WASHINGTON (CNN) – The number of people hospitalized due to a multistate E. coli outbreak linked to chopped romaine lettuce continues to grow, the U.S. Centers for Disease Control and Prevention said.

About 53 people have been reported sickened in 16 states since March 13, the CDC stated. Of those who got ill, 31 have been hospitalized. Five of them developed a type of kidney failure associated with an E. coli illness, called hemolytic uremic syndrome, which can be life-threatening.

No deaths have been reported, the CDC said.

The higher numbers of E. coli cases have been reported in Pennsylvania, Idaho, New Jersey and Montana. The outbreak has also reached consumers in Alaska, Arizona, California, Connecticut, Illinois, Louisiana, Michigan, Missouri, New York, Ohio, Virginia and Washington.

Symptoms of E. coli typically begin two to eight days after consuming the bacteria, although most patients become ill three or four days after consumption. Those symptoms include severe stomach cramps, diarrhea and vomiting. Most people recover in five to seven days.

Those who are most at risk for illness include the very young, very old and individuals with compromised immune systems.

Health officials issued a warning for residents and restaurants last week about chopped romaine lettuce grown in the Yuma, Arizona area. The outbreak investigation is ongoing, and health officials have not yet identified a single brand, supplier, distributor or grower as the source of the contamination.

“Most people reported eating a salad at a restaurant, and romaine lettuce was the only common ingredient identified among the salads eaten,” the CDC said in a statement.

Pennsylvania-based Fresh Foods Manufacturing Co. issued a voluntary recall of ready-to-eat salads in clear plastic containers due to the potential for contamination. The 8,757 pounds of recalled salads were produced between April 9 and April 12 and sold in Indiana, Ohio, Pennsylvania and West Virginia. They have the establishment number P-40211 inside the USDA inspection mark on the package. Due to the four-day shelf life, the products should no longer be available in stores.

“Fresh Foods Manufacturing Co. received notification from their romaine lettuce supplier that the romaine lettuce used by the establishment in the products was being recalled due to E. coli O157:H7 concerns. There have been no confirmed reports of adverse reactions due to consumption of these products,” according to the U.S. Department of Agriculture, al;though the supplier was not identified and no other known recalls related to this outbreak have been issued thus far.

In the meantime, the CDC guidance for consumers remains unchanged. “The restaurants reported using bagged, chopped romaine lettuce to make salads. At this time, ill people are not reporting whole heads or hearts of romaine.” The agency recommends that people across the United States stay away from chopped romaine lettuce.

“Consumers anywhere in the United States who have store-bought chopped romaine lettuce at home, including salads and salad mixes, should not eat it and should throw it away, even if some of it was eaten and no one has gotten sick. If you do not know if the lettuce is romaine, do not eat it and throw it away,” the CDC said.

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