The number of outbreaks and people sick in them declined in Norway in 2023, but this past year saw the country record one of its most serious-ever E. coli outbreaks.

Twenty-five outbreaks were caused by contaminated foodstuffs, with 518 people sick. This is down from 34 outbreaks and 628 cases in 2022. For eight outbreaks with 290 patients, the agent was unknown.

The most common agent in foodborne outbreaks in 2023 was norovirus on five occasions. Three were due to Salmonella, and two each because of cryptosporidium and enterohaemorrhagic E. coli (EHEC).

The norovirus outbreaks sickened 105 people. Salmonella Napoli, Salmonella Kintambo, and another serotype affected 14 people. The E. coli incidents sickened 36 people and 23 patients were affected in the cryptosporidium outbreaks.

One Campylobacter outbreak had 16 cases, and one Bacillus outbreak sickened 15 people. Ten cases were reported in an E. coli outbreak and seven in a Listeria outbreak. Two Clostridium botulinum cases were linked to eating Spanish omelet (tortilla de patata) in Spain.

Four outbreaks were traced to restaurants, cafes, pubs, and fast food outlets, and three each to hotels or other accommodation and company workplaces.

Vegetables and herb products were behind four outbreaks with 40 cases. Drinking water caused two outbreaks with 150 patients. Beef and cereal-based products were both linked to two outbreaks.

Outbreak examples
A national E. coli O26:H11 outbreak affected 24 people, nine children developing hemolytic uremic syndrome (HUS). Norwegian officials said it was one of the largest and most serious E. coli outbreaks the country had ever seen.

Cases were between 1 and 55 years old, with 15 males and nine females. HUS is a severe complication associated with E. coli infections that causes kidney failure and can lead to brain damage and other lifelong complications.

Nordfjord Kjøtt recalled fresh and frozen burgers sold at Rema 1000 stores. The outbreak strain was detected in frozen hamburgers from the business.

An E. coli O157 outbreak with 12 cases was found to be linked to burgers or ground (minced) meat, thanks to patient interviews. Ten people were hospitalized, but there were no HUS cases.

The Salmonella Kintambo outbreak with five cases was traced to sesame seed products from Syria. Three people ate such products before becoming ill. Product testing found Salmonella Kintambo and Salmonella Amsterdam in Halva from Syria. Whole genome sequencing data showed that Salmonella Kintambo from patients and a sesame seed product were similar.

Norway has had 13 cases in this multi-country outbreak linked to contaminated tahini and halva since 2020. People have been infected by Salmonella Havana, Salmonella Mbandaka, Salmonella Orion, Salmonella Kintambo, Salmonella Senftenberg, and Salmonella Amsterdam.

In mid-June 2023, one case of Listeria monocytogenes was reported with the same genotype as a previous outbreak of listeriosis in 2022 linked to smoked salmon. Between June and July, seven cases were found. Six people said they had eaten smoked salmon or smoked trout from one producer before becoming ill.

The outbreak strain was found in two unopened packs of smoked salmon from Troll Salmon, which one patient had at home. It was later also found in product samples taken from the producer. The firm temporarily closed to clean and replac some equipment.

imported leafy vegetables were suspected to be behind a Salmonella Napoli outbreak with seven patients. Four sick people were hospitalized.