In 2018, 156 cases of listeriosis were reported in England and Wales and 32 people died, a higher figure than in the previous year (135). The source of infection was not found for three of four Listeria outbreaks in England in 2018, with the one solved being an international outbreak that involved 12 cases in England from 2015 to 2018 and was traced to frozen sweetcorn and vegetables produced by Greenyard in Hungary.
The company found the cause of contamination, a persistent presence of Listeria monocytogenes in one of the freezing tunnels, and closed down this tunnel at the plant. In June 2019, the factory was sold to Roger & Roger, a producer of potato and corn snacks. This multi-country incident included 54 clinical cases of listeriosis in Australia, Finland, Sweden, Denmark, Austria, and the UK with 10 deaths. The outbreak was detected in Finland using whole-genome sequencing (WGS).
Traceability information indicated that frozen corn was produced in Hungary and packed in Poland. It was found that people had eaten the frozen sweetcorn uncooked, although instructions on the packaging told consumers to cook it. Implicated frozen products were distributed to 116 countries.
Most infections were in those older than 80, particularly in men aged 70 and over. Of the 18 cases in the 10 to 19 and 20 to 29 age groups, 17 were female and 14 were associated with pregnancy.
In England, the North East had the highest incidence rate whilst the East of England had the lowest. Wales reported five cases in 2018. July was the peak month for listeriosis reporting in 2018. Cases were infected with different strains of Listeria monocytogenes and no outbreaks influenced this peak. In 2016 and 2017 numbers peaked in October and July respectively.