In July 2005 an outbreak of acute gastroenteritis occurred on a residential summer camp in the province of Barcelona
The virus can be excreted in the absence of symptoms [7], but incorrect manipulation by a food handler is necessary to produce an outbreak in which the food handler is involved
Of the 85 people exposed to lunch on 13 July 2005, 80 were interviewed: 67 children (5 children exposed could not be located), 8 monitors and 5 camp workers, including two of the food handlers (FH A and B)

Summary

Introduction

In July 2005 an outbreak of acute gastroenteritis occurred on a residential summer camp in the province of Barcelona (northeast of Spain). The aim of this study was to investigate a foodborne norovirus outbreak that occurred in the residential summer camp and in which the implication of a food handler was demonstrated by laboratory tests. The consumption of food contaminated by microorganisms is a common cause of gastroenteritis outbreaks in developed countries. A member of the Caliciviridae family, is considered the major cause of acute gastroenteritis in all. Foods may be contaminated by contact with human faecal matter at the source [6] or by unhygienic manipulation by a food handler excreting the virus [4], this second scenario is probably underestimated because it is difficult to prove [1]. The virus can be excreted in the absence of symptoms [7], but incorrect manipulation by a food handler is necessary to produce an outbreak in which the food handler is involved

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