Sweden is once again battling a rise in the number of Campylobacter infections after a temporary decline. A common source related to chicken has been identified.

Since August, the number of people who have contracted campylobacteriosis has been unexpectedly high. The increase in disease was preceded by a greater proportion of broiler flocks with Campylobacter.

Officials warned that higher sickness rates in recent weeks indicates that problems remain.

To investigate the increase, comparisons of Campylobacter from broilers of major Swedish producers and from sick people have been carried out. Results show that parts of the rise, both during summer and earlier in the autumn, can be traced to a common source. The work was done by Folkhalsomyndigheten (Public Health Agency of Sweden) and the National Veterinary Institute (SVA).

Public health officials first reported an increase in the number of people falling ill from Campylobacter in August.

September decline temporary
There is a general rise in most of Sweden’s counties. Age and gender of patients looks similar when comparing cases before and after August 2020 and to infections from previous years. Slightly more men than women are sick and infections are most common in people aged between 40 and 70 years old.

Rikard Dryselius, a microbiologist at Folkhalsomyndigheten, said at the end of September there had been a decrease in the number of sick people.

“Data about the number of Campylobacter positive poultry flocks from Swedish National Veterinary Institute available at that time also indicated a decrease during the preceding weeks. Unfortunately, the decline turned out to be only temporary as the number of cases has risen again in October,” he told Food Safety News.

“As long as the numbers are high in the poultry flocks, we will continue to see higher levels of human cases, specifically when large poultry producers are affected.”

Due to the Coronavirus pandemic, the size of the rise is difficult to estimate but after 50 cases were reported from Sept. 21 to 27, numbers gradually increased to about 100 per week during mid- to late October.

Poultry connection
Folkhalsomyndigheten only gets sporadic information on what people ate before becoming ill with Campylobacter and there has not been an epidemiological study.

“Typing results with whole genome sequencing from August and September have identified several outbreak strains that are common between both poultry flocks and humans and most of these strains originate from one large producer. Some strains appear connected to a larger number of human cases and also display spread between different farms,” said Dryselius.

“Just as in August, the increase in humans in October has been preceded by an increase in Campylobacter positive poultry flocks. Again, many of these positive flocks appear to originate from one and the same producer.”

Folkhalsomyndigheten has informed authorities about the situation to further investigate the cause of the spread of infection among broilers.

Link to raspberries in hepatitis A infections
Meanwhile, an outbreak of hepatitis A has been declared over with the suspected source of infection being frozen imported raspberries from Serbia.

A total of nine people fell ill with the first patient in July and the last in mid-September. They had the same type of hepatitis A virus, genotype IA, and lived in five different regions: Norrbotten, Västra Götaland, Stockholm, Uppsala and Södermanland. Those sick were aged 2 to 78 years old with six women and three men being affected.

During the summer, two cases of the outbreak strain in Denmark were also identified. Analysis of sampled berries has not been able to detect hepatitis A virus and no specific batch was identified.

Traceback investigations found two food chains where raspberries were purchased shared the same raspberry producer in Serbia.

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