More than 40 people are sick and almost a third have needed hospital treatment as part of a foodborne Shigella outbreak in Denmark.

From the end of August, 42 people have been registered with shigellosis in the country.

The outbreak is being investigated to try to pinpoint the source of infection and help stop it with experts doing final traceback investigations ahead of plans to reveal results next week.

From Aug. 25 to Sept. 10, 42 cases of shigellosis were reported to the Statens Serum Institut (SSI).

Patients are 26 women and 15 men aged 0 to 75 years old. The median age is 29 years old. A total of 13 people have been hospitalized. Most live in Hovestaden, while four cases have been reported in Sjælland and two in Midtjylland.

Investigating to find the source
Interviews with those affected showed they had not been traveling in the period before they became ill. Shigella is not widespread in Denmark and is most often acquired because of travel abroad.

Shigella sonnei has been isolated from 10 outbreak patients and whole genome sequencing shows closely related isolates. The other 31 patients are PCR-positive for the ipaH gene, which is a marker for all Shigella species and enteroinvasive E. coli.

Previous outbreaks in Denmark include one in 2007, when more than 210 people became ill from eating contaminated imported baby corn. There were also 12 cases in Queensland, Australia. Infections were linked to a common baby corn packing house in Thailand.

Another outbreak in 2009 involved 10 people and was traced to fresh, raw sugar peas (sugar snaps) imported from Kenya. Later that year, Norwegian officials identified four illnesses and five suspected cases that were linked.

Most people infected with Shigella develop diarrhea, fever, and stomach cramps starting a day or two after they are exposed to the bacteria. Shigellosis usually resolves in five to seven days but some people may experience symptoms from a few days to four or more weeks. People who are in poor health or who have weakened immune systems are more likely to get sick for a longer period of time if they have shigellosis.

Meanwhile, a Hepatitis A outbreak investigation is still ongoing with no firm hypothesis of the source. It now includes 16 patients, up from 14 people aged 17 to 63 in the previous update. Eleven people have needed hospital treatment. Interviews have shown patients have not been traveling, do not know each other and they had not participated in joint events.

A Salmonella Strathcona outbreak that affected 25 people seems to be over but the source is not known. The outbreak of Salmonella Kasenyi is over with 11 cases but no source could be identified.