Nationwide "Explosive Diarrhea" Outbreak Tops 2,000 Cases

What Is Cyclosporiasis?

Cyclosporiasis is an intestinal infection caused by the Cyclospora parasite. When individuals consume food or water contaminated with feces containing the parasite, it infects the small intestine. [2] The most prominent and uncomfortable symptom is frequent, watery, and sometimes explosive bowel movements. [2]

The six hallmark symptoms of a Cyclospora infection. Source: CDC.

The incubation period — the time between ingesting the parasite and feeling sick — is typically about one week, though it can range from two to 14 days. [2] [4] Because the parasite requires at least one to two weeks outside the body to become infectious, direct person-to-person transmission is highly unlikely. [2] If left untreated, symptoms can persist for over a month and may seemingly resolve only to return later. [2]

The July 2026 Outbreak: A Massive Surge

The summer months traditionally see an increase in Cyclospora cases, creating a "cyclosporiasis season" that the CDC tracks from May 1 to August 31. [2] [5] However, the summer of 2026 has seen an alarming spike that has caught public health officials off guard.

As of July 10, 2026, the outbreak has affected individuals across at least 18 states. [3] Michigan has been hit particularly hard, reporting more than 1,500 cases — a massive jump from the state's annual average of just 50 cases, making it the largest outbreak in the state's history. [1] [4]

Confirmed cyclosporiasis cases by state, updated July 10, 2026.

The CDC noted that the true number of infections is likely much higher, as many people recover without seeking medical testing or care. [2] Furthermore, tracking the outbreak nationally has been complicated because the CDC made state reporting of Cyclospora optional in 2025. [1] [4]

The Challenge of Finding the Source

Despite the rising numbers, local and federal authorities have not yet identified a single, multistate source for the outbreak. [1] [2]

Investigating foodborne illnesses is notoriously difficult, particularly with Cyclospora. The long incubation period makes it hard for patients to recall exactly what they ate weeks prior. [6]

Furthermore, the parasite is historically linked to fresh produce — such as cilantro, parsley, basil, raspberries, and bagged salad mixes — which are often used as minor ingredients in meals and easily forgotten. [1] [6] By the time a common ingredient is identified among patients, the short shelf life of fresh produce means the contaminated product has usually already been discarded from the food supply. [6]

The Michigan Department of Health and Human Services recently issued guidance urging restaurants and commercial kitchens to implement enhanced washing procedures for lettuce, herbs, green onions, raspberries, and snow peas. [4]

Prevention and Treatment

While investigators continue to search for the source, health officials emphasize that prevention is the best defense.

Five key prevention steps recommended by the CDC and USA Today, July 2026.

For those who do fall ill, a healthcare provider can diagnose cyclosporiasis through specific stool tests — it is important to note that standard stool tests do not detect Cyclospora, so patients must specifically request testing for it. [2] The infection is typically treated with a combination antibiotic, trimethoprim-sulfamethoxazole (commonly known as Bactrim or Septra). [2] Resting and staying well-hydrated are also crucial for recovery. [2]

Conclusion

The 2026 cyclosporiasis outbreak is a stark reminder of the vulnerability of the food supply chain and the importance of food safety practices. As the CDC and FDA continue their investigation, the public is urged to remain vigilant, wash produce thoroughly, and seek medical attention if severe gastrointestinal symptoms develop. Cases are expected to continue rising through August as the summer season progresses.