Outbreak 1
On 23 June, a group of 15 people met at a private party, where they ate homemade cake containing cream and raspberries. One or two days after, 12 people fell ill with gastrointestinal symptoms. Stool samples from two patients were tested and found positive for norovirus by PCR.

Outbreak 2
On 2 August, there was a family gathering of 11 people on the west coast of Sweden. Cheesecake with raspberries was served at the party and was eaten by all of the guests. The following day, 10 people fell ill with signs and symptoms typical of norovirus infection. Later, two secondary cases were reported. No faecal samples were taken, as the patients had already recovered by the time the outbreak was notified to the authorities. During the outbreak investigation it was determined that the raspberries in the cheesecake were of the same brand as in the first outbreak and imported from China.

Outbreak 3
On 24 August a school class with about 30 pupils aged 13 prepared drinks with raspberries. A mother of one of the children reported that her child had become ill on 26 or 27 August. The county medical officer carried out a cohort study and it was discovered that 12 children had been ill. The incubation period was 24-36 hours, the symptoms vomiting, fever, diarrhoea and headache. The duration of disease was 1-3 days. Faecal samples from two children tested positive for norovirus by PCR. Leftovers of raspberries in a plastic bag were saved for later analysis. These raspberries were the same brand as the other outbreaks.

Outbreak 4
On 25 August, a meeting took place with nine participants. The guests ate baguettes with filling from a catering company and a homemade raspberry parfait for dessert. Following this meeting, all nine people fell ill. One stool sample was taken for testing, and this was positive for norovirus. Raspberries were left over and saved for testing – results are pending. These berries were also the same brand as in the previous outbreaks.

Conclusion
All of the suspected raspberries in these outbreaks were the same brand, and from the same distributor in Sweden who imported these from China. Raspberries were left over in two outbreaks and results of further tests on the raspberries are pending. On 23 August two batches of raspberries, were withdrawn from the market.

Outbreaks of gastroenteritis caused by norovirus from frozen imported raspberries have been reported from several European countries in recent years [1,2,3]. Since 2000 in Sweden, there have been 11 outbreaks of gastroenteritis caused by norovirus where the suspected food has contained raspberries (database at Smittkyddsinstitutet).