Though the investigation into a Salmonella Reading outbreak with several unusual features and linked to raw turkey products ended in April, the outbreak strain has become widespread in the turkey production industry, and cases continue to be reported, according to a new report today.

Public health officials from the US Centers for Disease Control and Prevention and health partners from several states and the District of Columbia fleshed out more details about the investigation and the unique outbreak in the latest issue of Morbidity and Mortality Weekly Report (MMWR). Given the lingering threat, they also urged the industry and consumers to continue taking steps to reduce contamination.

Cases first noted in early 2018

Minnesota health officials first identified the outbreak in January 2018, based on genetic analysis of samples from four patients infected with Salmonella Reading, and their investigation pointed to different types of raw turkey exposure. In addition, lab analysis found the outbreak strain in a sample from retail ground turkey.

PulseNet, the national subtyping system, identified other illnesses, including two subclusters in which sick people ate at a common event—one in the District of Columbia and one in Iowa. Taken together, 152 illnesses were identified as part of the clusters, and investigations found that whole turkey and boneless roast turkey that was not handled or prepared properly were linked to the two events.

Over the course of the investigation, 356 cases in 42 states and the District of Columbia were found. Of those, 132 patients were hospitalized, and 1 died.

Health officials found that, of 198 people who were interviewed, 67% had direct or indirect contact with turkey in the week before they got sick, which ranged from preparing or eating turkey to serving pets raw food containing turkey to working at a turkey processor.

Outbreak strain throughout industry

Meanwhile, lab tests on raw turkey and from slaughtering operations and processors yielded the outbreak strain across several brands and types of raw turkey products, but no commercial connections or common source materials were found, suggesting that the Salmonella Reading outbreak strain was present throughout the turkey industry, in live birds and in raw food products.

In July 2018, the CDC and the US Department of Agriculture's Food Safety and Inspection Service (FSIS) approached turkey industry leaders to discuss what steps they could take to reduce contamination. "This was the first time that CDC and FSIS engaged an industry group rather than a specific company during an outbreak, a step taken because no single product or common supplier was identified," the group wrote.

Later that month, the CDC posted its first investigation notice about the outbreak, a new communication tool designed to notify consumers and partners for situations when no specific source has been found but when steps are needed to identify the cause and prevent more illnesses.

The authors said the outbreak strain might have been introduced to the turkey supply chain and spread to many establishments and products before Minnesota officials identified the first four cases and PulseNet identified a multistate outbreak.

Interventions to curb Salmonella Reading contamination need to target all parts of the poultry supply chain, the authors write. And though eliminating it from flocks is a challenge, the responsibility for developing strategies to reduce contamination begins with the industry, they add.

What's more, the findings from the two large clusters underscore the importance of reminding consumers about proper handling and cooking procedures, the experts note.

See also:

Nov 22 MMWR report