Epidemiological update: multi-country outbreak of Listeria monocytogenes serogroup IVb, multi-locus sequence type 6 infections
Since the publication of the joint ECDC-EFSA rapid outbreak assessment on a multi-country outbreak of Listeria monocytogenes serogroup IVb, multi-locus sequence type 6 (ST 6) on 22 March 2018, three EU Member States have reported nine new confirmed outbreak cases.
As of 11 April 2018, this outbreak has been associated with 41 cases identified between December 2015 and March 2018. New confirmed cases were reported in Finland (5), Sweden (1) and the United Kingdom (3). The European outbreak case definition is available in the last published rapid outbreak assessment. The outbreak has intensified in the past two months, with six new confirmed cases reported in February and five in March (Figure 1).
Figure 1. Listeria monocytogenes PCR serogroup IVb, ST 6; confirmed outbreak cases by month of symptom onset*, European Union, 2015–2018 (n=41)
The outbreak was detected through whole-genome sequencing. Core genome multi-locus sequencing typing (cgMLST) analysis showed that all human isolates are within 5 allelic differences from the Finnish representative outbreak strain.
ECDC and the European Food Safety Authority (EFSA) published a joint outbreak assessment of this event on 22 March 2018 providing information on the human and food information. The assessment and the conclusions of the rapid outbreak assessment remain valid.