INTERNATIONAL EPIDEMIOLOGIC AND MICROBIOLOGICAL STUDY OF OUTBREAK OF SALMONELLA-AGONA INFECTION FROM A READY-TO-EAT SAVOURY SNACK .1. ENGLAND AND WALES AND THE UNITED-STATES

Objectives-To identify the source of an international outbreak of food poisoning due to Salmonella agona phage type 15 and to measure how lo ng the underlying cause persisted. Design-Case-control study of 16 pri mary household cases and 32 controls of similar age and dietary habit. Packets of the implicated foodstuff manufactured on a range of days w ere examined for salmonella. All isolates of the epidemic phage type w ere further characterised by pulsed field gel electrophoresis. Results -27 cases were identified, of which 26 were in children. The case-cont rol study showed a strong association between infection with S agona p hage type 15 and consumption of a peanut flavoured ready to eat kosher savoury snack imported from Israel. S agona phage type 15 was isolate d from samples of this snack. The combined food sampling results from the United Kingdom, Canada, the United States, and Israel showed that contaminated snacks were manufactured on at least seven separate dates during a four month period between October 1994 and February 1995. Vo luntary recalls of the product successfully interrupted transmission. Conclusions-Rapid international exchanges of information led to the id entification of the source of a major outbreak of S agona in Israel an d of associated cases in North America. The outbreak showed the value of the Salm-Net surveillance system and its links outside Europe, both for increasing case ascertainment and for improving the information o n the duration of the fault at the manufacturing plant.