The Seneca County General Health District says it is continuing to monitor cases of cyclosporiasis in the county, with 5 lab-confirmed cases reported to the health district as of Monday, July 13.

The source of the outbreak is unknown and under investigation, the health district said in a news release.

Cyclosporiasis is an intestinal illness caused by a microscopic parasite. People become infected by consuming food or water contaminated with the parasite. Symptoms include intense, watery diarrhea, loss of appetite, weight loss, cramping, bloating, nausea and fatigue, and typically develop within two to 14 days after exposure. The health district said person-to-person spread is extremely unlikely.

The illness can cause prolonged illness in older adults, pregnant women, young children, and people with weakened immune systems or underlying health conditions, according to the health district. Anyone experiencing symptoms should contact a healthcare provider; early diagnosis and treatment can shorten the illness and prevent complications.

Part of a broader Ohio and Midwest increase

The Seneca County cases come as cyclosporiasis case counts climb across Ohio and neighboring states.

The Ohio Department of Health reported 177 cases statewide in 2026 as of July 2, with 171 of those occurring in June, mostly after June 20. Twenty-eight Ohioans had been hospitalized. No deaths have been reported in Ohio.

ODH Director Bruce Vanderhoff said the illness is not typically life-threatening but called it “a serious illness that can cause dehydration” and said it can require people to seek emergency medical care.

The state’s most recent public county-level breakdown, reflecting data as of July 2, listed 2 cases in Seneca County. The health district’s figure of 5 lab-confirmed cases reflects a later date and is drawn from cases reported directly to the district; the two counts are not a direct comparison.

That same state breakdown shows heavier concentrations elsewhere in northwest Ohio: 30 cases in Lucas County, 20 in Wood County, 10 in Wyandot County, 7 in Crawford County, 5 in Fulton County and 2 in Sandusky County.

ODH said it is working with local health departments and with state and federal partners on interviews and traceback investigations to identify any common exposure. As of that release, no common source had been identified. The illness is generally transmitted by eating contaminated produce, and ODH said it can be treated with antibiotics, along with rest and fluids.

How to reduce your risk

The health district listed several preventative steps residents can take while the investigation continues:

  • Wash your hands with soap and water before preparing or eating food.

  • Carefully wash all produce.

  • When able, cook produce to at least 160 degrees Fahrenheit.

  • If you are experiencing gastrointestinal symptoms such as diarrhea, do not swim or visit splashpads. The health district noted that one person with diarrhea can spread germs to everyone else in a pool.

The Seneca County General Health District can be reached at its Tiffin office, 92 E. Perry St., at 419-447-3691, or its Fostoria office, 801 Kirk St., at 419-435-4401.

More information about the illness is available from the Centers for Disease Control and Prevention.