German public health authorities have reported an outbreak of Listeria monocytogenes serotype 1/2a in the south of the country that has been on-going since 2012. The source of the outbreak has not yet been identified.
A total of 66 cases have been recorded since November 2012, but the number of cases has risen each year and 28 have been confirmed in 2015. Four cases occurred in pregnant women and there have been six reported deaths related to the outbreak.
The outbreak strain of L. monocytogenes has a previously unseen pulsed-field gel electrophoresis (PFGE) pattern and the outbreak has been confirmed using next generation sequencing techniques. No cases caused by this strain have been reported outside Germany.
Investigators have not yet established the source of the outbreak, but it seems likely to be food related. There are no obvious links to a specific institution and fish and cheese products have also been largely ruled out. A PCR-based protocol for detection of the outbreak strain has been developed to quickly screen isolates from food samples.
A report on the investigation has been published in the journal Eurosurveillance and can be found here.