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Cows in the Salinas Valley area of California have been blamed for three E. coli outbreaks in late 2019 that sickened 188 people in at least 27 states, according to a U.S. Food and Drug Administration report released in May. 

The FDA’s investigation into the fall 2019 E. coli outbreak of romaine lettuce from a single grower found that one of the main contributing factors was contaminated fecal matter from nearby cattle grazes.

The actual route of transmission from cattle to produce is unknown but may have been caused by run-off down hills and into rivers contaminating water sources, or direct transmission from wind, animals or farming activities such as vehicles, harvest crews or harvest equipment. 

Three different strains of E. coli O157:H7 were found. Outbreak A with 167 illnesses, outbreak B with 11 and C with 10 illnesses. E. coli O157:H7 is a form of the bacteria known as Shiga toxin-producing E. Coli (STEC), which can cause severe illness and, in some people, a potentially fatal form of kidney disease.  

There were no deaths reported with these outbreaks, but 92 people were hospitalized, according to the FDA.

States with outbreaks include: Arizona, California, Colorado, Delaware, Florida, Illinois, Indiana, Iowa, Maryland, Michigan, Minnesota, Montana, Nebraska, New Jersey, North Carolina, New Mexico, New York, Ohio, Oregon, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Virginia, Washington and Wisconsin.


The FDA, along with state and federal partners, investigated these three outbreak strains to identify any factors that may have led to the contamination of romaine lettuce with E. coli O157:H7.

Outbreak A strain of E. coli O157:H7 was found in contaminated romaine lettuce from the Salinas Valley in California. Outbreak A was responsible for the majority of illnesses from  E. coli O157:H7. Outbreak A came from a fecal-soil composite sample taken from a cattle grate on public land less than two miles from a produce farm that had multiple fields connected to the outbreaks. 

To prevent future E. coli outbreaks the FDA released a report called Leafy Greens STEC Action Plan. This report includes recommendations to make lettuce growing safer. 

Some of these recommendations include increasing the distance between cattle grazes and produce fields; adding physical barriers to produce fields such as walls and diversion ditches; enhancing inspection, auditing, and certification programs; and engaging buyers to strengthen their food safety specifications. 

The California Leafy Greens Marketing Agreement in a statement said, “the members of LGMA are committed to making real changes to improve the safety of our product.”