Public health officials in Norway are investigating an outbreak of Salmonella with up to 20 patients.

Folkehelseinstituttet (the Norwegian Institute of Public Health) reported the outbreak of Salmonella Enteritidis has seen 10 people need hospital treatment.

A dozen people have been diagnosed with the outbreak strain and there are eight suspected cases. Samples were taken from the end of January through the end of February.

Trying to find the source
Patients are geographically spread across Norway. Nine live in Viken, three in Oslo, two in Innlandet, while Vestfold og Telemark, Agder, Rogaland, Vestland, Møre og Romsdal and Nordland all have one patient. Those sick are aged from 11 to 91 years old and 60 percent are women.

Folkehelseinstituttet suspects the source of infection is a widely distributed food but the exact vehicle is not yet known.

Outbreak investigations have been started with the relevant local units, the Veterinary Institute and Mattilsynet (the Norwegian Food Safety Authority).

Patients are being interviewed and Mattilsynet is taking samples from food products in the homes of those who are infected.

Hilde Marie Lund, from Folkehelseinstituttet, said it was too early to say if it was a limited outbreak or there will be an increase in people affected.

She added the large proportion of patients admitted to hospital may be related to the overall relatively high age of those affected but this is being investigated further.

No link to EU outbreak; results pending on Swedish outbreak
The outbreak strain has the same sequence type (ST) as the one causing Salmonella Enteritidis infections linked to poultry products from Poland that has affected nine countries, which is ST-11, however the Norwegian outbreak strain does not cluster with strains within this outbreak, meaning they are not related. Norway also has no patients in the outbreak traced to frozen breaded poultry items.

Every year, between 900 and 1,300 cases of salmonellosis are reported to Folkehelseinstituttet with most people infected abroad.

Experts are in the process of comparing the outbreak sequence with one reported from Sweden to see if they are linked.

The Swedish Salmonella Enteritidis outbreak has affected a dozen people. Eight of those sick are children younger than 10. The first patient was reported in December 2020. The others became ill after late January. Investigations are ongoing to identify the source of infections.