Series of Norovirus Outbreaks Caused by Consumption of Green Coral Lettuce, Denmark, April 2016

The objective of this investigation was to establish a possible food source of the outbreak. For the cohort studies, a case was defined as a person attending the common event and developing vomiting and/or diarrhea within three days. Upstream tracing of lettuce from all outbreak settings was conducted by way of collecting and comparing purchase and delivery information in the period of one week prior to the outbreaks. Tracing was performed through the distribution chain to the packer in Denmark and from there to the wholesaler in France. This was then followed by forward tracing of the incriminated batches of lettuce, revealing the full distribution chain. Two EU communication networks were used, the Rapid Alert System for Food and Feed (RASFF) and the European Center for Disease Prevention and Control (ECDC) communication platform for potentially cross-border foodborne outbreaks (EPIS-FWD).6 Culturing was performed for pathogenic bacteria, including diarrhoeagenic E. coli, Campylobacter, Salmonella and Yersinia.7 The presence of gastrointestinal viruses was assessed according to previous publications using a multiplex real-time PCR for rotavirus,8 sapovirus,9 human astrovirus and adenovirus (40+41).10 Norovirus analysis was performed using genogroup (G) specific primers11 by real-time RT-PCR. Sequencing of polymerase and/or capsid fragments obtained by RT-PCR using standard typing primers for the specific G, in this case GI11,12,13,14 was performed on an ABI 3500 (Thermo...
Source: PLOS Currents Outbreaks - Category: Epidemiology Authors: Source Type: research