The ECDC has identified a link between an outbreak of nine Listeria cases in Denmark and nine more infections between 2014 and 2018 in four other countries.

The European Centre for Disease Prevention and Control (ECDC) said there is a microbiological link between the outbreak of Listeria monocytogenes strain type (ST) 1247 in Denmark linked to fish and additional cases in Estonia, Finland, France, and Sweden. The latest case was in Denmark in February 2019.

Two cases in Estonia are from July 2014 and February 2016. Finland’s two cases date from August 2016 and December of that year, the sole case in France was in August last year. Four infections in Sweden occurred in February and July 2015 as well as January and March 2016.

In Denmark, the first person fell sick in December 2016, five cases were reported in 2017, one in 2018 and two in 2019. Two people died but all patients had other illnesses that put them at high risk for serious infections. Patients are five males and four females aged 52 to 90 years old.

Statens Serum Institut has been investigating the outbreak in Denmark since 2017. Earlier this month, it identified the source of infection as imported cold-smoked trout and salmon products from Estonia.

The Estonian fish processor, a company called M. V. Wool, rejected the link and said products are delivered to customers in accordance with limits set in EU Regulation 2073/2005 and are safe to eat.

Conformity of the products are checked by tests in accredited laboratories at the prescribed frequency, said the company in a statement on its Facebook page.

The regulation sets a limit of 100 colony forming units per gram of Listeria monocytogenes for products such as fish placed on the market during shelf-life.

The Danish importer, Food With You, issued a recall of smoked trout sold at Bilka and Føtex stores across the country after Listeria was found. Dagrofa also recalled smoked trout due to Listeria sold at MENY stores throughout Denmark.

Whole Genome Sequencing (WGS) analysis at the national level and by ECDC found all isolates from the 18 cases fall within two allelic differences meaning cases are likely linked by a common source of infection.

Listeriosis is a relatively rare but potentially severe foodborne disease that has been increasing in Europe since 2008. In 2016, 2,536 cases were reported, including 247 deaths.