November 21, 2014
CDC is collaborating with public health officials in several states and the U.S. Food and Drug Administration (FDA) to investigate a multistate outbreak of Salmonella Enteritidis infections. Results from this ongoing investigation indicate that bean sprouts produced by Wonton Foods, Inc. are the likely source of this outbreak.
Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA “fingerprinting” is performed on Salmonella bacteria isolated from ill persons using a technique called pulsed-field gel electrophoresis, or PFGE. PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. Two PFGE patterns are included this investigation. Both PFGE patterns are rarely reported to the PulseNet database. On average, less than 10 Salmonella bacteria with these PFGE patterns are reported to PulseNet each year.
As of November 21, 2014, a total of 63 persons infected with the outbreak strains have been reported from 10 states: Connecticut, Maine, Massachusetts, Montana, New Hampshire, New York, Ohio, Pennsylvania, Rhode Island, and Vermont. The one ill person from Montana traveled to the Eastern United States during the period when likely exposure occurred. Illness onset dates range from September 30, 2014 to November 8, 2014. Among 42 persons with available information, 11 (26%) have been hospitalized, and no deaths have been reported.
Investigation of the Outbreak
In interviews, ill persons answered questions about foods eaten and other exposures during the week before they became ill. Of 37 ill persons for whom information is known, 29 (78%) reported consuming bean sprouts or menu items containing bean sprouts in the week before they became ill. This proportion is significantly higher than results from a survey [PDF – 788 KB] of healthy persons in which 6% reported eating bean sprouts in the week before they were interviewed. Most ill persons reported consuming bean sprouts at Asian-style food service establishments.
In this investigation, state and local officials have identified five clusters of illnesses in three states: Massachusetts, Rhode Island, and Vermont. Among the ill persons who are part of these illness clusters, all reported consuming menu items that contained bean sprouts. Investigating clusters of illnesses can provide critical clues about the source of an outbreak. A cluster of illnesses is defined as more than one unrelated ill person (i.e., they do not know or live with each other) who report eating at the same restaurant location, attending a common event, or shopping at the same location of a grocery store before becoming ill. If several unrelated ill persons ate or shopped at the same location of a restaurant or store within several days of each other, it suggests that the contaminated food item was served or sold there. In addition, traceback of suspected food items to identify a common point of contamination may be facilitated by records kept at these locations.
State and local public health officials also performed traceback investigations on the source of bean sprouts for all five illness clusters as well as for several individual ill persons and reported the results of these investigations to FDA and CDC. Traceback from all of the establishments indicated that all received bean sprouts from Wonton Foods, Inc. of Brooklyn, New York. Although some restaurants also received bean sprouts from other suppliers, Wonton Foods, Inc. was the only supplier common to all of the restaurants and was the sole supplier of bean sprouts to at least two of the restaurants. The firm is cooperating with public health and agriculture officials and has reported that their last shipment of bean sprouts was on November 18, 2014. As of November 21, 2014, the firm has verbally agreed to voluntarily stop the production and sale of their bean sprouts while they take steps to prevent Salmonella contamination.
CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview them about foods they ate before they became ill. This ongoing investigation is rapidly evolving, and CDC will update the public when additional information is available.