U.S. health officials have declared the outbreak at the heart of the largest known surge of cyclosporiasis in the nation is over as new cases in Ohio fell dramatically the past week.
Ohio's 15 new cases this week are a 78.5% decrease from the 70 new cases last week amid a nationwide outbreak.
As of Sept. 17, the Ohio Department of Health is reporting 6,427 cases of cyclosporiasis, a gastrointestinal illness caused by a parasite known as cyclospora cayatenensis, in 85 counties so far in 2026. That's up slightly from 6,412 cases in 85 counties as of Sept. 10. All but nine of the cases in the state this year occurred since June 20.
But the rate of increase has been slowing down over the past several weeks. ODH reported:
- 1,437 new cases from July 24 to 30
- 936 from July 31 to Aug. 6 (down 34% from the previous week)
- 503 from Aug. 7 to 13 (down 46%)
- 422 from Aug. 14 to 20 (down 16%)
- 189 from Aug. 21 to 27 (down 55%)
- 279 from Aug. 28 to Sept. 3 (up 47%)
- 70 from Sept. 4 to 10 (down 75%)
- 15 from Sept. 11 to 17 (down 78.5%)
Ohio and Michigan were leading
the nation in cyclosporiasis cases, with Michigan's health department stating on Sept. 3, its most recent update, that it had 14,718 cases, including the first two deaths identified in the nationwide outbreak.
Nationwide, the outbreak linked to iceberg lettuce that accounts for more than 10,000 cases in 17 states has been declared "over" by the U.S. Centers for Disease Control and Prevention. The agency, which lags significantly behind states in reporting infections, has pinpointed 19,883 laboratory-confirmed cases across 49 states plus Washington D.C., between May 1 and its latest update Sept. 15. Only Delaware is not reporting any cases.
The CDC stated it would stop updating its cyclosporiasis suveillance data as of Sept. 15 because the number of recent infections has significantly declined. Cyclospora season in the United States technically ended Aug. 31.
Cyclospora parasite outbreak linked to lettuce that accounts for more than 10,000 cases declared 'over' by CDC
The outbreak at the center of the nation's largest known surge of the explosive diarrhea illness cyclosporiasis is over, officials say.
The Centers for Disease Control and Prevention declared the outbreak, linked directly to lettuce, as ended on Sept. 11, with a tally of 12,883 lab-confirmed cases across 21 states since May 1.
The CDC is still investigating several case clusters of the parasitic illness nationwide, but has only identified the source of one – iceberg lettuce grown by produce giant Taylor Farms in Mexico. At least five other outbreaks are still under investigation, according to the Food and Drug Administration's foodborne illness investigations page.
See map of states with cyclosporiasis cases
New Mexico was the latest state added to the CDC's list of those with confirmed cases. Only Delaware does not have federally confirmed cases. Michigan and Ohio remain the two states hit the hardest.
The CDC reports only lab-confirmed cases that occurred on or after May 1 in people who did not travel internationally within 14 days of illness onset. Its numbers often lag behind those cited by state health officials because of tracking, verification and reporting processes. There's typically a six-week reporting lag between an illness and the case being reported to the CDC.
Which Ohio counties are hit by cyclosporiasis?
These are the counties reporting 2026 cyclosporiasis cases in Ohio as of Sept. 10, and the number of new cases, according to ODH:
- Adams: 1
- Allen: 10
- Ashland: 22
- Ashtabula: 92
- Athens: 4
- Auglaize: 5
- Belmont: 3
- Brown: 1
- Butler: 31
- Carroll: 19
- Champaign: 2
- Clark: 13
- Clermont: 9
- Columbiana: 31 (one new case)
- Coshocton: 4
- Crawford: 41
- Cuyahoga: 860 (three new cases)
- Darke: 10
- Defiance: 182 (two new cases)
- Delaware: 20
- Erie: 161
- Fairfield: 33
- Fayette: 2
- Franklin: 170
- Fulton: 188
- Gallia: 14
- Geauga: 44
- Greene: 25
- Guernsey: 2
- Hamilton: 62
- Hancock: 16
- Hardin: 11
- Harrison: 2
- Henry: 106
- Highland: 6
- Holmes: 3
- Huron: 139 (two new cases)
- Jackson: 13
- Jefferson: 15
- Knox: 6
- Lake: 120 (one new case)
- Lawrence: 17
- Licking: 41
- Logan: 4
- Lorain: 378 (one new case)
- Lucas: 1,109 (two new cases)
- Madison: 3
- Mahoning: 63
- Marion: 9
- Medina: 167
- Meigs: 5
- Mercer: 20
- Miami: 9
- Monroe: 1
- Montgomery: 51
- Morgan: 3
- Morrow: 24
- Muskingum: 7
- Noble: 1
- Ottawa: 59
- Paulding: 88
- Pickaway: 8
- Pike: 4
- Portage: 216
- Preble: 7
- Putnam: 9
- Richland: 42
- Ross: 31
- Sandusky: 333
- Scioto: 14
- Seneca: 37
- Shelby: 3
- Stark: 150
- Summit: 218
- Trumbull: 46
- Tuscarawas: 26
- Union: 15
- Van Wert: 10
- Vinton: 3
- Warren: 16
- Washington: 5
- Wayne: 43 (one new case)
- Williams: 33
- Wood: 544 (two new cases)
- Wyandot: 54
- Unknown county: 3
How do I know if I have cyclosporiasis? Symptoms, testing
Symptoms of cyclosporiasis may include:
- Explosive, watery diarrhea (most common)
- Loss of appetite
- Weight loss
- Cramping
- Bloating
- Increased gas
- Nausea
- Fatigue
Less common symptoms may include:
- Vomiting
- Body aches
- Headache
- Low-grade fever
- Other flu-like symptoms
Symptoms begin about a week after being infected and can last anywhere from a few days to a month or longer without treatment. Some symptoms, such as diarrhea, may go away and then return.
The illness is diagnosed by testing stool samples, according to the CDC.
Cyclosporiasis prevention. How to protect yourself
The CDC says the best way to prevent cyclosporiasis is to avoid food or water that may be contaminated with feces.
And to help do that, the agency recommends safe food-handling practices when dealing with produce, including:
- Wash hands with soap and water before and after handling or preparing raw fruits and vegetables.
- Wash all fruits and vegetables thoroughly under running water before eating, cutting or cooking.
- Scrub firm fruits and vegetables, such as melons and cucumbers, with a clean produce brush.
- Cut away any damaged or bruised areas on fruits and vegetables before preparing and eating.
- Refrigerate cut, peeled or cooked fruits and vegetables as soon as possible (within two hours).
This article originally appeared on USA TODAY: CDC declares cyclosporiasis outbreak over, new Ohio cases drop significantly
