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

L Maunula; M Roivainen; M Keränen; S Mäkelä; K Söderberg; M Summa; C H von Bonsdorff; M Lappalainen; T Korhonen; M Kuusi; T Niskanen

doi:10.2807/ese.14.49.19435-en

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Detection of human norovirus from frozen raspberries in a cluster of gastroenteritis outbreaks
L Maunula¹ , M Roivainen² , M Keränen³ , S Mäkelä⁴ , K Söderberg¹ , M Summa¹ , C H von Bonsdorff¹ , M Lappalainen⁵ , T Korhonen² , M Kuusi² , T Niskanen⁶
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Affiliations: ¹ Department of Food and Environmental Hygiene, University of Helsinki, Finland ² Institute of Health and Welfare, Helsinki. Finland ³ Regional Food Inspection Authority, Lahti, Finland ⁴ Regional Food Inspection Authority, Social and Health Care Group, Päijät-Häme, Finland ⁵ Laboratory Division (HUSLAB), Department of Virology, Helsinki University Central Hospital, Helsinki, Finland ⁶ Finnish Food Safety Authority Evira, Helsinki, Finland

Correspondence:
L Maunula
leena.maunula helsinki.fi
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Citation style for this article: Maunula L, Roivainen M, Keränen M, Mäkelä S, Söderberg K, Summa M, von Bonsdorff C H, Lappalainen M, Korhonen T, Kuusi M, Niskanen T. Detection of human norovirus from frozen raspberries in a cluster of gastroenteritis outbreaks. Euro Surveill. 2009;14(49):pii=19435. https://doi.org/10.2807/ese.14.49.19435-en Received: 24 Nov 2009

Abstract

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 ≤ 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.