An outbreak of calicivirus associated with consumption of frozen raspberries

In April 1988, an outbreak of gastroenteritis occurred among employees in a large company in Helsinki, Finland. A retrospective cohort study, using a self-administered questionnaire, was carried out to ascertain the cause and extent of the outbreak. To meet the case definition, employees had to have had diarrhoea and/or vomiting since 2 April, 1998. A subanalysis was made in the biggest office, consisting of 360 employees, of whom 204 (57 %) comp leted the questionnaire. Of these 108 (53 %) met the case definition. Emplo yees who had eaten raspberry dressing were more likely to meet the case def inition than those who had not (Attack Rate (AR) 65 % versus AR 18 % Relati ve Risk, (RR) 3.7, 95%, Confidence Intervals (CI) 2.0-6.7). Four stool spec imens obtained from affected kitchen staff who had all eaten the raspberry dressing and who had all become ill simultaneously with the employees were positive by polymerase chain reaction (PCR) for calicivirus. The data sugge st that the primary source of the outbreak was imported frozen raspberries contaminated by calicivirus.