As the nation grapples with the COVID-19 public health emergency, the U.S. Food and Drug Administration is grateful for all that the food and agricultural sector is doing to provide safe and available food to consumers during this difficult time. As we work to get through the current challenge together, the FDA remains committed to protecting both the safety of workers and consumers from foodborne illness as we strive to ensure that America’s food supply remains resilient and among the safest in the world. As part of our ongoing efforts to combat foodborne illness, the FDA released the findings of an investigation into three outbreaks of E. coli O157:H7 illnesses that occurred in Fall 2019, all tied to romaine lettuce, that suggests the proximity of cattle to produce fields may have been a contributing factor.
The FDA worked with the Centers for Disease Control and Prevention (CDC) and state partners to investigate the contamination of romaine lettuce with several strains of E. coli O157:H7 that caused three outbreaks of foodborne illness beginning in September 2019 and which were declared over in January 2020. Some clusters (but not all) within each of these outbreaks were traced back to a common grower with multiple ranches/fields located in the Salinas, CA, growing region. Together, the outbreaks made 188 people ill.
During the course of on-farm investigations, one of the outbreak strains of E. coli O157:H7 was detected in a sample on public land less than two miles upslope from a produce farm with multiple fields that were identified during the traceback investigations. Other Shiga toxin-producing strains of E. coli (STEC) were found in closer proximity to where romaine lettuce crops were grown, including two samples from the border area of a farm immediately next to cattle grazing land in the hills above leafy greens fields and two samples from on-farm water drainage basins.
While these strains were not tied to the outbreaks, they do offer insight into the survival and movement of pathogens in this growing region. These findings, together with the findings from earlier leafy greens outbreaks, suggest that a potential contributing factor has been the proximity of cattle to the produce fields identified in traceback investigations. This is especially true when cattle are adjacent to and at higher elevations than produce fields.
In the report, “Investigation Report: Factors Potentially Contributing to the Contamination of Romaine Lettuce Implicated in the Three Outbreaks of E. coli O157:H7 During the Fall of 2019,” we’re calling on leafy greens growers to assess and mitigate risks associated with adjacent and nearby land uses, including grazing lands and animal operations. Of note, the number of cattle observed on nearby lands during the 2019 investigations was far lower than the volume of a large Concentrated Animal Feeding Operation, offering a useful reminder that high-density animal operations are not the only factor to consider. These key findings reinforce our concern about the possible impact of nearby and adjacent land use on the safety of leafy green crops and further underscore the importance of reviewing current operations and implementing appropriate risk mitigation strategies.