Fourteen more people have become ill from E. coli linked to romaine lettuce, the US Centers for Disease Control and Prevention said Friday. This brings the total number of illnesses from this outbreak to 98 people in 22 states, with Mississippi, Tennessee and Wisconsin as the newest states to report cases.
"We do expect more reports of illness since there is a two-week delay between when a person becomes ill and when they are confirmed to be part of an outbreak," said Matthew Wise, deputy branch chief for outbreak response at the CDC’s Division of Foodborne, Waterborne, and Environmental Diseases.
Forty-six of the ill individuals have been hospitalized, a higher rate than the 30% typically seen in E. coli outbreaks.
"CDC laboratory testing has confirmed that the strain of Shiga-toxin producing E. coli O157:H7 causing this outbreak produces a type of toxin that tends to cause more severe illness, which may explain why there is a high hospitalization rate," the agency said in an outbreak investigation update Friday.
Ten of the hospitalized patients have developed a type of kidney failure associated with E. coli called hemolytic uremic syndrome. They range in age from 18 to 87 years old, and three of them are children, according to the CDC.
The individuals who most recently became ill began experiencing symptoms April 20. Those symptoms include severe stomach cramps, diarrhea and vomiting. They begin, on average, three to four days after ingesting the bacteria. Most people recover in five to seven days. Those most at risk for E. coli illness include the very young, the very old and individuals with compromised immune systems.
"This is serious, and everyone should avoid romaine," Wise said, adding that the advice to consumers is for everyone — not limited to specific groups such as those most at risk for severe illness.
That advice: "Do not eat or buy romaine lettuce unless you can confirm it is not from the Yuma, Arizona, growing region. Restaurants and retailers should not serve or sell any romaine lettuce from the Yuma, Arizona, growing region."
The growing season in the Yuma region runs from November to March and then moves north to Salinas, California, for the summer. The move is underway, and some farms in Yuma have completed their season, but the FDA said it cannot confirm that no more lettuce is being shipped from the region based on the information it has from industry organizations.
The CDC and the Food and Drug Administration have yet to identify a brand, manufacturer, supplier or farm as the source of the E. coli contamination. However, they have identified Harrison Farms in Yuma as the grower of the whole heads of romaine that caused illness in eight inmates at a correctional facility in Nome, Alaska. The growing season at that farm has ended, but health investigators are planning to visit the farm in an effort to determine the how the lettuce became contaminated.
The CDC emphasized that although the other 90 cases of illness are linked to the eight in Alaska, those 90 are from chopped bagged lettuce, and that contamination source remains a mystery.
"At this point, we are looking at the whole spectrum" of the supply chain, said Stic Harris, director of the FDA’s Coordinated Outbreak Response and Evaluation Network. "As we go through the distribution of product, we are looking for places of convergence where the contamination may have happened. We are looking at each grower or shipper or supplier to see if there is a convergence."
There is no evidence that lettuce grown outside the Yuma region is part of this outbreak, according to Harris.
This is the largest outbreak of its kind since a deadly E. coli outbreak in 2006 that was linked to spinach. Unlike spinach, which is often cooked, romaine — and lettuce in general — is more common as a culprit in E. coli outbreaks because it’s eaten raw.
"There’s no kill step," Harris said, noting that he himself eats romaine several times a week.
© 2017 Cable News Network. Turner Broadcasting System, Inc. All Rights Reserved.