This is a particularly bad strain of E. coli , and more than half of the people who have gotten sick have ended up in the hospital.

Far from slowing down, the outbreak linked to romaine lettuce is widening, the US Centers for Disease and Control and Prevention announced Friday. Rena-Marie / Getty Images

So far, a total of 98 people in 22 states have gotten sick after eating romaine lettuce. That's an additional 14 patients and three new states — Mississippi, Tennessee, and Wisconsin — since last week. While chopped romaine sold either alone or in mixed salads was originally thought to be the culprit, last week the warning was expanded to include all types of romaine — chopped, whole heads and hearts of romaine, organic and baby romaine, and any salads or mixed salads that contain romaine. The warning was updated after a group of inmates at a correctional facility in Alaska got sick from eating food containing whole romaine lettuce. "People should still not eat any type of romaine lettuce unless they know for sure it does not come from the Yuma-growing region," said Matthew Wise, deputy branch chief for outbreak response at Centers for Disease Control and Prevention, at a press conference. Here is a complete list of states with cases: Alaska, Arizona, California, Colorado, Connecticut, Georgia, Idaho, Illinois, Louisiana, Michigan, Mississippi, Missouri, Montana, New Jersey, New York, Ohio, Pennsylvania, South Dakota, Tennessee, Virginia, Washington, and Wisconsin.

Throw out any type of romaine lettuce unless you can confirm it was not grown in Yuma, Arizona. Gomezdavid / Getty Images

Yuma, Arizona, is the general location of the outbreak's source. Experts have not located the farm or farms responsible for the majority of cases, and don't know if the contamination occurred during the harvesting, packaging, or distribution of the lettuce. The CDC did identify one farm associated with the outbreak but said it's not the source for most cases. That farm, Harrison Farms of Yuma, Arizona, is thought to be responsible for the Alaska cases linked to whole romaine, but not the rest of the cases, which have been traced to chopped romaine. "We have not determined where in the supply chain the contamination occurred," Wise said. The US Food and Drug Administration is investigating at least two dozen farms as possible sources.

Janice Haney Carr / CDC / Via phil.cdc.gov