Southeast Asian Imported Coriander had caused 40 cases of Shigellosis in Sweden


In late October 2015, Southeast Asian imported coriander has caused an outbreak of Shigellosis in Sweden. The severity of this outbreak had caused forty reported illnesses in three areas (twenty-nine from Vastra Gotaland, ten from Skane, and three from Halland). There was the same proportion of adult male and female who had fallen ill and no reported deaths.

Shigellosis is an acute bacterial infection caused by a group of Shigella bacteria. It is linked with “poor sanitation, contaminated food and water, and crowded living conditions”(Vyas, et al., 2014). Some symptoms include acute abdominal cramping, fever, bloody stools, watery diarrhea, and nausea (Vyas, et al., 2014). The severity of Shigellosis is mild as healthy individuals are able to surpass this illness with no chronic issues. However, the severity increases for malnourished children and immune-compromised individuals.

Coriander is a type of herb commonly used to complement a variety of foods and recipes as it adds a spicy flavor component that many find appealing. Therefore, it is commonly found in restaurant dishes where, in this case, has been the likely source of the illnesses reported in Vastra Gotaland and Skane. The Public Health Agency of Sweden had interviewed the people who were sick as part of their outbreak investigation and had found that there was a connection between different restaurants.

In addition to interviewing those who were sick, the Public Health agency of Sweden used “Whole-Genome Sequencing of the Shigella bacteria from the people who fell ill after visiting different restaurants” (Whitworth, 2015). Whole-genome sequencing is a type of molecular subtyping method used to reveal the complete genome of an organism in order to identify pathogens isolated from food samples (FDA, 2015). First, a sample is taken from a patient and is then cultivated in order to isolate bacterial DNA. After, the bacterial DNA found in the specimen becomes processed using an automated bench-top sequencing system. In other words, the bacterial DNA becomes processed in order to determine the order of nucleotides within its genome. Finally, this information can then be analyzed and compared to central data storage of known DNA bacterial sequences, in this case is the Shigella bacteria (Wang, Lecture Slide 18, 2015).

As a result from implementing a whole genome sequencing method, the Public Health Agency of Sweden did not detect the Shigella bacteria in any samples that were taken. Although the samples taken of the people ill showed close to identical bacterial strains, which suggests that their illness had most likely came from a common source. In addition, the coriander could not have been analyzed as it had disappeared from the marketplace before the outbreak became known. However, upon interviewing the people who were ill, it has been determined that coriander had been a common denominator found in the restaurant meals. This analysis has leaded the Public Health Agency of Sweden to conclude that the source of illness is the imported coriander from Southeast Asia.

This outbreak is a great example of the level of difficulty it is to find the cause of an outbreak when the cause is most likely an ingredient in a meal. Because the whole-genome sequencing indicate negative results for the presence of Shigellosis raises a lot of questions for the conclusions made by the Public Health Agency of Sweden. However, through their findings it is highly likely that the cause of the outbreak is from the coriander, but it is yet to be determined whether the illness is, indeed, Shigellosis. In order to ensure that similar outbreaks like this do not occur again, more stringent policies can be implemented to ensure that imported produce has come from the cleanest foreign companies.

Discussion Question: From what we have learned in class about the outbreak investigation method in Canada, would you agree with the Public Health Agency of Sweden to conclude that the source of illness had come from the Coriander? If not, what methods could they have further done to accurately determine the source of the Shigellosis bacteria?

References –
Witworth, J. (2015, November 25). Shigella outbreak traced to imported coriander. Retrieved November 26, 2015, from

Wang, S. (2015). Lecture Slide 18: Molecular Subtyping. FNH 413 Food Safety

Vyas, M. (2014, May 12). Shigellosis. Medline Plus. Retrieved November 26, 2015, from

FDA (2015, March 5). Whole Genome Sequencing (WGS) Program. U.S. Food & Drug Administration. Retrieved November 26, 2015, from