While an Idaho grower refused to recall sprouts implicated in a multistate outbreak of Salmonella, the Centers for Disease Control and Prevention released its report Tuesday on the 21 people whose illnesses may have been caused by those sprouts.
As of Monday, the CDC said, nine people in Washington state, seven people in Montana, three in Idaho, and one in both North Dakota and New Jersey have been stricken with the same strain of Salmonella Enteritidis.
The case patients range from 12 to 77 years of age. Among the 10 people with available information, three have been hospitalized because of the severity of their symptoms.
Epidemiological investigations by local, state and federal public health agencies linked the outbreak to alfalfa sprouts and spicy sprouts (a mix of alfalfa, clover and radish sprouts) grown by Evergreen Produce in Moyie, Idaho.
Meanwhile, the U.S. Food and Drug Administration provided more information about the investigations. In an email response to Food Safety News, the FDA said the initial exposure information from the affected states on 13 of the case patients showed that nine (69 percent) reported eating alfalfa sprouts during the week before the onset of their symptoms.
The typical amount of alfalfa sprouts consumption in the Northwest, based on Oregon data, is just 4.8 percent (in the United States as a whole, it is 4.4 percent) — so the 69 percent exposure rate is significant epidemiological evidence that explains why the FDA reported Monday that “the strain of S. Enteritidis is rarely seen at this frequency.”
In an effort to prevent the possibility of further illnesses from Evergreen Produce brand alfalfa sprouts and spicy sprouts, the FDA issued a consumer advisory warning people not to eat them.
The agency did this as Nadine Scharf, owner of the Idaho sprouts growing operation, refused to recall her potentially contaminated product in the absence of “concrete proof” that the sprouts were making some customers sick.
This isn’t the first time a food producer has rejected epidemiologic evidence, and foodborne outbreak investigations are often as misunderstood by the food industry as they are by the public.
When tests of patients’ stool specimens reveal they are all infected with the same pathogen, public health investigators, through detailed interviews, first identify specific foods the case patients had in common. Then traceback investigations determine whether the suspect foods had a common origin. Lab tests on food samples can confirm that epidemiological and traceback evidence, but often the contaminated food is long gone — consumed or discarded — so there never is a “smoking gun.” Nevertheless, epidemiologic evidence is as crucial as microbiologic evidence in tracking down suspects.
Raw produce can present a challenge, however, especially when it comes to salads, salsas, guacamoles or similar mixed dishes, and patients can’t recall all the ingredients. That was the case in 2008, when a Salmonella outbreak was initially attributed to tomatoes but the culprit turned out to be contaminated hot peppers.
Sprouts are often on the list of possible suspects — since 1996 there have been at least 30 reported foodborne illness outbreaks in the United States associated with sprouts, the CDC notes.
In its report Tuesday, the CDC repeated the FDA’s warning that potentially contaminated sprouts from Evergreen Produce may still be in grocery stores and in consumers’ homes, and recommended that they be disposed of in a closed plastic bag placed in a sealed trash can to prevent people or animals from eating them.
The FDA, which now has the authority to impose a mandatory recall of Evergreen Produce sprouts but has not taken that step, told Food Safety News it is “exploring all options under the law to ensure the product is taken off the market as quickly and expeditiously as possible.”
Centers for Disease Control and Prevention outbreak map