German officials believe they have solved a seven-year Listeria outbreak that included the death of one man.
Using next generation sequencing (NGS) methods, the Bavarian State Office for Health and Food Safety (LGL) helped identify a likely connection between Listeria infections in Lower Bavaria and in the district of Altötting since 2015 and a food company.
The company was not named by authorities but they described it as a small businesses in the district of Passau that had various customers in the region. Local media reported it was a produce company that supplied canteens and care homes but not retailers.
Alongside the results from the NGS analysis, there are indications of an epidemiological connection to those sick based on the sales area.
Low level of illness over many years
In 13 cases of illness in Lower Bavaria and Altötting, including the death of an 85-year-old man in 2015, the same type of Listeria monocytogenes has been detected, which indicates there is a common source of infection.
Two cases were reported in 2015, one in 2016, two in 2017, one each in 2018, 2019 and 2020, four in 2021 and one in 2022.
Recently, this type of Listeria was detected at the suspected company’s operations. Past surveys of patients and investigations by authorities had not found the food category responsible for disease.
When the LGL informed the local authority about the results of the analysis, officials stopped operations at the company on June 24 and ordered products to be returned with further testing ongoing at the LGL and investigations by local authorities continuing.
In early 2020, a look at human isolates using NGS by the Robert Koch Institute (RKI) found that a couple of listeriosis cases per year in different districts in Lower Bavaria and Altötting from 2015 to 2019 were related. Until this point, they were thought to be isolated cases with no connection to each other.
In cases where only a few people are affected over many years, it can be hard to find a common source as questioning ill people is difficult because of factors like the long incubation period, age of the patient and the variety of foods mentioned.
Only when there is a suspicion of a connection through typing isolates from patients, can consumption habits be compared and suggestions of a possible food source be determined.
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