Detected Salmonella outbreaks double in Denmark

There were double the amount of Salmonella outbreaks detected in Denmark last year compared to 2016, according to the 2017 annual report on zoonoses.

A total of 63 foodborne disease outbreaks with 1,151 patients were recorded last year compared to 49, in 2016. The largest, involving 86 people, was a local outbreak caused by Clostridium perfringens.

This figure includes 25 Salmonella outbreaks, which is twice as many as the year before and up from three in 2015. Danish officials said the increase is primarily because of new methods to detect more outbreaks.

The National Food Institute, Technical University of Denmark, prepared the report with Statens Serum Institut – the national institute of public health – and the Danish Veterinary and Food Administration (Fødevarestyrelsen).

”Statens Serum Institut has used whole genome sequencing since 2017 to type bacteria from all Salmonella patients in Denmark. This is a more accurate method of identifying the bacteria’s DNA and as such the correlation between patients. When we are able to cluster patients, we can also work in a more targeted way to identify the foods that are making people sick,” said Luise Müller, an epidemiologist from Statens Serum Institut (SSI).

A total of 1,067 Salmonella infections were reported among Danes in 2017. This figure has remained stable over the past seven years. It was 1,074 in 2016. The two most common strains were Salmonella Typhimurium, including monophasic strains, and Salmonella Enteritidis.

Approximately half of the Salmonella cases in 2017 were associated with travel abroad. People most often became infected in Thailand or Turkey.

Danish pork caused the most infections among people infected with Salmonella in the country. It was the source in 8.2 percent of the infections, followed by imported pork and chicken meat at 6.9 percent and 3.5 percent respectively. In 2017, no infections were caused by Danish chicken meat.

“We are pleased that once again we see no registered cases of illness related to Danish chicken meat. In fact, Salmonella has not been detected in Danish chicken meat in five out of the last seven years,” said senior scientific officer, Birgitte Helwigh, from the National Food Institute.

Campylobacter continued to be the cause of the most foodborne infections in Denmark in 2017 with 4,257 cases of illness but this was down from 4,677 in 2016. Two outbreaks were recorded in 2017, which made 72 people ill. Both were related to consumption of unpasteurized milk.

In May this year, authorities launched a new action plan for 2018-2021 aimed at reducing Campylobacter infections. The goal is to cut the number of registered human infections by 5 percent a year until 2021. Results from a case-control study by SSI and a source attribution model developed by the Technical University of Denmark (DTU) found that cattle may be a source of Campylobacter infection.

Norovirus accounted for 10 outbreaks affecting 298 people. This is a large decrease compared to the 1,178 people affected by such outbreaks in 2016. Infection with Norovirus is not notifiable in Denmark.

In total, 58 cases of Listeria monocytogenes infection and 12 deaths were reported in 2017 compared to 39 cases in 2016.

Shiga toxin producing E. coli (STEC) cases rose from 269 in 2016 to 346 last year. The O157 serotype was responsible for 50 cases compared to 37 in 2016 and other O-groups or non-typeable strains for 215 infections versus 204 in 2016.

Yersinia enterocolitica infected 80 children, four confirmed, with a link to improper heating or possible cross contamination of pork meat served as part of a dinner.

Bacillus cereus infected 91 patients in four outbreaks. Outbreaks involving this agent are traditionally caused by insufficient cooling of large portions of food like various meat sauces. The source of one outbreak appeared to be various pieces of meat prepared by cooking at low temperatures (<100 degrees Celsius) for many hours followed by cooling and reheating prior to serving.

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