Norovirus spread through fresh vegetables caused a gastric epidemic in Pirkanmaa
The number of infected people was approximately 300 in Tampere and 120 in Valkeakoski, with other infected cases in municipalities close to Tampere. Most of the cases were people who had eaten in cafeterias. The nature of the epidemic was studied by means of a survey of customers of nine cafeterias in Tampere and one in Valkeakoski.
About half of the people eating lunch in the cafeterias had suffered from a gastric disorder. The most common symptoms had been vomiting, diarrhoea, stomach ache and nausea. Some also had had a temperature or headache. In most cases, the symptoms had started between 26 and 27 July and ended in three days. About one fifth of those infected had had to seek medical assistance. Norovirus was isolated in samples from the patients. Further examination showed that the noroviruses from different municipalities were of the same genotype, which strengthened the evidence of a common source.
According to the survey, eating the fresh salad vegetables available in the cafeterias had increased the risk of becoming ill. The cafeterias used the same supplier of fresh vegetables. Norovirus could not, however, be identified in samples taken from the vegetables in cafeterias or the vegetable supplier. The inspection carried out at the premises of the vegetable supplier showed no defects in the handling of vegetables. The product from which the epidemic originated could not be ascertained on the basis of the survey or from vegetable samples. Both domestic and foreign vegetables had been delivered to the cafeterias. It is possible that one batch infected with the virus had spread the virus to other products handled on the same day.
The epidemic was the largest food-communicable norovirus epidemic in Finland. In previous years, norovirus spread in tap water has caused several larger epidemics with up to several thousand people infected. The norovirus infection is easily communicable and thus a small amount of pathogen in food products is sufficient to cause infection. In addition, the virus is easily communicable amongst humans or through contacting surfaces. Careful handling of food products and good hand hygiene are the best ways to prevent norovirus infection.
National Public Health Institute:
Tel. +358 (0)9 4744 8557
Finnish Food Safety Authority Evira:
Tel. +358 (0)20 77 24318
City of Tampere, Environmental Protection Department:
Tel. +358 (0)20 71 66393
Town of Valkeakoski, Department of Environmental Protection:
Tel. +358 (0)3 576 6669