Cyclosporiasis outbreak spreads across 31 US states with nearly 3,000 cases reported

A gastrointestinal parasite outbreak has sickened nearly 3,000 people across 31 US states, with Michigan experiencing the most severe cases. Health authorities have confirmed 843 infections and are investigating more than 1,500 additional suspected cases, though the contaminated food source remains unidentified. No deaths have been reported, though 86 people have required hospitalization.

Outbreak Severity and Geographic Spread

Michigan has borne the brunt of the cyclosporiasis outbreak, with the state reporting 1,562 confirmed cases as of recent data releases. This represents an extraordinary spike compared to the state's typical annual caseload of 40 to 50 infections. New York has recorded nearly 300 cases, while Ohio reported 177 cases and Illinois confirmed 141 infections. Other affected states include Colorado, North Carolina, Texas, and Wisconsin, among others.

Dr. Natasha Bagdasarian, chief medical executive of Michigan, characterized the rapid rise as "highly unusual" for the season. Laboratory technicians across the state have begun genomic sequencing of the parasite isolates to determine whether different state outbreaks share a common source or stem from separate contamination events.

The Parasite and Infection Timeline

Cyclosporiasis is caused by a microscopic parasite that contaminates food and water. Infected individuals typically experience frequent, watery, and explosive bowel movements, with symptoms appearing approximately one week after exposure. If left untreated, the illness can persist from several days to more than a month, and symptoms may recur even after initial improvement. Most cases are not life-threatening, though the condition proves considerably more severe than average foodborne illnesses.

The challenge facing investigators stems from the infection's lengthy incubation period. People consuming contaminated food more than a week ago are only now developing symptoms, by which time the source has often been combined with other ingredients or discarded entirely. Cilantro in salsa and bagged lettuce in salads represent common vectors for parasite transmission, as cyclospora organisms cling stubbornly to produce and resist standard rinsing.

Investigation and Food Safety Response

The Centers for Disease Control and Prevention has indicated uncertainty about whether outbreaks across multiple states represent a single source or separate contamination events. Fresh produce has historically been implicated in cyclosporiasis outbreaks, though identifying the specific item proves difficult. The FDA reported active engagement with state partners but has issued no product recalls to date. Dianna Blau, acting chief of the CDC's Parasitic Disease Branch, noted that in an average year, only a small proportion of cyclosporiasis cases are ultimately traced to a specific food item.