SSI: Modest Campylobacter increase but Salmonella stable

By Joseph James Whitworth

- Last updated on GMT

Picture: Getty/Dr_Microbe
Picture: Getty/Dr_Microbe
Four times as many people become sick from Campylobacter compared to Salmonella in Denmark, according to the Statens Serum Institut (SSI).

Recent years have seen a modest increase in Campylobacter cases whereas the number of Salmonella infections has remained stable in the past five years.

Campylobacter infection remains the most frequent cause of gastrointestinal infections in Denmark.

For people with no travel history, eating chicken meat is an important source of infection but minced beef and fresh strawberries are also risk factors.

Campylobacter up in 2016 but down in 2017


A Campylobacter outbreak of more than 5,000 cases​ from August 2016 to June 2017 was caused by a large chicken producer delivering contaminated meat to stores. The reason was reported to be incorrect equipment installation meaning dirty water was accidentally used to wash transport cages. 

At the beginning of 2017 an outbreak was investigated where 15 people from five counties were diagnosed with EHEC O145: H28 (stx2a). Source of infection could not be identified but as cases fell ill over a long period it was suspected a long-life food was the vehicle of infection.

Seventeen conference participants fell ill in early 2017 and five were verified as Yersinia enterocolitica type 3. Poorly fried pork was suspected to be the source but no food was left for sampling

In 2016, 4,678 cases of Campylobacter spp infections were recorded which was 7% more than the previous year and the highest ever recorded. A decrease was seen in 2017 as 4,243 cases were noted.

Species was determined for a subset (435) of the strains and 27 were C. coli, whereas the remaining were C. jejuni.

SSI said introduction of PCR diagnostics might impact the number of positive cases recorded.

In the National Food Outbreak Database, 2016 and 2017 saw three and two outbreaks of Campylobacter, respectively.

In June 2016, an outbreak in the Copenhagen area occurred among employees of several companies who used the same catering firm as a lunch provider.  

A total of 103 people from 19 companies were affected and the investigation indicated the source was cross contamination in handling of duck meat and fresh greens.

In June 2017, 66 of 245 schoolchildren fell ill after visiting a farm near Aarhus where they had raw milk from the barn.

The share of people infected abroad exceeded what has previously been recorded. It was 38% in 2016 and 47% of the patients in 2017.

Disease burden was equally distributed across all age groups but with excess representation of those in their twenties.

Salmonella statistics


In 2017, 162 outbreaks were reported with 2,320 cases. The number of sick ranged from two to 230 per outbreak. In 36 outbreaks there was a suspected link to food​. The most common cause of foodborne outbreaks was norovirus (seven), followed by enterohemorrhagic E. coli (EHEC) and Campylobacter (three each).

The number of zoonotic Salmonella cases was 1,074 in 2016 and 1,067 in 2017.

As in previous years, those below five years old accounted for a relatively high number of diagnosed infections partly reflecting that more people in this age group undergo such testing.

S. Enteritidis was the most frequent serotype in both years.

As was the case in previous years, the monophasic variant of S. Typhimurium, including isolates with the formula “1,4,[5],12:i:-” was seen more frequently than S. Typhimurium itself in 2016 and 2017.

S. Enteritidis, S. Typhimurium and the monophasic variant accounted for about half of infections.

A total of 109 different serotypes were registered in 2016 and 103 in 2017. Many of these were acquired during foreign travel.

In 2017, the SSI transitioned to routine whole genome sequencing of all isolates.

Salmonella outbreaks are mostly caused by S​. Typhimurium or the monophasic variant.

In 2016-17, 14 outbreaks were recorded with these types. The source of infection was found in six of 14 outbreaks and all were related to pork. The largest comprised 21 patients from December 2016 to April 2017.

Another large S​. Typhimurium outbreak affected 13 patients, mainly children, in 2017.

Results from a case-control study revealed a high probability that it was caused by so-called Fuet Coins snack sausages produced in Spain and sold in supermarket chain Netto.

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