The U.S. Food and Drug Administration 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.

Between August and December 2020, the FDA and multiple state and federal partners were involved in an investigation into an outbreak of E. coli O157: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.

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.  

Reoccurring outbreak strain

The FDA analyzed outbreaks that 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.

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.

An updated version of the Leafy Green STEC Action Plan has been released, which reaffirms the FDA's 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 the FDA'scommitment to completing certain actions that were difficult to accomplish in 2020 due to challenges presented by the COVID-19 pandemic.

For more information visit E. coli and Foodborne Illness.