The number of cases of a parasitic illness that causes explosive diarrhea has risen to levels nearly four times the average annual total in the United States, federal data revealed Tuesday.

There have been 4,173 confirmed cases of cyclosporiasis across 41 states, the Centers for Disease Control and Prevention said. An additional 7,400 cases reported to the agency have yet to be confirmed.

Michigan state health officials have reported 6,571 cases, the most in the country. Cases there have been tied to contaminated lettuce. Cyclosporiasis spreads from exposure to produce contaminated with the cyclospora parasite.

In a typical year, there are only around 40-50 cases in Michigan and 1,000 infections across the U.S., according to the American Medical Association.

Infections are not life-threatening but they are particularly unpleasant. Cases often lead to vomiting, body aches, fever, fatigue and gastrointestinal distress that can leave patients dehydrated. “You’re barely able to make it to the toilet,” Dr. Alejandro Macías, an epidemiologist and physician at the University of Guanajuato in central Mexico, told The New York Times Wednesday.

Health Secretary Robert F. Kennedy Jr. said Tuesday that the outbreaks were “under control,” despite ballooning case numbers.

“We have done extensive forensics, epidemiological forensics and we have identified the source of the outbreak. We, and the companies that are involved, have implemented a recall,” he told reporters during a news conference.

A voluntary recall of iceberg lettuce from central Mexico was issued by California’s Taylor Farms last week based on an investigation from the Food and Drug Administration.

However, the source of outbreaks nationwide remains under investigation, the agency says.

That investigation led to some confusion earlier this week after the FDA said it had announced a “false positive test” – but insisted that reevaluating the sample did not alter data supporting an advisory that led to the Taylor Farms recall.

To date, no positive tests have been reported from any source.