Netherlands reports Salmonella cases as part of wider outbreak
Salmonella cases reported by the Netherlands have re-kindled investigations into an outbreak strain reported by four countries earlier this year.
Six EU countries have reported 147 Salmonella Enteritidis cases since July last year. Between February 2012 and April 2016, 101 historical isolates with outbreak strain characteristics (based on WGS or MLVA) were reported.
Netherlands launched an Urgent Inquiry in EPIS-FWD last month reporting an increase of S. Enteritidis phage type 8 with Multiple-Locus Variable number tandem repeat Analysis (MLVA)-pattern 2-9-7-3-2.
The Epidemic Intelligence Information System (EPIS) FWD (Food- and Waterborne Diseases and Zoonoses) is a web-based communication platform restricted to nominated public health experts.
The European Centre for Disease Prevention and Control (ECDC) said although the outbreak had been considered over in the first months of 2016, the new cases since May with identical MLVA type or falling in one of the two previously described WGS clusters confirm the outbreak is ongoing and additional cases have to be expected.
Based on the available information, it is likely that all cases are part of an outbreak caused by a common source which has been active since at least July 2015, it added.
Egg and chicken suspected vehicle
Since the middle of May there have been 64 cases (33 men, 31 women, range 0-87 years), compared to 15 in 2015.
Three cases, living in the same area, have been linked to one restaurant, and the suspected vehicle of infection was egg and/or chicken.
Belgium, Denmark, Norway, Sweden and the UK reported human cases with the same MLVA profile.
From May, 16 confirmed cases have been reported, belonging to a specific genetic cluster defined by WGS and 132 probable cases characterised by the outbreak MLVA profile.
Of these, 24 have a travel history to Austria (1), Czech Republic (1), Germany (1), Greece (13), Poland (7) and France and the Netherlands (1). All cases reported by Norway are travel-associated (Greece and Poland).
Earlier case increase
In January, the UK (Scotland) launched an Urgent Inquiry reporting an increase in cases of S. Enteritidis PT8 with the same MLVA profile and three additional countries reported cases but a common source or vehicle was not identified.
Whole Genome Sequencing (WGS) on a set of strains identified two different subtypes during the outbreak period in the UK and the Netherlands.
Cases belonging to the genetic clusters were identified since February 2012 however a large increase has been recorded since July 2015.
Derek Brown et al described a multi-country outbreak of S. Enteritidis which had sickened more than 80 people, earlier this year.
WGS identified two related but distinct clusters and confirmed 52 cases from England and Wales and 17 from the Netherlands, Finland and Denmark.
Brown et al suggested the outbreak could be associated with infection from a single source with two distinct strains or two or more vehicles from two different sources distributed through the same supply network.
The UK said S. Enteritidis has re-emerged in Scotland since early July with 29 cases as of 17 August. Cases' age range from less than one to over 80 and two were associated with travel to Greece and one to Poland.
Eight have been linked to three restaurants but no epidemiological links have been identified for other cases.
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