On Friday, the Centers for Disease Control and Prevention advised consumers not to eat and retailers not to sell the lettuce harvested in the California region, including "whole heads of romaine, hearts of romaine, and packages of precut lettuce and salad mixes which contain romaine, including baby romaine, spring mix, and Caesar salad."
Most romaine lettuce products are labeled with a harvest location showing where they were grown, according to the CDC. If it isn’t labeled with a growing region, don’t eat it, the CDC advises.
The Food and Drug Administration and the CDC are investigating a multistate outbreak of E. coli O157:H7 infections linked to the lettuce. Forty people have been infected from 16 states, according to the alert.
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A total of 28 hospitalizations have been reported. Five people developed hemolytic uremic syndrome, a type of kidney failure. No deaths have been reported.
“We are concerned about the potential for contaminated lettuce on store shelves and in people’s refrigerators," said Dr. Robert Tauxe, director of the CDC's Division of Foodborne, Waterborne and Environmental Diseases, in a statement sent to USA TODAY. "Heading into the Thanksgiving holiday, it is critically important to avoid buying or eating romaine lettuce from the Salinas growing area so you can protect yourself and your family.”
The CDC said no common grower, supplier, distributor, or brand of romaine lettuce has been identified.
The illnesses started Sept. 24, and cases have been reported through Nov. 10, the CDC said. The ages of those sickened range from 3 to 89 years, with a median age of 22.
Wisconsin has the most cases with 10, followed by Ohio with five and California with four. Idaho, Maryland and Pennsylvania each had three cases. Arizona and New Mexico each had two cases.
The following eight states had one reported case each as of Friday: Colorado, Illinois, Michigan, Minnesota, Montana, New Jersey, Virginia and Washington.
Among the reasons romaine lettuce is vulnerable is it has no protective rind and generally is eaten raw, food safety experts and academics said.
According to the FDA, "romaine lettuce that was harvested outside of the Salinas region has not been implicated in this outbreak investigation."
"Hydroponically- and greenhouse-grown romaine, which is voluntarily labeled as 'indoor grown,' from any region does not appear to be related to the current outbreak," the FDA said in a statement. "There is no recommendation for consumers or retailers to avoid using romaine harvested from these other sources."
Friday's warning comes almost exactly one year after a similar outbreak led to a blanket warning about tainted romaine before Thanksgiving 2018.
This outbreak is caused by the same strain of E. coli that caused outbreaks linked to leafy greens in 2017 and to romaine lettuce in 2018, the CDC said.
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California and Arizona are the top producers of leafy greens in the United States.
California produced about $1.8 billion in leafy greens in 2018 according to the 2018 State Agriculture Review; that was down from about $2.41 billion in 2017, likely due to the spring and fall 2018 E. coli outbreaks.
Bill Marler, a Seattle-based food safety attorney, said the FDA needs to require and the industry implement better environmental controls and more rigorous product testing.
“It is past time for the leafy green industry to take the safety of greens, especially romaine lettuce, seriously," Marler said. "There have been too many outbreaks leaving hundreds of consumers with life-long complications."
Contributing: Jessica Guynn, USA TODAY; Kate Cimini, The Salinas Californian
Follow USA TODAY reporter Kelly Tyko on Twitter: @KellyTyko
This article originally appeared on USA TODAY: Romaine lettuce safety alert: E. coli outbreak expanded, more ill