The U.S. Food and Drug Administration (FDA) has declared that three E. coli outbreaks linked to romaine lettuce grown in Salinas, California are now over.

The FDA previously was able to identify a common grower between each of these outbreaks in Salinas based on available supply chain information.

It is lifting the consumer advisory to avoid romaine lettuce from the area as the growing season for this region is over and there is no longer a need for consumers to avoid it. 

The FDA and CDC have been tracking two multi-state romaine lettuce outbreaks. Today, federal health officials are declaring both multi-state romaine lettuce outbreaks over.

One of the outbreaks sickened 167 people in 27 states. The other outbreak, linked to Fresh Express salad kits, sickened 10 people in five states.

There was also a third outbreak in Washington State that sickened 11 people. This outbreak has also been declared over.

The last reported illness onset date for all the outbreaks was Dec. 21.

"Based on this information, it appears that our Nov. 22 advisory to not eat romaine from Salinas played an important role in preventing illnesses and containing this outbreak because it prompted the removal of romaine lettuce from Salinas from the marketplace and warned consumers to throw away romaine from that growing region," the FDA said.

Common grower, multiple fields investigated

The FDA traceback investigation for these outbreaks required investigators to go through hundreds of supply chain records to find a commonality to a single grower with multiple fields.

"We were able to narrow this down further to at least 10 fields in the lower Salinas Valley," it said.

Investigators visited several of these fields and took a variety of samples from water, soil and compost. So far, sample results have come back negative for all of the three outbreak strains of E. coli O157:H7.

However, they did find a strain that is unrelated to any illnesses in a soil sample taken near a run-off point in a buffer zone between a field where product was harvested and where cattle are known to occasionally graze.

"This could be an important clue that will be further examined as our investigation continues. However, this clue does not explain the illnesses seen in these outbreaks," it said.

"Our investigation is ongoing, and we are doing everything possible to find the source or sources of contamination. The investigation into how this contamination occurred is important, so romaine growers can implement measures that will prevent future contamination and illnesses."

The FDA said it is also planning to conduct an "additional, in-depth, root-cause investigation".

"The investigation will further characterize how contamination might have occurred and will inform what preventive controls are needed to prevent future outbreaks," it said.

"Once complete, we plan to issue a prompt report and share lessons learned, so that growers can implement best practices to protect consumers from contaminated produce."