On Tuesday, the Centers for Disease Control and Prevention said thousands more suspected cases remain under investigation as federal and state officials probe a multistate outbreak linked to recalled iceberg lettuce.

Cyclospora Cases Rise

The CDC said that it has confirmed 4,173 domestically acquired cases of cyclosporiasis since May 1, with 308 hospitalizations reported across 41 states. No deaths have been recorded, Reuters reported.

The agency also said it is aware of more than 7,400 additional reported cases that have not yet been laboratory confirmed and require further investigation, with many of the reports coming from Michigan and Ohio.

The CDC said the number of confirmed cases is likely to increase due to reporting delays between the onset of illness and notification to federal health officials.

Federal investigators, alongside the U.S. Food and Drug Administration and state health officials, are investigating a five-state outbreak linked to iceberg lettuce.

Lettuce Recall Investigation

On July 17, Taylor Farms recalled iceberg lettuce sourced from central Mexico that had been sold in retail stores, served in restaurants and distributed to food service customers.

According to the CDC, cyclosporiasis is an intestinal illness caused by the Cyclospora parasite, which spreads through contaminated food or water.

Symptoms include diarrhea, stomach cramps, nausea and fatigue.

The confirmed domestically acquired cases involve patients ages 2 to 95, with a median age of 44. The median illness onset date was June 26.

Separately, the CDC reported 767 travel-associated cases, including 33 hospitalizations, tied to contaminated food or water consumed outside the United States.

Kennedy, Blumenthal on Cyclospora Probe

Sen. Richard Blumenthal (D-Conn.) criticized the CDC’s handling of the Cyclospora outbreak, calling for more details on its source and spread while blaming staffing cuts and reduced reporting requirements for a delayed response.

Health Secretary Robert F. Kennedy Jr. said on Tuesday that the Cyclospora outbreak was "under control" and denied that staffing cuts weakened surveillance efforts, CNBC reported.

FDA Updates Cyclospora Lettuce Investigation

The FDA said a Taylor Farms lettuce sample that initially tested positive for Cyclospora was later found to be a false positive. However, investigators continued to trace the outbreak to shredded iceberg lettuce supplied by Taylor Farms to Taco Bell.

The company’s recall across 27 states remained active, while Taco Bell removed the lettuce from affected locations.

Last week, the investigation involved lettuce processed at Taylor Farms’ Guanajuato, Mexico facility and linked to Cyclospora cases in five states, resulting in 94 hospitalizations and no reported deaths.

Sysco Corporation (SYY) also paused distribution of the recalled lettuce. Taylor Farms said its branded salad kits were not connected to the outbreak.