The number of foodborne outbreaks was down but the amount of people falling sick was up in Denmark in 2019 compared to the year before.

This past year, 51 outbreaks were reported with 1,929 patients. Eighteen of the outbreaks were national events, of which four were part of international incidents. The most frequent setting was restaurants with 15 outbreaks affecting 534 people.

In 2018, 1,600 people were affected by 64 outbreaks. Norovirus remained the most frequent cause of foodborne outbreaks.

Large outbreaks
In 2019, Clostridium perfringens was associated with 10 outbreaks affecting 551 people compared to five in 2018 affecting 107 people. Incidents involving Clostridium perfringens are usually caused by insufficient cooling of large portions of food, like meat sauces and sous vide or slow roasted meats.

The largest outbreak, involving 268 people, was caused by insufficient cooling of minced meat sauce packed with other items into chilled ready-to-heat meals and delivered to 3,500 subscribers of a meal box delivery scheme. Another outbreak of 101 people was due to a buffet meal. Sandwiches were blamed for 17 illnesses.

Norovirus saw a rise in outbreaks in 2019 compared to 2017. This past year there were 19 outbreaks with 932 people affected.

One outbreak was caused by oysters harvested in Denmark by a person in a closed zone. They were served raw at a private party. Two others affecting 64 people were linked to oysters imported from other EU countries. Two large outbreaks with 205 and 180 cases were linked to composite meals. Open sandwiches sickened 84 people in one outbreak while cakes from a retail bakery affected 14 people.

For the third year in a row, the number of Campylobacter infections increased. However in 2019 the rise was larger than previously seen, with 5,389 cases compared to 4,546 in 2018. Nine foodborne outbreaks were investigated and six had Danish produced chicken meat as the source.

Steady Salmonella
Infections with Salmonella remain comparable to previous years with 1,120 cases in 2019, and 1,168 and 1,067 in 2018 and 2017, respectively. Salmonella Enteritidis and Salmonella Typhimurium including the monophasic variant (4,[5],12:i:-) continue to be the most common serotypes with 310 and 272 cases.

Nine national Salmonella outbreaks were recorded. Three were caused by monophasic Salmonella typhimurium 4,[5],12:i:- and Danish produced pork meat was the source in two of them.

The third was the largest with 57 patients. It was related to an international investigation involving Finland and Sweden with more than 200 registered cases from 2018 to 2019 with a WGS profile similar to that of the Danish outbreak. However, the suspected food vehicle for the international cluster was pork meat products and the suspected source in the Danish outbreak was locally produced minced beef meat.

An outbreak with Salmonella Coeln from May to August involved 26 cases aged eight to 87 years old but interviews did not reveal the source. An outbreak with Salmonella Derby was investigated from April to June and involved 11 cases, aged 45 to 79 years old. The national event was probably caused by pork meat products from a Danish slaughterhouse.

Of the other outbreaks, eight fell ill in a Salmonella Enteritidis outbreak, a Salmonella London outbreak sickened four, Salmonella Mikawasima affected three, and Salmonella Muenchen sickened four. The suspected source for the Salmonella Mikawasima incident was vegetables or lettuce.

Similar to previous years, the most important food source was Danish produced pork with 8 percent of cases, according to a source attribution model. It attributed 250 of 469 infections to a food source. Pork was followed by imported duck with 6.5 percent. It is the first time such a large proportion of cases has been attributed to this food. The third most common source was imported pork followed by Danish produced table eggs.

More than 40 percent of cases were related to travel. Similar to previous years, most travel-related patients went to Turkey, Thailand and Egypt.

Listeria and STEC
Sixty-two Listeria cases were recorded in 2019 compared to 47 the year before. An outbreak of Listeria monocytogenes ongoing since 2016 was solved. It included 11 cases, of which three were from 2019. Salads including hummus from a small retailer in Jutland seemed to be the common food source. Swab samples and samples of products from the shop found Listeria. These isolates clustered with those from patients in the outbreak.

Shiga toxin-producing E. coli (STEC) continued to rise and was behind 630 illnesses compared to 495 in 2018. The number of registered STEC cases has increased every year since 2015.

STEC O157 sickened the most with 60 people compared to 43 the year before. It was followed by O26 and O103 both with 32 infections, O146 with 31 and O63 with 26. A STEC O157 outbreak affected 13 people but the source was not found.