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Concurrent Cryptosporidium parvum outbreaks: molecular characterisation supporting epidemiological investigations leads to identification of different implicated food items, Sweden, 2019
- Ioana Bujila1 , Marie Jansson-Mörk2,3 , Joanna Nederby-Öhd4 , Anette Hansen2 , Mats Lindblad5 , Karolina Fischerstöm4 , Matilda Bragd6 , Ingela Hall6 , Nilla Lindroos7 , Caroline Rönnberg1,8 , Moa Rehn2 , Jessica Beser1,9
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View Affiliations Hide AffiliationsAffiliations: 1 Department of Microbiology, Public Health Agency of Sweden, Solna, Sweden 2 Department of Communicable Disease Control and Health Protection, Public Health Agency of Sweden, Solna, Sweden 3 ECDC Fellowship Programme, Field Epidemiology path (EPIET), European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden 4 Department of Communicable Disease Control and Prevention, Region Stockholm, Stockholm, Sweden 5 Swedish Food Agency, Uppsala, Sweden 6 Department of Communicable Disease Control and Prevention, Region Jönköping, Jönköping, Sweden 7 Department of Communicable Disease Control and Prevention, Region Halland, Halmstad, Sweden 8 Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden 9 ECDC Fellowship Programme, Public Health Microbiology path (EUPHEM), European Centre for Disease Prevention and Control (ECDC), Stockholm, SwedenJessica BeserJessica.Beser ecdc.europa.eu
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Citation style for this article: Bujila Ioana, Jansson-Mörk Marie, Nederby-Öhd Joanna, Hansen Anette, Lindblad Mats, Fischerstöm Karolina, Bragd Matilda, Hall Ingela, Lindroos Nilla, Rönnberg Caroline, Rehn Moa, Beser Jessica. Concurrent Cryptosporidium parvum outbreaks: molecular characterisation supporting epidemiological investigations leads to identification of different implicated food items, Sweden, 2019. Euro Surveill. 2025;30(26):pii=2400643. https://doi.org/10.2807/1560-7917.ES.2025.30.26.2400643 Received: 27 Sept 2024; Accepted: 15 Jan 2025
Abstract
In Sweden, an increase in the number of notified cases of cryptosporidiosis was observed 1 October–31 December 2019 (462 domestic cases). Although a single national outbreak was initially suspected, molecular and epidemiological analyses revealed two concurrent national outbreaks and three local outbreaks. Cryptosporidium parvum subtype IIdA22G1c and IIdA24G1 were identified as the cause of the national outbreaks and subtype IIdA20G1e and IIdA21G1 as the cause of the local outbreaks. A case-case study comparing exposures in IIdA22G1c to IIdA24G1 revealed that cases with subtype IIdA22G1c (n = 48) were associated with consumption of a fresh fruit-and-vegetable juice (adjusted odds ratio (aOR) = 17; 95% confidence interval (CI): 1.8–169; p = 0.002). In the local outbreaks with subtype IIdA20G1e and IIdA21G1, cohort studies suggested that cases were associated with consumption of salads. Several coinciding outbreaks with different C. parvum subtypes explained the increase of cryptosporidiosis, and molecular typing was crucial in guiding relevant cross-disciplinary collaboration.

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