A rise in the number of people getting sick from Campylobacter has been reported in recent weeks in Sweden. Since the end of July up to this past week, the number of people infected with Campylobacter has been between 160 and 200 per week.

The spike in human cases was preceded by an increase of Campylobacter in broiler flocks, according to data from the National Veterinary Institute (SVA).

The increase has been seen throughout the country and in all age groups.

Beginning in July, more positives for Campylobacter in Swedish chickens raised for meat production were also recorded. Infection in humans and presence in broiler flocks is more common in the summer.

A comparison with previous years is complicated by the impact of the Coronavirus pandemic but the median number for 2008 to 2019 varies between 150 and 170 cases per week for the same time period which makes the numbers in recent weeks only slightly increased.

However, last summer, the number of cases was peaking at around 150 during two weeks when an outbreak was taking place. Also, the pandemic effect is likely not as pronounced now as it was last year.

Link to chicken meat again
Previous studies have shown that infections are often linked to raw chicken meat, which makes it likely that an increased presence of Campylobacter in chickens is the cause of the rise in human cases, according to Folkhälsomyndigheten (the Public Health Agency of Sweden).

In the next few weeks, Folkhälsomyndigheten will collect samples from patients for analysis and typing as part of the microbiological monitoring program to identify the presence of common sources of infection.

“In previous years, comparisons have been made of Campylobacter from fresh chicken bought in a store during the summer with Campylobacter from cases of human disease during the corresponding period. They have shown that about a third of the cases can be linked to fresh chicken meat. There is much to suggest that the increase in cases in humans and the incidence in broiler flocks also now have a direct connection,” said Rikard Dryselius, from Folkhälsomyndigheten.

In total, 3,434 Campylobacter cases were reported in 2020 – the lowest number since 1998.

However, a major outbreak occurred lasting until late autumn and contributing to a spike in the number of people infected in Sweden during the second half of the year. There was a rise in cases in August after an increased proportion of Campylobacter in broiler flocks was noted. The source of infection was mainly linked to a large chicken producer where poorly cleaned transport cages were cited as one cause.

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