Danish officials have ended an investigation into an outbreak of E. coli that affected almost 40 people, but they are continuing to look at a Salmonella monophasic Typhimurium outbreak that has sickened almost 50 people.

For the E. coli outbreak, it was not possible to find the source of infection, officials report, but there was a suspected link to beef salami. In late 2018, Statens Serum Institut (SSI), the Danish Veterinary and Food Administration (Fødevarestyrelsen) and the National Food Institute jointly investigated the outbreak.

A total of 38 people, including 31 children younger than five years old, were infected with a specific type of Shiga toxin-producing E. coli (STEC) with the serotype O26:H11 from August to November 2018. Young children are one of the groups at higher risk of severe infections, life-threatening complications and death due to their immature immune systems.

However, authorities warned that due to mild symptoms the number of people affected may be higher than the almost 40 confirmed cases.

All patients had relatively mild symptoms of diarrhea and abdominal pain but one person was hospitalized. Cases were distributed across the country but most were in or around Copenhagen, Aarhus and Odense.

The outbreak strain causes relatively mild symptoms as it harbors the Shiga toxin (stx) 1a gene while hemolytic-uremic syndrome (HUS) is more often associated with strains that produce Stx2a. HUS is a severe complication of E. coli infection that can lead to kidney failure and death.

In November last year, that 26 confirmed patients’ ages were between less than 1 year old to 95 years old, with 19 being children younger than five. At that time, no other countries had confirmed cases related to the outbreak in Denmark.

Interviews with the patients or their parents did not reveal a common source of infection. However, most of them were linked with a daycare center or institutions with joint food arrangements, which received much of their food from larger catering wholesalers. based on studying purchases in the institutions involved it was found that beef salami was delivered to most of them.

Officials said beef salami is a known risk product for STEC and there were no other obvious risky items in purchased products. However, it was not possible to detect E. coli in samples from the suspected types of beef salami or to identify the source of infection using epidemiological methods.

From 2015 to 2017, O26:H11 was among the top four types of E. coli in terms of number of infections in the country. The other E. coli bacteria in the top spots were O157, O103 and O146.

The outbreak strain was resistant to the frontline antibiotics ampicillin, trimethoprim and sulfamethoxazole.

Salmonella illnesses linked to pork

Since mid-October 2018, 47 cases of a particular type of Salmonella monophasic Typhimurium have been reported to SSI. Salmonella monophasic Typhimurium (O: 4,5,12; H: i, -) is resistant to ampicillin, sulfamethoxazole and tetracycline.

Patients include 23 women and 24 men aged from birth to 97 years old, with 27 people needing hospitalization.

A case-control study involving 21 patients and 67 healthy controls pointed to a type of spiced sausage called medisterpølse as the source of the outbreak, but not all patients ate this product so it is possible there is other pork contaminated with Salmonella.

The outbreak was discovered in mid-November 2018. The type of Salmonella involved is known to come from pork.