Epidemiological update: Multi-country outbreak of Salmonella Enteritidis infections linked to Polish eggs

epidemiological update

Since the joint ECDC-EFSA rapid outbreak assessment ’Multi-country outbreak of Salmonella Enteritidis infections linked to Polish eggs’ published on 12 December 2017, 15 EU/EEA countries (Belgium, Czech Republic, Denmark, France, Hungary, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Poland, Slovenia, Sweden and United Kingdom) have reported 336 confirmed, 94 probable and 3 new historical-confirmed cases associated with this ongoing multi-country outbreak of Salmonella Enteritidis in the EU/EEA. In the same period, seven historical probable cases were reclassified as excluded.

Overall, 1 412 cases have been found associated with this outbreak: 532 confirmed and 166 probable cases since 1 February 2017 and 343 historical-confirmed and 367 historical-probable cases between 2012 and 31 January 2017. In addition, no dates have been reported for four outbreak-confirmed cases, so they are unclassifiable as current or historical cases (Table 1).

Table 1. Distribution of cases by case classification and country, EU/EEA, February 2012 to November 2018 (n=1 420; 4 cases missing date of onset or sampling or receipt at reference laboratory), as of 12 November 2018

Reporting country

Confirmed cases

Probable cases

Historical-confirmed cases

Probable-confirmed cases

Total number of cases

Belgium

0

46

14

127

187

Croatia

0

0

4

0

4

Czech Republic

0

6

0

3

9

Denmark

16

0

6

2

24

Finland

0

0

0

1

1

France

21

0

8

0

29

Greece

0

0

0

2

2

Hungary

0

29

0

5

34

Ireland

12

0

4

4

20

Ireland

1

0

0

0

1

Italy

0

12

1

19

32

Luxembourg

4

0

5

0

9

Netherlands

8

25

90

164

287

Norway

22

18

11

32

83

Poland

25

0

0

0

25

Slovenia

0

7

3

0

10

Sweden

11

20

12

2

45

United Kingdom

412

3

185

6

606

Total

532

166

343

367

1408

              698

                710

 

Most outbreak cases were reported during the summer months (Figure 1). Due to reporting delays, additional cases are expected to be reported with onset in recent months.

A total of 112 confirmed or historical-confirmed cases were reported with travel history in an EU country during the incubation period and therefore were likely infected there. Countries where infections likely took place were Poland (25 cases identified from 2016 to 2018), Bulgaria (22 cases from 2015 to 2018), Cyprus (14 cases in 2016 and 2018), Portugal (11 cases from 2015 to 2017) and Hungary (10 cases from 2016 to 2018). Additional travel-associated cases were also reported (<10 cases per country) with travel history to Austria, Belgium, Greece, Italy, the Netherlands, Romania, Slovenia and Spain.

Figure 1. Distribution of cases by month of onset* and case classification (n=1 412; 4 cases missing any date of report), EU/EEA, January 2012 to October 2018, as of 12 November 2018

Salmonella Enteritidis - Distribution of cases by month of onset* and case classification (n=1 412; 4 cases missing any date of report), EU/EEA, January 2012 to October 2018, as of 12 November 2018
*: month of sampling or month of receipt by the reference laboratory if month of onset is not available.

The 2016 and 2017 European outbreak investigations identified eggs originating from Poland as the vehicle of infection in this outbreak (ECDC/EFSA rapid outbreak assessments published in March and December 2017). Outbreak-confirmed cases belong to four different WGS clusters.

Assessment

As reported in the previous ECDC/EFSA rapid outbreak assessment, in 2016 and 2017, evidence from epidemiological, microbiological, environmental and tracing investigations identified eggs originating from Poland as the vehicle of infections in this multi-strain outbreak. Control measures were implemented following these investigations. However, new outbreak cases were notified in 2017 and in 2018 with similar magnitude and temporal patterns. Based on the analysis of the travel-associated cases, it is likely that more countries where molecular typing is not performed routinely for human S. Enteritidis isolates are affected by the outbreak, including Bulgaria, Cyprus and Portugal.

Actions

ECDC monitors the occurrence of human cases associated with this threat and offers sequencing services for countries reporting probable cases of human S. Enteritidis isolates with MLVA profile 2-9-7-3-2 or 2-9-6-3-2 or
2-9-10-3-2 or 2-10-6-3-2 or 2-10-8-3-2 or 2-11-8-3-2. EU/EEA countries should consider interviewing new outbreak-confirmed cases.

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