What to know about 'explosive diarrhoea' parasite outbreak in US

The United States is currently experiencing a significant outbreak of cyclosporiasis, a gastrointestinal illness caused by the microscopic parasite *Cyclospora cayetanensis*. As of July 9, 2026, the Centers for Disease Control and Prevention (CDC) reported 843 confirmed domestically acquired cases across 31 states, with an additional 1,500 suspected cases under investigation. Symptoms frequently include severe, watery, and often "explosive" diarrhea, along with nausea, fatigue, and abdominal cramps, which can persist for weeks. More than 80 individuals have been hospitalized, though no fatalities have been reported.

Michigan has been particularly hard-hit, reporting over 1,500 cases by July 10, marking it as the state's largest such outbreak in years. Neighboring Ohio also accounts for hundreds of cases, especially in counties bordering Michigan. Federal and state health agencies, including the CDC and FDA, are actively investigating multiple clusters to pinpoint the contaminated food or water source, which remains unidentified.

Cyclosporiasis is typically transmitted through the consumption of produce or water contaminated with human feces; direct person-to-person spread is considered unlikely. While the illness is generally not fatal, its debilitating symptoms can last for an extended period if untreated. Health officials emphasize the importance of thorough food safety practices, such as properly washing produce, to help prevent infection.