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Background Frozen foods have rarely been linked to Listeria monocytogenes illness. We describe an outbreak investigation prompted by both hospital clustering of illnesses and product testing. Methods We identified outbreak-associated listeriosis cases using whole-genome sequencing (WGS), product testing results, and epidemiologic linkage to cases in the same Kansas hospital. We reviewed hospital medical and dietary records, product invoices, and molecular subtyping results. Federal and state officials tested product and environmental samples for L. monocytogenes. Results Kansas officials were investigating 5 cases of listeriosis at a single hospital when, simultaneously, unrelated sampling for a study in South Carolina identified L. monocytogenes in Company A ice cream products made in Texas. Isolates from 4 patients and Company A products were closely related by WGS, and the 4 patients with known exposures had consumed milkshakes made with Company A ice cream while hospitalized. Further testing identified L. monocytogenes in ice cream produced in a second Company A production facility in Oklahoma; these isolates were closely related by WGS to those from 5 patients in 3 other states. These 10 illnesses, involving 3 deaths, occurred from 2010 through 2015. Company A ultimately recalled all products. Conclusions In this US outbreak of listeriosis linked to a widely distributed brand of ice cream, WGS and product sampling helped link cases spanning 5 years to 2 production facilities, indicating longstanding contamination. Comprehensive sanitation controls and environmental and product testing for L. monocytogenes with regulatory oversight should be implemented for ice cream production.

Background Nontyphoidal Salmonella causes ~1 million food-borne infections annually in the United States. We began investigating a multistate outbreak of Salmonella serotype Agona infections in April 2011. Methods A case was defined as infection with the outbreak strain of Salmonella Agona occurring between 1 January and 25 August 2011. We developed hypotheses through iterative interviews. Product distribution analyses and traceback investigations were conducted. The Food and Drug Administration (FDA) tested papayas from Mexico for Salmonella. Results We identified 106 case patients from 25 states. Their median age was 21 years (range, 1-91). Thirty-nine of 61 case patients (64%) reported Hispanic/Latino ethnicity; 11 of 65 (17%) travelled to Mexico before illness. Thirty-two of 56 case patients (57%) reported papaya consumption. Distribution analyses revealed that three firms, including Distributor A, distributed papaya to geographic areas that aligned with both the location and timing of illnesses. Traceback of papayas purchased by ill persons in four states identified Distributor A as the common supplier. FDA testing isolated the outbreak strain from a papaya sample collected at distributor A and from another sample collected at the US-Mexico border, destined for distributor A. FDA isolated Salmonella species from 62 of 388 papaya import samples (16%). The investigation led to a recall of fresh, whole papayas from Distributor A and an FDA import alert for all papayas from Mexico. Conclusions This is the first reported Salmonella outbreak in the United States linked to fresh, whole papayas. The outbreak highlights important issues regarding the safety of imported produce.

SUMMARYDuring June–August 2013, 25 US states reported 631 cyclosporiasis cases including Nebraska and Iowa where a regional investigation implicated common-source imported salad mix served in two chain restaurants. At least two common-origin growing fields were likely sources of contaminated romaine lettuce. Using producer- and distributor-provided data, we conducted a grower-specific traceforward investigation to reveal exposures of ill US residents elsewhere who reported symptom onset during 11 June–1 July 2013, the time period established in the Nebraska and Iowa investigation. Romaine lettuce shipped on 2–6 June from one of these Mexico-origin growing fields likely caused cyclosporiasis in 78 persons reporting illness onsets from 11 June to 1 July in Nebraska, Texas, and Florida. Nationwide, 97% (314/324) of persons confirmed with cyclosporiasis with symptom onset from 11 June to 1 July 2013 resided in 11 central and eastern US states receiving approximately two-thirds of romaine lettuce from this field. This grower's production practices should be investigated to determine potential sources of contamination and to develop recommendations to prevent future illnesses.

Cholera caused by toxigenic Vibrio cholerae, serogroup O1, serotype Ogawa, biotype El Tor, was confirmed on October 21, 2010, in Haiti and on October 31, 2010, in the Dominican Republic. These countries are on the island of Hispaniola. During October 21, 2010–April 4, 2011, >275,000 cholera cases and >4,700 deaths were reported from Hispaniola. Of these cases, 840 culture-confirmed cases and 10 deaths were reported from the Dominican Republic. Illness caused by toxigenic V. cholerae O1 has been documented in the United States since 1832. During 1965–1991, an average of 5 cases per year were reported. During the Latin American cholera epidemic that started in 1991, the number of cholera cases in the United States increased because of importation of cases related to the epidemic to an average of 53 cases per year during 1992–1994 (1,2). As the Latin American epidemic waned, during 1995–2000, the average annual case count decreased to 10 (3). During 2000–2010, the average number of cases was 6, and 57% of case-patients had traveled internationally (4). This experience raised concern that a dramatic increase in US cholera cases could result from the Hispaniola epidemic. In the United States, cholera is confirmed by identification of toxigenic V. cholerae serogroup O1 or O139 or by serologic evidence of infection in a patient with diarrhea and an epidemiologic link to a culture-confirmed case. Since 2000, suspected V. cholerae isolates have been sent by state public health laboratories to the Centers for Disease Control and Prevention (CDC) for confirmation and characterization. We summarize characteristics of confirmed US cases associated with the Hispaniola epidemic that were reported to the CDC Cholera and Other Vibrio Illness Surveillance System, a national database of all laboratory-confirmed cholera and vibriosis cases. For each case of cholera, state and local health officials submit a Cholera and Other Vibrio Illness Surveillance System report form that contains demographic, clinical, and epidemiologic information, including selected food and water exposures associated with cholera, travel history, and vaccination status.

BACKGROUND Although new pathogen-vehicle combinations are increasingly being identified in produce-related disease outbreaks, fresh produce is a rarely recognized vehicle for listeriosis. We investigated a nationwide listeriosis outbreak that occurred in the United States during 2011. METHODS We defined an outbreak-related case as a laboratory-confirmed infection with any of five outbreak-related subtypes of Listeria monocytogenes isolated during the period from August 1 through October 31, 2011. Multistate epidemiologic, trace-back, and environmental investigations were conducted, and outbreak-related cases were compared with sporadic cases reported previously to the Listeria Initiative, an enhanced surveillance system that routinely collects detailed information about U.S. cases of listeriosis. RESULTS We identified 147 outbreak-related cases in 28 states. The majority of patients (127 of 147, 86%) were 60 years of age or older. Seven infections among pregnant women and newborns and one related miscarriage were reported. Of 145 patients for whom information about hospitalization was available, 143 (99%) were hospitalized. Thirty-three of the 147 patients (22%) died. Patients with outbreak-related illness were significantly more likely to have eaten cantaloupe than were patients 60 years of age or older with sporadic illness (odds ratio, 8.5; 95% confidence interval, 1.3 to ∞). Cantaloupe and environmental samples collected during the investigation yielded isolates matching all five outbreak-related subtypes, confirming that whole cantaloupe produced by a single Colorado farm was the outbreak source. Unsanitary conditions identified in the processing facility operated by the farm probably resulted in contamination of cantaloupes with L. monocytogenes. CONCLUSIONS Raw produce, including cantaloupe, can serve as a vehicle for listeriosis. This outbreak highlights the importance of preventing produce contamination within farm and processing environments.