(CNN) - An outbreak of E. coli linked to romaine lettuce from the Yuma, Arizona, growing region has spread to four additional states, the US Centers for Disease Control and Prevention announced Wednesday. Florida, Minnesota, North Dakota and Texas are the latest states to report illnesses, bringing the total to 29.
The CDC also reported 28 additional cases of illness, bringing the total to 149 since the outbreak began in March. Symptoms of the most recent illnesses reported began April 25. However, the CDC warned that due to a lag in reporting, any illness that occurred in the past two to three weeks may not have been counted in this update.
Last week, the CDC announced that one person had died; the death, in California, was the first known fatality. Previously, the CDC warned that the strain of E. coli identified, O157:H7, is particularly virulent and known to be associated with higher hospitalization and complication rates.
Sixty-four people have been hospitalized, the CDC said, and 17 of those have developed hemolytic uremic syndrome, a form of kidney failure that can be life-threatening, although most people recover in a few weeks.
Symptoms of E. coli begin on average three to four days after the bacteria are consumed. They include severe stomach cramps, diarrhea and vomiting. Most people recover in five to seven days with supportive treatment.
The CDC cautions against the use of antibiotics when dealing with this strain of E. coli because studies have connected antibiotic use with an increased risk for hemolytic uremic syndrome in both children and adults.
"Antibiotics are not recommended for patients with suspected E. coli O157 infections until diagnostic testing can be performed and E. coli O157 infection is ruled out," the CDC said.
The US Food and Drug Administration said it received confirmation from the Arizona Department of Agriculture that romaine lettuce is no longer being grown or shipped from the Yuma area. But there is a 21-day shelf life for romaine, the agency says, so there might still be lettuce in the supply chain.
However, the agency confirmed that no other types of lettuce or any other growing region for romaine are involved in the outbreak.
To explain the diverse geographical spread of this outbreak, the FDA said it is still investigating multiple points of origin and distribution. Last week, it identified Harrison Farms as the source of a single outbreak at a correctional facility in Nome, Alaska, that sickened eight inmates.
The growing season at that farm has ended, and the shelf life of the lettuce from there has passed. Therefore, it is not being sold or served anymore.
Because labels on romaine lettuce do not often list growing regions, it can be difficult for a consumer to tell whether the lettuce they are purchasing is part of the outbreak. The CDC warns consumers not to buy romaine unless they can verify the region of production.
"This advice includes whole heads and hearts of romaine, chopped romaine, baby romaine, organic romaine, and salads and salad mixes containing romaine lettuce," the CDC said. "If you do not know if the lettuce in a salad mix is romaine, do not eat it."
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