Detection of human norovirus from frozen raspberries in a cluster of gastroenteritis outbreaks

• Published in: Euro surveillance : bulletin européen sur les maladies transmissibles Vol. 14; no. 49
• Main Authors: Maunula, L, Roivainen, M, Keränen, M, Mäkela, S, Söderberg, K, Summa, M, von Bonsdorff, C H, Lappalainen, M, Korhonen, T, Kuusi, M, Niskanen, T
• Format: Journal Article
• Language: English
• Published: Sweden 10-12-2009
• Subjects: Caliciviridae Infections - epidemiology; Cluster Analysis; Disease Outbreaks - statistics & numerical data; Female; Finland - epidemiology; Food Contamination - statistics & numerical data; Freezing; Fruit - microbiology; Gastroenteritis - epidemiology; HIV Infections - epidemiology; Humans; Incidence; Male; Norovirus; Population Surveillance - methods; Risk Assessment; Risk Factors; Finland
• ISSN: 1560-7917; 1560-7917
• DOI: 10.2807/ese.14.49.19435-en

We describe a cluster of norovirus outbreaks affecting about 200 people in Southern Finland in September and October 2009. All outbreaks occurred after consumption of imported raspberries from the same batch intended for the catering sector. Human norovirus genotype GI.4 was found in frozen raspberries. The berries were served in toppings of cakes in separate catering settings or mixed in curd cheese as a snack for children in a daycare center. The relative risk for consumption of the berry dish was 3.0 (p <or= 0.05) at the daycare centre. Human norovirus GI.4 was also detected in samples from two patients, and in berries. Both shared identical partial capsid sequences. Based on the results of epidemiological, trace-back and laboratory investigations it was concluded that one particular batch of frozen raspberries was the source of all outbreaks.