Isolates associated with the outbreak have been identified since 2014 with 329 confirmed cases.
Six countries have also reported 38 probable cases.
The strain caused an outbreak that was investigated from May to October 2015 in Spain and the UK.
France, Ireland, Spain and the UK reported illnesses last year related to the 2015 cases, suggesting they are part of a common source outbreak, said the European Centre for Disease Prevention and Control (ECDC).
Non-human isolates sampled from an omelette in 2015 and the shell and interior of eggs at two different case-related homes in Spain in 2016 provided a strong indication of a common source.
No positive findings have come from the farm where the eggs originated.
Traceback investigations in France and the UK are establishing origin of the hens’ eggs from catering premises associated with multiple cases.
Multiple egg suppliers in the UK have been identified that sent eggs to catering premises visited by cases but no producer or supplier has been linked to the outbreak.
The UK reported a cluster of 17 cases of S. Enteritidis through the Epidemic Intelligence Information System for Food- and Water-borne Diseases and Zoonoses (EPIS-FWD) in November last year.
It was detected in Scotland between early September and late October.
Seven cases were linked to an outbreak in a restaurant and three reported travel to Spain and Portugal.
Whole Genome Sequencing analysis by Public Health England (PHE) showed the strain belonged to the same WGS cluster as that of the outbreak in the UK and Spain in 2015.
Between May and October 2015, PHE investigated an outbreak of S. Enteritidis with 136 cases, 12 of which had travelled to Spain, and established a link to hen eggs.
The UK noted the re-emergence of the strain causing the 2015 and 2016 outbreaks through the Early Warning and Response System (EWRS).
WGS analysis on human isolates from France, Ireland and Spain and the UK revealed a multi-country cluster.
French and Spanish investigations
France noted eight confirmed cases between November 2015 and October 2016 including two foodborne outbreaks.
In an outbreak from late 2015 eight people developed symptoms of salmonellosis after sharing a ‘gratin’ made with fresh eggs.
Traceability was impossible as the producer had no register or bills and the establishment was closed.
The second outbreak in September 2016 saw 23 people develop symptoms of salmonellosis after eating ‘tiramisu’ made with fresh eggs in a restaurant.
Eggs in the restaurant and at the farm yielded negative results for Salmonella.
ANSES suspected the use of other eggs which were untraceable, environmental contamination or a healthy carriage by food handlers in the restaurant.
Ireland had two confirmed cases with onset in August 2016 and Spain had 34 confirmed cases from April 2015 to September 2016.
S. Enteritidis isolates were detected in the interior and shell of two samples from eggs from the fridge of one Spanish sporadic case and a family cluster of three cases between July and September 2016.
Spanish authorities traced eggs to a single large farm and inspected the barns and packaging premises but they were all negative for Salmonella.
Denmark reported four probable cases reported in August, September and November 2016 as did The Netherlands but in August, September and October.
Norway had two probable cases with sampling in August 2016, Slovenia one probable in October and Sweden four probable cases with onset in August–September and December.
Eight countries submitted MLVA data for S. Enteritidis to The European Surveillance System (TESSy).
Six of these have reported 130 S. Enteritidis isolates with the Multi Locus Variable-Number Tandem Repeat (MLVA) type 2-12-7-3-2 and six isolates with the MLVA type 2-14-7-3-2.
In 2014, a multi-country outbreak was associated with German eggs characterised by isolates with the MLVA profile (2-12-7-3-2).
However, there are more than 100 Single Nucleotide Polymorphisms (SNPs) difference between the current and past outbreak indicating no association between them.
The MLVA type is also different than the one which has caused 183 confirmed and 246 probable S. enteritidis cases in ten countries which has profiles 2-9-7-3-2 and 2-9-6-3-2.