CDC, multiple states, and the U.S. Food and Drug Administration (FDA) are investigating a multistate outbreak of Salmonella Poona infections linked to imported cucumbers from Mexico and distributed by Andrew & Williamson Fresh Produce.
Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet, the national subtyping network of public health and food regulatory agency laboratories, is coordinated by CDC. DNA “fingerprinting” is performed on Salmonella bacteria isolated from ill people by using a technique called pulsed-field gel electrophoresis, or PFGE. PulseNet manages a national database of these DNA “fingerprints” to identify possible outbreaks. Three DNA “fingerprints” (outbreak strains) are included in this investigation.
As of September 3, 2015, 285 people infected with the outbreak strains of Salmonella Poona have been reported from 27 states. The number of ill people reported from each state is as follows: Alaska (8), Arizona (60), Arkansas (6), California (51), Colorado (14), Idaho (8), Illinois (5), Kansas (1), Louisiana (3), Minnesota (12), Missouri (7), Montana (11), Nebraska (2), Nevada (7), New Mexico (15), New York (4), North Dakota (1), Ohio (2), Oklahoma (5), Oregon (3), South Carolina (6), Texas (9), Utah (30), Virginia (1), Washington (9), Wisconsin (2), and Wyoming (3).
Among people for whom information is available, illnesses started on dates ranging from July 3, 2015 to August 26, 2015. Ill people range in age from less than 1 year to 99, with a median age of 13. Fifty-four percent of ill people are children younger than 18 years. Fifty-seven percent of ill people are female. Among 160 people with available information, 53 (33%) report being hospitalized. One death has been reported from California.
This outbreak can be illustrated with a chart showing the number of people who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that occurred after August 14, 2015 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks. Please see the Timeline for Reporting Cases of Salmonella Infection for more details.
Investigation of the Outbreak
Epidemiologic, laboratory, and traceback investigations have identified imported cucumbers from Mexico and distributed by Andrew & Williamson Fresh Produce as a likely source of the infections in this outbreak. The investigation is ongoing.
State and local public health officials are interviewing ill people to obtain information about foods they might have eaten and other exposures in the week before their illness began. In interviews, ill people answered questions about foods eaten and other exposures in the week before their illness began. Fifty-eight (73%) of 80 people interviewed reported eating cucumbers. This proportion was significantly higher than results from a survey [PDF – 29 pages] of healthy people in which 55% reported eating cucumbers in the month of July in the week before they were interviewed.
In addition, numerous ill people were identified as part of illness clusters. An illness cluster is defined as two or more people who do not live in the same household who report eating at the same restaurant location, attending a common event, or shopping at the same location of a grocery store in the week before becoming ill. Investigating illness clusters can provide critical clues about the source of an outbreak. 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. Eleven illness clusters have been identified in seven states. In all of these clusters, interviews found that cucumbers were a food item eaten in common by ill people. Epidemiologic studies that compare foods eaten by both ill and well people are being conducted in two of these clusters. Preliminary results of these studies indicate that a food item containing cucumbers was associated with illness. Preliminary traceback information indicates that cucumbers eaten by ill people in these clusters were imported from Mexico and distributed by Andrew & Williamson Fresh Produce.
Several state health and agriculture departments are collecting leftover cucumbers from restaurants and grocery stores where ill people reported eating or shopping to test for the presence of Salmonella. The San Diego County Health and Human Services Agency isolated Salmonella from cucumbers collected during a visit to the Andrew & Williamson Fresh Produce facility. DNA “fingerprinting” is being conducted to determine the PFGE pattern of the Salmonella isolated from these cucumbers. Results of additional product testing will be reported when available.
Consultation with independent industry experts early in an outbreak investigation also can provide important clues to help focus the investigation on certain suspected foods. An industry consultation was held on August 26, 2015, with four independent experts from the produce industry to obtain information regarding fresh produce harvesting and distribution in the affected region. The consultants provided information regarding crop production and distribution practices that helped assess the plausibility of cucumbers and other produce items as possible outbreak sources.
On September 4, 2015, Andrew & Williamson Fresh Produce voluntarily recalled all cucumbers sold under the “Limited Edition” brand label during the period from August 1, 2015 through September 3, 2015 because they may be contaminated with Salmonella. The type of cucumber is often referred to as a “slicer” or “American” cucumber. It is dark green in color and typical length is 7 to 10 inches. In retail locations it is typically sold in a bulk display without any individual packaging or plastic wrapping. Limited Edition cucumbers were distributed in the states of Alaska, Arizona, Arkansas, California, Colorado, Florida, Idaho, Illinois, Kansas, Kentucky, Louisiana, Minnesota, Mississippi, Montana, Nevada, New Jersey, New Mexico, Oklahoma, Oregon, South Carolina, Texas, and Utah and reached customers through retail, food service companies, wholesalers, and brokers. Further distribution to other states may have occurred.
These cucumbers are shipped in a black, green, yellow, and craft colored carton which reads “Limited Edition Pole Grown Cucumbers.” Labeling on the cases of recalled cucumbers indicates the product was grown and packed by Rancho Don Juanito in Mexico. Domestically produced cucumbers are not believed to be involved in this outbreak.
CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory is conducting antibiotic resistance testing on clinical isolates collected from ill people infected with the outbreak strains; results will be reported when they become available.
This investigation is rapidly evolving. CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them. Updates will be provided when more information is available.