Factors Potentially Contributing to the Contamination of Packaged Leafy Greens Implicated in the Outbreak of Salmonella Typhimurium During the Summer of 2021
In July and August of 2021, the U.S. Food and Drug Administration (FDA), Centers for Disease Control and Prevention (CDC), and state partners conducted an outbreak investigation into a multistate outbreak of Salmonella Typhimurium linked to packaged leafy greens produced at a Controlled Environment Agriculture (CEA) indoor hydroponic operation.
Total Illnesses: 31
First illness onset: June 10, 2021
Last illness onset: August 18, 2021
States with Cases: IL (18), MI (1), PA (2) WI (10)
The outbreak response investigation found:
- The outbreak was associated with the consumption of packaged leafy greens from the firm’s CEA indoor hydroponic operation; 26 of 27 (96%) patients reported consuming any leafy greens prior to illness onset, with 20 of 24 cases reporting consumption of prepackaged salads. This firm’s products were named specifically in 14 cases.
- This outbreak was caused by Salmonella Typhimurium as determined by whole genome sequencing (WGS) analysis. The Salmonella Typhimurium isolates from ill consumers were closely related genetically; however, there were no product isolates for comparison.
- Loyalty card data was received for nine cases. The information identified a common brand of packaged salads and the traceback investigation determined all of the points-of-service (POS) were supplied by the same hydroponic operation owned and operated by this firm. The firm’s salad products purchased by ill consumers were confirmed to be produced at the firm’s hydroponic operation.
FDA conducted an on-site produce safety investigation of the firm’s CEA operation, as part of the outbreak investigation.
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 Throughout this document the term “firm” is used to represent the business entity, while the term “operation” refers to the farm location.