Almost 200 people have been sickened in a multi-country Salmonella outbreak that has been ongoing for more than a year.

Overall, 196 Salmonella Mbandaka infections have been reported with 89 people sick in Finland and 81 in the United Kingdom. Patients also live in the Czech Republic, Estonia, France, Germany, Ireland, the Netherlands, and Israel.

Nineteen people were hospitalized, five had septicemia, which is caused by bacteria entering the bloodstream, and one person in the UK died. Cases have occurred across all age groups.

In September, the Finnish Institute for Health and Welfare (THL) reported 54 people were sick and 36 of 38 patients interviewed had eaten various chicken products before falling ill.

Chicken products suspected

Based on patient interviews from Finland and the UK, ready-to-eat (RTE) chicken products or fresh chicken used in sandwiches and wraps are the likely sources of infection. 

Finnish officials linked the suspected RTE products to an Estonian company, however, this could not be confirmed by trace-back work or microbiological evidence. The Estonian firm received processed chicken meat from different suppliers, including a Dutch company.

Epidemiological data and microbiological evidence from whole genome sequencing of human isolates indicate there are several sources through different distribution chains, with a likely common source further up the supply chain. New cases are likely to occur until the source has been identified and controlled, said the European Centre for Disease Prevention and Control (ECDC).

In May 2022, the UK reported a cluster of 31 Salmonella Mbandaka cases with 25 from England and three each in Scotland and Wales with sample dates between Sept. 2021 and April 2022. Four were admitted to the hospital and one person died.

In June, Finland reported nine Salmonella Mbandaka cases from different regions between April and May. Subsequent analysis confirmed the cluster was genetically close to the UK outbreak strains. In Finland, 10 of 73 interviewed patients were hospitalized and five had septicemia. The latest case was reported in Estonia on Oct. 17.

The Salmonella Mbandaka strain is different from the one detected in the multi-country outbreak linked to sesame-based products from Syria.

Patient interviews and sampling

In the UK, 18 of 26 cases reported eating RTE chicken products in the week before the onset of symptoms. Chicken slices and pieces used in sandwiches and wraps were frequently mentioned. Ten people purchased chicken from cafés and restaurants, including wraps, sandwiches, baguettes, and kebabs. Chicken products may have been distributed through retail as well as the catering sector. In most cases ate chicken bought fresh, including chicken breast, thighs, and the whole bird.

In Finland, 64 of 67 interviewed cases had eaten various chicken products before becoming ill. Fifteen people had consumed or purchased certain RTE products of three brands, which are sold in two of the largest grocery chains in Finland. One possible case, an asymptomatic staff member of a food company, who tested positive for Salmonella Mbandaka in September, was identified. This person had regularly consumed RTE wraps, like those reported in the 15 cases. Several had eaten out in restaurants.

In September, Estonian authorities took 15 environmental samples, including eight from non-food contact surfaces, at the company linked to the incident. Samples were also collected from RTE food products and processed chicken meat but all were negative. More tests were conducted in October but these did not detect Salmonella.

A total of 129 internal checks for Salmonella in 2022 by the company were also negative. The business does not sell products in the UK, which has reported the second-highest number of infections.

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