Apr 7, 2021
FDA takes steps to advance the safety of leafy greens

The U.S. Food and Drug Administration announced April 6 it is taking two important steps to advance the safety of leafy greens.

The first is the release of a report on the investigation into the Fall 2020 outbreak of E. coli O157:H7 illnesses linked to the consumption of leafy greens. The report describes findings from the investigation, as well as trends key to understanding leafy greens outbreaks linked to the California Central Coast growing region (encompassing the Salinas Valley and Santa Maria growing areas) that have occurred every fall since 2017.

In addition, the FDA is also releasing an updated version of the Leafy Green Shiga-toxin producing E. coli (STEC) Action Plan, reaffirming the need for collaborative action to improve the safety of leafy greens, and building on the work accomplished in 2020.

Investigation report

Between August and December 2020, the FDA and multiple state and federal partners were involved in an investigation into an outbreak of E. coliO157:H7 illnesses associated with the consumption of leafy greens. The outbreak caused 40 illnesses across 19 states, resulting in 20 hospitalizations, including four cases of hemolytic uremic syndrome (HUS), a type of kidney failure.

During the traceback investigation the outbreak was linked via whole genome sequencing (WGS) to outbreaks associated with the consumption of leafy greens grown in California’s Central Coast growing areas that have occurred every fall since 2017.  Using the information learned during traceback, along with data collected in response to previous outbreaks, the FDA was able to narrow the scope of the investigation to fields in the Salinas Valley growing area of California.

The FDA, in collaboration with California state partners, investigated several farms with fields linked through traceback; we identified the outbreak strain in one cattle feces composite sample taken alongside a road approximately 1.3 miles upslope from a produce farm with multiple fields linked to the outbreak through traceback. In addition, several other samples tested positive for other STEC strains, including E. coli O157:H7.  While no direct source or route of contamination was identified, the investigation provided insights into potential sources of contamination, including livestock activities on adjacent land.

Reoccurring outbreak strain, growing region, and concerns with the potential impacts of adjacent lands

The FDA analyzed outbreaks that had occurred each fall since 2017 in light of the findings of this investigation and found three key trends in the contamination of leafy greens by E. coli O157:H7 in recent years: a reoccurring strain, reoccurring region and reoccurring concerns with the potential impacts of  adjacent lands. This reoccurring pathogenic E. coli strain therefore appears to be a reasonably foreseeable hazard in the California Central Coast leafy greens growing region, and specifically of concern in the South Monterey County area of the Salinas Valley growing area.

Farms subject to the FSMA Produce Safety Rule are required to take all measures reasonably necessary to identify, and not harvest,  produce that is likely to be contaminated with a known or reasonably foreseeable hazard.


The FDA recommends that the agricultural community in the California Central Coast growing region work to identify where this reoccurring strain of pathogenic E.coli is persisting and the likely routes of leafy green contamination with STECs.  In the report, the  FDA encourages producers in the Central Coast of California growing region to participate in the California Longitudinal Study, and in the locally-led, locally-convened California Agricultural Neighbors (CAN) workgroup. In addition, when pathogens are identified through microbiological surveys, pre-harvest or post-harvest testing, we recommend growers implement industry-led root cause analyses to determine how the contamination likely occurred and then implement appropriate prevention and verification measures.

Leafy Greens STEC Action Plan

The FDA recognizes that more work is needed from all leafy greens stakeholders to advance the vision outlined in the Leafy Green STEC Action Plan. Originally released in March 2020, the action plan was designed to foster a more urgent and collaborative approach to preventing leafy greens outbreaks caused by STEC.  Progress made to date includes the launch of  the California Longitudinal Study, the development of an efficacy protocol to aid in the development and registration of antimicrobial treatments for pre-harvest agricultural water, and several  focused inspections, follow-up investigations, sampling assignments, and critical steps taken to advance traceability of leafy greens.

Building on this work, the FDA released an updated version of the Leafy Green STEC Action Plan today which reaffirms our commitment to advancing leafy greens safety. The updated plan includes a renewed emphasis on actions to prevent contamination stemming from activities on adjacent land, announces new actions that build on the accomplishments and learnings from the 2020 plan, and renews our commitment to  completing certain actions that were difficult to accomplish in 2020 due to challenges presented by the COVID-19 pandemic.

Shared responsibility

We know that we cannot fix the issue of leafy green contamination on our own. Recognizing the interconnection between people, animals, plants, and their shared environment, we strongly encourage collaboration to address the issues contributing to produce contamination. Industry leadership, along with collaboration among growers, processors, retailers, state partners and the broader agricultural community, is critical to establishing needed prevention measures and preventing foodborne illness.

For more information:  E. coli and Foodborne Illness

California Department of Food and Agriculture responds

As the U.S. Food and Drug Administration (FDA) announced a constituent update on April 6 – FDA Takes Two Important Steps to Advance the Safety of Leafy Greens – farmers, researchers and regulators are urged to collaborate on many fronts to understand and prevent foodborne outbreaks of Shiga toxin-producing E. coli (STEC) infections in the United States with a confirmed or suspected link to leafy greens.

The FDA’s Leafy Greens STEC Action Plan outlines a number of progressive food safety initiatives. California partners are working with the FDA on several efforts within this action plan – outlined in a California Initiatives Roadmap – to address knowledge gaps, engage in prevention measures, and conduct response activities. One research study the California Department of Food and Agriculture (CDFA) is helping coordinate in this effort is a California Longitudinal Study (CALS), led by the FDA Center for Food Safety and Applied Nutrition, the UC Davis Western Center for Food Safety, and an industry advisory group.

CALS is a multi-year study that is seeking farmers and ranchers along California’s Central Coast to allow researchers to collect and examine samples from the environment – including adjacent land, well and surface waters, and soil inputs that include compost, dust and animal fecal samples. This longitudinal approach serves as a model to offer an adaptive research strategy, perform research on a large geographic area to better understand underlying causes of contamination in the production environment, and provide a scientific basis for preventive recommendations.

To encourage participation in the CALS study, CDFA Secretary Karen Ross released a letter to industry partners, saying: “Food safety is a shared responsibility. I appreciate those who have been leaders for their industry – early adopters who have come forward and are working to find solutions to a recurring problem by collaborating with the nation’s best scientists. It shows a commitment to food safety and California agriculture. However, greater participation is needed and therefore I request your engagement so we can move swiftly, with intention, to help ensure California’s essential food safety standards are known, implemented, and met. … I respectfully ask that you engage in the CALS project in a way that works for you and your operation.”

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