Parasitic illness cases linked to recalled iceberg lettuce have now been confirmed in 20 states, federal health officials said Thursday, expanding the scope of the largest outbreak of its kind in the U.S.

The Food and Drug Administration said government scientists have now identified cyclosporiasis cases in three additional states: Georgia, Tennessee and Texas. Other states impacted by the outbreak include Arkansas, Iowa, Illinois, Indiana, Kansas, Kentucky, Massachusetts, Maine, Michigan, Missouri, Nebraska, New Hampshire, North Carolina, Ohio, Oklahoma, Pennsylvania and West Virginia.

The tally of people sickened in the outbreak by the parasite cyclospora is now 11,458, the FDA said, up from about 10,900 reported last week. There have been two deaths linked to the outbreak, both reported in Michigan. The two residents had “significant underlying health conditions,” the state’s Department of Health and Human Services has said. 

The FDA, U.S. Centers for Disease Control and Prevention and state health officials have focused their investigation on lettuce grown at a farm in central Mexico operated by Taylor Farms, a major U.S. produce supplier. CBS News discovered that prior to the cyclosporiasis outbreak, the FDA last inspected its potential source, Taylor Farms de Mexico, seven years ago

The FDA said its staffers are continuing to inspect and test produce at the farm, in cooperation with officials from the Mexican government. The U.S. agency said it “remains confident that all recalled iceberg lettuce related to this specific cyclospora outbreak is off the market.”

Cyclospora is a microscopic parasite that commonly causes watery diarrhea “with frequent and sometimes explosive bowel movements,” according to the CDC. Outbreaks tend to occur most often in the late spring and summer.

The heat-loving parasite infects the bowels and spreads through feces. The illness, called cyclosporiasis, is less common than foodborne illnesses caused by other germs, including salmonella and E. coli. Many cyclosporiasis cases are never linked to a specific food or other source.

Earlier this week, the CDC reported that there have been about 17,180 confirmed cyclosporiasis cases in the U.S. this year. There have been 922 hospitalizations, according to the agency. Previously, the worst year in the U.S. for infections was 2019, when about 4,700 illnesses were reported nationally.