Fourteen countries have been affected since May 2016; Croatia, Denmark, Finland, France, Greece, Italy, Luxembourg, Slovenia, Belgium, Hungary, the Netherlands, Norway, Sweden and the UK.
Croatia reported the death of a five year old child and Hungary also recorded a fatal case.
Eleven confirmed cases travelled to Poland during the incubation period so it is likely to have also been affected.
Contaminated product still on market?
The outbreak peaked in the last week of September 2016 when around 60 cases were reported, according to the European Centre for Disease Prevention and Control (ECDC) and European Food Safety Authority (EFSA).
Control measures were then implemented at the farm and distribution level.
There was a maximum of two new cases reported each week in January and February this year.
The last case (as of 24 February) was from Norway, with a sampling date of 2 February indicating contaminated items were circulating until recently.
Dutch authorities said the outbreak, which had been ongoing since 2015, appeared to be over earlier this year.
Evidence from epidemiological, microbiological, environmental and tracing investigations identified eggs from three Polish packing centres as the vehicle of infection.
According to Polish authorities no S. Enteritidis-positive breeding flock was detected in 2016.
Investigations identified 18 S. Enteritidis-positive laying hen farms. Most of these, as well as the three packing centres, belong to the same Polish consortium and are considered to be interlinked.
It is also possible S. Enteritidis might have been introduced at a higher level in the food chain.
Country specific investigations
Dutch cases came from infected eggs from Polish companies with laying hens – named as Fermy Drobiu Woźniak (Wozniak Poultry Farms), Specjalistyczne Gospodarstwo Rolne, Ferma Drobiu Maciej Kubiaczyk and Ovotek Sp. z o.o, by the NCAE (Nederlandse Controle Autoriteit Eieren).
Fermy Drobiu Woźniak told us in November testing by an accredited laboratory on some samples did not show Salmonella in eggs, the firm has not responded to our recent requests for comment.
De Nederlandse Voedsel- en Warenautoriteit (NVWA) and NCAE sampled 5,000 eggs from suspected Polish companies and found S. Enteritidis on the outside.
The Rijksinstituut voor Volksgezondheid en Milieu (RIVM) determined it was the same bacteria as that which caused the outbreak.
EU/EEA countries reported 218 confirmed cases belonging to two distinct WGS clusters and 252 probable cases sharing the S. Enteritidis MLVA profiles 2-9-7-3-2 or 2-9-6-3-2.
These profiles differ from another S. Enteritidis outbreak which has 329 confirmed cases from four EU countries since 2014 but the source remains unknown.
The first isolates belonging to one of the WGS clusters associated with the Polish egg outbreak were identified in 2012 in the UK.
For 90 confirmed and probable cases where information was available, 26 were hospitalised.
Information is available for 127 confirmed or probable cases from five countries (Belgium, the Netherlands, Sweden, Slovenia and UK), with 98 (77%) reporting exposure to eggs or products containing eggs.
A case-control study in the Netherlands found cases were more likely than controls to have eaten out, but no exposure to specific items could be established with strong evidence.
Case interviews in Belgium and France linked sporadic cases and clusters of cases to two butchers in Belgium and interviews in Denmark linked four cases to the same restaurant.
Hungary investigated four outbreaks later found to be associated with the S. Enteritidis MLVA profile.
The first in August 2016 in Nógrád County had 44 associated cases; the second in September was in Budapest (57 associated cases); the third was in Békés County (41 associated cases), also in September and the last was in December in Csongrád County, with 12 associated cases.