Multistate product traceforward investigation to link imported romaine lettuce to a US cyclosporiasis outbreak – Nebraska, Texas, and Florida, June–August 2013

Abstract

During 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.

The Hurdle Approach–A Holistic Concept for Controlling Food Safety Risks Associated With Pathogenic Bacterial Contamination of Leafy Green Vegetables. A Review

“…Identification of the offending produce enables subsequent trace-back investigations, which can identify potential suspects responsible for the original contamination further upstream within the value network (Horby et al, 2003; Slayton et al, 2013; Public Health England (PHE), 2015; Buss et al, 2016a,b). However, there have only been two outbreaks for which bacteria matching the outbreak strain have been isolated from environmental samples on, or in close proximity to, suspected farms (CDC, 2006; Grant et al, 2008; Söderström et al, 2008).…”

Emerging infections—an increasingly important topic: review by the Emerging Infections Task Force

“…The source was traced to a single producer of sprouts in Germany who used seeds produced and contaminated in Egypt [8]. A similar outbreak was reported from the United Kingdom, presumably from handling raw leeks and potatoes [30]. Multistate outbreaks in the United States of Cyclospora cayetanensis were linked to imported lettuce from a single manufacturer [31].…”

Regional investigation of a cyclosporiasis outbreak linked to imported romaine lettuce – Nebraska and Iowa, June–August 2013

“…Our investigation's success resulted from correlating occurrence of illnesses (or lack therefore) to product distribution rather than points-of-service. By implicating producer A-supplied romaine lettuce, we enabled product traceforward that further linked this source to exposures of additional ill persons beyond Midwest chain A/B restaurants, including points-of-service supplied by other distribution channels in Florida, Texas, and Nebraska [10]. A report from Texas also linked at least 25 cases during 2013 to imported cilantro [3].…”