On the afternoon of May 13th, 2016, the US Centers for Disease Control and Prevention (CDC) released its “Final Update” to the February announcement of a multistate outbreak of Salmonella infections associated with consumption of alfalfa sprouts from Sweetwater Farms, which the CDC ultimately concluded was actually attributable to a single contaminated seed lot.
Recapping the Outbreak: Demographics and Related Information
Over the past three months, the CDC, the US Food and Drug Administration (FDA) and multiple states investigated a multistate outbreak involving 26 cases of Salmonella linked to “alfalfa sprouts from one contaminated seed lot.” That figure is double the number of reported cases in the initial outbreak report, released on February 23rd, which reported 13 people ill across four states.
25 of the 26 people infected in the outbreak tested positive for an outbreak strain of Salmonella Muenchen, while the remaining one case tested positive for Salmonella Kentucky. The CDC reports that the earliest date of onset was November 26, 2015, while the last case of Salmonella occurred on April 7th of this year.
Of the individuals who ultimately contracted one of the two outbreak strains of Salmonella, eight (31%) were hospitalized as a result of their illness; however, there were no fatal cases connected to the outbreak reported to public health authorities.
Twelve states had confirmed cases of the outbreak strains of Salmonella at the time of the CDC’s final update. The state that reported the most confirmed illnesses is Kentucky, which has confirmed five outbreak cases. Interestingly, no additional cases were reported in that state between the initial CDC announcement approximately three months ago and the final update published yesterday. States reporting three confirmed cases were Missouri, Oklahoma, and Pennsylvania, while Virginia, New York, New Jersey and Maryland each confirmed two cases. North Dakota, Ohio, and Washington were among the few states confirming one outbreak case.
Misguided Investigation: Identifying the Source of the Outbreak
Although the outbreak was initially thought to be tied to a single sprout grower, subsequent testing indicated that it was a seed lot, not a specific farm, that was responsible for the outbreak.
The investigation was conducted by the CDC in collaboration with the FDA and public health officials from multiple states, including officials from state departments of agriculture. During the nascent stages of the investigation, regulatory, state and local health officials in a number of states were able to isolate five restaurants where outbreak victims had dined shortly before falling ill and reported eating sprouts as part of their meals. The investigation concluded that Sweetwater Farms, located in Inman, Kansas, was the sprout supplier for all five locations. This conclusion was reached by both the FDA and the CDC.
In addition, the FDA and Kansas Department of Agriculture collected environmental samples from Sweetwater Farms which, when tested, yielded positive results for Salmonella. Unknown to the public, however, was the fact that the samples were positive for Salmonella Cubana and Salmonella Kentucky, not Salmonella Muenchen, the principal outbreak strain. The single case of Salmonella Kentucky was eventually linked to the farm, but the other 25 cases were definitively from another source or location.
The Kansas Department of Health and Environment issued a warning not to eat any alfalfa sprouts produced by Sweetwater Farms on February 19th, 2016, at which point the company withdrew its product from the market. Subsequently, on February 26th, the company informed the FDA that it was pulling all sprout products – not just alfalfa sprouts – from the retail market.
No More Sweetwater Farms Sprouts, Still More Salmonella: Further Investigating the Cause of the Outbreak
Even after Sweetwater Farms pulled all of its sprouts off of the market, new cases of Salmonella Muenchen continued to be reported by different states. This fact suggested that Sweetwater Farms was not the sole source of the outbreak, if it was a source at all.
Due to the continued increase in outbreak cases, the FDA had to continue its investigation. Further traceback investigations conducted by the agency indicated that other “sprouters” – farms or operations that grow sprouts for consumption – other than Sweetwater Farms produced and distributed the alfalfa sprouts the people who fell ill after the Sweetwater recall consumed before falling ill.
Upon further investigation, the FDA determined that Sweetwater Farms, along with the other sprouters that produced the sprouts that caused illnesses, had used the same seed lot to grow their sprouts. The FDA then contacted the seed supplier, who “called for the return of the contaminated seed lot from growers.” Although the FDA cannot by law identify the supplier by name, the agency has been assured that the sprouts are no longer on the market.
Regardless of the source, the FDA indicates that the outbreak appears to be over:
[The] FDA has been able to confirm that all domestic sprouters who received contaminated seeds either returned or destroyed the seeds, and the shelf life of all sprouts grown from this seed lot has expired. Therefore, no sprouts from the contaminated seed lot are expected to be on the market.