The U.S. Food and Drug Administration's outbreak investigations page lists an active Cyclospora investigation — reference number 1375 — with cases increasing since the last update, and the source of contamination has not yet been identified. This is not the kind of headline that generates mass alarm, but it should generate immediate consumer awareness, because Cyclospora is a parasite that causes weeks of profuse watery diarrhea with fatigue and weight loss, because summer is its peak transmission season, and because the foods most frequently linked to Cyclospora outbreaks in the United States — bagged salads, fresh cilantro, basil, and leafy greens — are among the most commonly consumed summer foods in America.
Cyclospora cayetanensis is a microscopic parasite that infects the small intestine, causing a syndrome of profuse, often watery diarrhea that begins approximately one week after exposure and can last for weeks to months in untreated cases. Unlike most foodborne pathogens whose symptoms resolve in a few days, Cyclospora produces a characteristically prolonged illness — diarrhea cycles between profuse and less severe, with periods of temporary improvement that trick patients into thinking they are recovering before the diarrhea returns. Fatigue, nausea, appetite loss, bloating, and significant weight loss are common. In otherwise healthy adults, Cyclospora is rarely fatal — but it is profoundly debilitating, and it is responsible for a surprising number of hospitalizations each year.
In 2025, 1,180 cases of cyclosporiasis acquired in the United States were reported to the CDC from 38 states, with 105 people hospitalized. The peak illness onset period was concentrated in May through August — exactly the period now underway. These figures represent only confirmed, reported cases; the true annual burden is substantially higher, as most people with mild infections do not seek medical care or receive testing.
What Foods Most Commonly Carry Cyclospora
The parasite's transmission in the United States is almost entirely foodborne, and the implicated foods share a common characteristic: they are fresh, uncooked, or minimally processed plant products that may be contaminated with infected human feces during agricultural production or handling. Past CDC investigations have linked Cyclospora outbreaks to:
Bagged Caesar salad kits — linked to a Florida-centered outbreak in 2022 that involved more than 161 cases linked to romaine-containing kits from a specific grocery store chain.
Fresh cilantro — linked to multiple outbreaks in the Mid-Atlantic United States, particularly from products sourced from farms in Puebla, Mexico.
Fresh basil — linked to a multi-state outbreak in 2019 that sickened 641 people across 33 states.
Leafy greens, including arugula, mixed greens, and baby spinach — linked to multiple outbreaks from 2018 through 2023.
The current active investigation (ref #1375) has not yet identified a specific implicated food. The FDA's outbreak investigations page states that the case count has increased from 7 to 8 since the last update, with investigations ongoing by FDA, CDC, and state public health partners.
Treatment, Prevention, and What to Do Right Now
Cyclosporiasis is treated with trimethoprim-sulfamethoxazole (TMP-SMX, Bactrim) — the combination antibiotic is effective and is the only validated treatment option. Importantly, the illness does not respond to most other antibiotics or antiparasitic medications, which means an incorrect empirical treatment will not provide benefit and will delay effective care. Any patient with prolonged watery diarrhea lasting more than a week — especially after consuming fresh produce — should be specifically tested for Cyclospora through stool microscopy with modified acid-fast staining or PCR testing. Standard stool ova-and-parasite examinations may miss Cyclospora unless the laboratory is specifically requested to look for it.
For consumers, the prevention strategy centers on food handling: washing produce thoroughly under running water before consumption, considering the provenance of high-risk items (cilantro, basil, mixed salad greens), and promptly seeking medical care with appropriate disclosure of food history if watery diarrhea lasting more than 5 to 7 days develops in summer months.
Frequently Asked Questions
Q: What is Cyclospora and what are the symptoms?
A: Cyclospora cayetanensis is a microscopic parasite that causes cyclosporiasis — weeks to months of profuse, cycling watery diarrhea with fatigue, nausea, appetite loss, weight loss, and bloating. Symptoms typically begin about one week after exposure.
Q: Is there an active Cyclospora outbreak right now?
A: Yes. The FDA is actively investigating a Cyclospora outbreak (ref #1375) with cases increasing and the source not yet identified as of the most recent update.
Q: What foods are most commonly linked to Cyclospora?
A: Fresh cilantro, basil, bagged salad kits (especially Caesar salad), leafy greens, and other minimally processed fresh produce. Past outbreaks have involved items from Mexico, Guatemala, and domestic farms.
Q: How is cyclosporiasis treated?
A: With trimethoprim-sulfamethoxazole (TMP-SMX, Bactrim). This is the only validated effective treatment — standard antiparasitic drugs and most antibiotics do not work. Testing should specifically request Cyclospora detection, as it may be missed on standard stool exams.
Q: Who is most likely to develop severe illness from Cyclospora?
A: Immunocompromised individuals — those with HIV, transplant recipients, or those on immunosuppressive therapy — are at risk for prolonged, more severe illness. In healthy adults, the illness is rarely fatal but is highly debilitating.
