On May 13, 2021, FDA released a report on its investigation of the Salmonella Newport outbreak that caused more than 1,600 reported illnesses in the U.S. and Canada between June and October 2020. The agency worked with the U.S. Centers for Disease Control and Prevention, state partners, and Canadian officials (the Public Health Agency of Canada and the Canadian Food Inspection Agency) to investigate the outbreak, which was linked through epidemiology and traceback to whole red onions supplied by Thomson International Inc., headquartered in Bakersfield, Calif., with additional locations in Holtville, Calif.
The outbreak is the largest Salmonella foodborne illness outbreak in more than a decade. The FDA report includes an overview of the traceback investigation, subsequent on-site interviews, visual observations of the growing fields, environmental sampling, and various factors that potentially contributed to the contamination.
The report identified several potential contributing factors to the outbreak in red onions:
- Potentially contaminated sources of irrigation water;
- Sheep grazing on adjacent land;
- Signs of animal intrusion, including scat (fecal droppings), and large flocks of birds that may spread contamination; and
- Food contact surfaces that had not been inspected, maintained, or cleaned as frequently as necessary to protect against the contamination of produce.
In sampling conducted in Holtville, FDA found Salmonella Newport in 10 water (irrigation, seepage, and drainage) subsamples and in one sediment subsample; however, the whole genome sequencing of these samples did not match the outbreak strain.
Although a conclusive root cause could not be identified, one leading hypothesis is that contaminated irrigation water used in a growing field in Holtville may have led to contamination of the onions.
In light of this report, FDA encourages all farms to:
- Assess growing operations to ensure implementation of appropriate science and risk-based preventive measures, including applicable provisions of the Food Safety Modernization Act Produce Safety Rule and good agricultural practices;
- Implement industry-led root-cause analyses to determine how the contamination likely occurred when pathogens are identified through pre-harvest or post-harvest testing of produce or microbiological surveys;
- Be aware of and consider the risks that may be posed by adjacent and nearby land uses, especially as it relates to the presence of livestock and the interface between farmland, rangeland, irrigation water, and other agricultural areas;
- Consider additional tools such as pre-harvest and/or post-harvest sampling and testing of products to help inform the risk assessment and clarify the need for specific prevention measures; and
- Improve traceability by increasing digitization, interoperability, and standardization of traceability records; and
- Follow good agricultural practices to maintain and protect the quality of water sources.
Thomson International Inc. cooperated with FDA throughout the investigation and is continuing to engage with the agency regarding its findings and recommendations.