Epidemiology and Infection

Table of Contents - February 2012 - Volume 140, Issue 02  

Rota- and noroviruses

Multiple norovirus outbreaks linked to imported frozen raspberries

E. SARVIKIVIa1a2 c1, M. ROIVAINENa1, L. MAUNULAa3, T. NISKANENa4, T. KORHONENa1, M. LAPPALAINENa5 and M. KUUSIa1

a1 National Institute for Health and Welfare (THL), Helsinki, Finland

a2 European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden

a3 Department of Food Hygiene and Environmental Health, University of Helsinki, Finland

a4 Finnish Food Safety Authority Evira, Helsinki, Finland

a5 Helsinki University Hospital, Laboratory Services (HUSLAB), Helsinki, Finland

SUMMARY

In 2009, the number of foodborne norovirus outbreaks in Finland seemed markedly high, and many outbreaks seemed to be linked to imported frozen raspberries. We reviewed the data regarding all notified foodborne outbreaks in 2009 in Finland in order to assess the magnitude of the problem and to summarize the information on raspberry–linked outbreaks. Between March and August, 13 norovirus outbreaks affecting about 900 people could be linked to imported frozen raspberries. Two raspberry samples corresponding to two batches of raspberries were positive for norovirus. These two batches proved to have been the likely source in six of the 13 outbreaks. Analytical studies had not been conducted for six outbreaks, and virological test results were inconclusive in two. However, combining epidemiological and microbiological methods often enabled finding the source, as exemplified in investigation of a large school outbreak. To ensure prompt control measures in similar situations in the future, both aspects of outbreak investigations should be strengthened.

(Accepted February 16 2011)

(Online publication March 22 2011)

Key Words:

Correspondence:

c1 Author for correspondence: Dr E. Sarvikivi, Department of Infectious Disease Surveillance and Control, National Institute of Health and Welfare (THL), PO Box 30, 00271 Helsinki, Finland. (Email: emmi.sarvikivi@thl.fi)

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