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Shigella outbreak traced to imported coriander

By Joe Whitworth+

25-Nov-2015

Fresh coriander from Southeast Asia was identified as the likely source. Picture: Istock/MarenWischnewski
Fresh coriander from Southeast Asia was identified as the likely source. Picture: Istock/MarenWischnewski

Fresh coriander was the probable cause of an outbreak of shigellosis which sickened more than 40 people in Sweden.

During 16 October – 1 November, 42 cases of shigellosis were reported. A total of 29 came from Västra Götaland, ten from Skåne and three from Halland.

Of the information available the illnesses were of equal proportion between men and women all of them adults and there were no deaths.

Coriander from Southeast Asia

Outbreak investigation identified fresh coriander imported from Southeast Asia as the likely source of infection. The coriander was used as an ingredient in a meal.

This was done by a cohort study among guests at one of the restaurants. The coriander was also the common denominator used at all the restaurants where cases had eaten.

In interviews with the people who were sick there was a connection to different restaurants in Skåne and Västra Götaland.

Livsmedelsverket (National Food Agency of Sweden) told FoodQualityNews it worked with Folkhälsomyndigheten (the public health agency of Sweden) during the investigation.

There was a large outbreak in 2008 with 140 cases which had eaten at a restaurant and there are 300-600 reported cases every year in Sweden, most of them imported.

Traceback investigation

Folkhälsomyndigheten used whole genome sequencing - analysis of the entire genome - of Shigella bacteria from people who fell ill after visiting different restaurants.

Livsmedelsverket analysis did not detect Shigella in any of the samples. The coriander could not be analysed because it had already gone from the marketplace when the outbreak become known.

Analyses of Shigella of people who had been ill showed that the bacterial strains were identical, which means that a common source of infection was very likely.

Folkhälsomyndigheten told us the implicated coriander cannot be sold, until proven safe to consume but no other coriander is under restriction.

Shigellosis is caused by Shigella bacteria it can typically take two to three days after becoming infected to get sick or up to a week.

Symptoms of the disease include diarrhea, abdominal pain, vomiting, and often fever. It requires only a few bacteria to give rise to infection.

Shigellosis is fifth in the most commonly identified and reported enteric infection in the EU/EEA area, according to the latest ECDC annual epidemiological report 2014 on food-and waterborne diseases and zoonoses.

In 2012, 7,336 confirmed cases of Shigella infection were reported from 28 EU/EEA countries.

Bulgaria (with 10.8 cases per 100,000) and Slovakia (with 9.9 cases per 100,000) continued to report the highest confirmed rates of the EU/EEA countries.

Sweden, Norway, the Netherlands and the UK reported confirmed rates of around 3 per 100,000.

Shigellosis is not a zoonosis; humans are the only known reservoir. Prevention of infection and control relies on good personal and environmental hygiene practices to prevent faecal – oral transmission, said ECDC.

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