The harvest season for romaine lettuce linked to a national E. coli outbreak ended April 16. As romaine only has a 21-day shelf life, it is unlikely the contaminated lettuce is still on grocery store shelves or in consumers' fridges, according to a May 16 CDC update.
The CDC traced the contaminated romaine to Yuma, Ariz., where most of the country's lettuce is grown during the winter. However, much of the U.S.'s lettuce supply is now being harvested in California, according to The Washington Post.
"It takes two to three weeks between when a person becomes ill with E. coli and when the illness is reported to CDC," the agency said. "The most recent illnesses reported to CDC started when romaine lettuce from the Yuma growing region was probably still available in stores, restaurants and in peoples' homes."
The outbreak has sickened 172 people across 32 states as of May 15. Of those sickened, 75 required hospitalization, 20 experienced kidney failure and one died.
The FDA is still investigating the circumstances behind the romaine lettuce's contamination. The agency "ruled out that the contamination was caused by just one farm, suggesting it was a complex problem and will take further time to investigate," FDA Commissioner Scott Gottlieb, MD, tweeted May 16.