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BACKGROUND: Salmonella causes 1.2 million infections and 380 deaths each year in the United States. On May 6, 2014, PulseNet, the national molecular subtyping network for foodborne disease surveillance, detected a multistate cluster of Salmonella Newport infections with an indistinguishable pulse-field electrophoresis (PFGE) pattern. This strain of Salmonella Newport had never been seen before in PulseNet. US states, the Food and Drug Administration (FDA), Canada health and regulatory officials, and CDC investigated to identify the source and prevent additional illnesses.
METHODS: A case was defined as an infection with an outbreak strain with illness onset from January 1, 2014 to July 22, 2014. We conducted single interviewer open-ended interviews to identify common travel, restaurant and food exposures in the week prior to illness onset, administered supplemental questionnaires to refine hypotheses, collected products for testing, and performed traceback investigations.
RESULTS: We identified 31 case-patients in 16 states; 22% (5/23) were hospitalized. Ill persons ranged in age from 1 year to 81 years, with a median age of 48 years. Sixty-one percent of ill persons were female. Ninety percent (19/21) of case-patients reported eating chia seeds or powder; 79% (15/19) of those specifically reported eating chia seed powder of variable brand names. Traceback identified a Canadian firm as the common supplier for the sprouted chia seed powder. Multiple products containing sprouted chia seed powder from this firm were recalled and FDA denied admission of these products into the United States until testing could confirm the products were no longer contaminated. During the investigation, testing conducted by state public health laboratories of leftover chia-containing products provided by ill persons isolated the outbreak strain of Salmonella Newport as well as two more rare Salmonella strains (Hartford and Oranienburg) that also caused illnesses; these additional strains were included in the outbreak.
CONCLUSIONS: Epidemiologic, traceback, and laboratory evidence identified sprouted chia seed powder processed at a single firm as the outbreak source. Although sprouted chia seeds are a novel Salmonella outbreak vehicle, this investigation highlights the well-documented risks for foodborne illness associated with the sprouting process. Firms choosing to produce sprouted seed products should follow available guidance to reduce the risk of bacterial contamination.