A microscopic intestinal parasite has sickened 145 people across 17 states since May 1, 2026, and federal investigators have not yet identified the food source.
According to CDC surveillance data, 145 domestically acquired Cyclospora cases were confirmed as of mid-June 2026, with a median illness onset of May 19. Three people have been hospitalized. No deaths have been reported. The FDA's active outbreak investigations table lists the investigation as ongoing.
Summer is peak season for Cyclospora cayetanensis in the United States. Previous outbreaks have been linked to bagged salad kits, fresh cilantro, basil, and leafy greens — but traceback in this investigation has not yet identified a specific food product or supplier.
Why This Matters
Cyclospora is frequently missed by both patients and physicians because it is not part of a standard stool culture. Most clinical labs do not routinely test for Cyclospora unless it is specifically requested. This means many cases — perhaps the majority — are never diagnosed, giving patients and their doctors the impression they have a prolonged viral illness when a treatable parasitic infection is actually the cause.
The parasite also has an unusually long incubation period — about one week after exposure — and produces illness that can last weeks to months if untreated. The combination of these factors makes Cyclospora substantially different from typical food poisoning, and understanding those differences is essential for people who develop summer diarrhea after consuming fresh produce.
What We Know So Far
The Cyclospora outbreak was identified through routine CDC and FDA foodborne illness surveillance. Cases are spread across 17 states with no obvious geographic concentration — a pattern consistent with contaminated commercially distributed produce or herbs with national distribution.
Prior Cyclospora outbreaks in the United States have followed a consistent seasonal pattern, peaking from May through August and declining in September. The outbreaks have repeatedly been linked to fresh produce with Mexican origins — particularly cilantro, basil, and leafy salad greens. But the investigation in 2026 has not yet confirmed a specific food source.
The current case count of 145 is almost certainly an underestimate. The CDC estimates that for every confirmed Cyclospora case, many more go undiagnosed due to the absence of routine testing. A Food Safety Magazine analysisnoted that none of the major recent Cyclospora outbreaks was able to definitively identify the mode or method of contamination — consistent with the ongoing difficulty in tracing the infection to a specific product.
What Makes Cyclospora Different
Most food poisoning symptoms begin within hours of exposure. Cyclospora is different in four important ways:
- Incubation period. Cyclospora takes about one week — sometimes up to two — to cause symptoms after exposure. Patients who ate a contaminated salad last Tuesday may not feel ill until next week.
- Duration. Untreated Cyclospora illness can last four to six weeks, or even longer in immunocompromised individuals. The pattern of relapsing-remitting diarrhea — where symptoms temporarily improve and then return — is a distinguishing feature.
- Testing. Standard stool cultures do NOT detect Cyclospora. A physician must specifically order modified acid-fast staining or PCR testing for the parasite. Patients who receive only a standard stool culture will get a negative result and may be told nothing is wrong.
- Treatment. Cyclospora is treated with trimethoprim-sulfamethoxazole (TMP-SMX, or Bactrim). Over-the-counter antidiarrheal medications address symptoms but do not eliminate the infection. No other antibiotic regimen has been shown to be effective.
Where the Risk Is Highest
Fresh leafy greens, herbs — particularly cilantro, basil, and flat-leaf parsley — and bagged salad kits with international supply chain ingredients remain the food categories most closely associated with Cyclospora outbreaks based on historical patterns. Until the current outbreak's food source is identified, there is no specific product to avoid. Standard produce hygiene should be followed.
Travelers returning from countries where Cyclospora is endemic — including Guatemala, Peru, Nepal, and other tropical and subtropical countries — may also bring the infection home. Any person with prolonged diarrhea following international travel should ask specifically about Cyclospora testing.
Symptoms and Warning Signs to Watch For
Cyclospora cayetanensis causes cyclosporiasis, a gastrointestinal illness with the following profile:
- Watery diarrhea, often explosive and frequent
- Loss of appetite and significant weight loss
- Fatigue, sometimes severe
- Bloating, gas, and stomach cramping
- Low-grade fever and body aches
- Nausea and vomiting
Symptoms often improve and then relapse. If you develop prolonged diarrhea lasting more than five days — particularly with fatigue and loss of appetite after eating fresh produce or herbs — contact your physician and specifically ask them to test for Cyclospora. Do not rely on a standard stool culture.
What You Can Do Now
- Wash all fresh produce — including bagged salad greens — under cold running water before eating. Note that washing does not eliminate Cyclospora spores completely, but it reduces the contamination load.
- If you develop prolonged watery diarrhea lasting more than five days in summer, contact a clinician and specifically mention Cyclospora as a diagnostic possibility. Ask for modified acid-fast staining or PCR testing.
- If diagnosed with Cyclospora, ask your doctor about treatment with TMP-SMX. Untreated illness can last weeks to months.
- Monitor the FDA's outbreak investigations page for any specific food recalls or alerts that emerge from this investigation.
- If you are immunocompromised, discuss fresh produce consumption with your health care provider during active summer Cyclospora seasons.
Cost and Access: What Patients Should Know
Cyclospora testing requires a specific laboratory order — it is not part of a standard stool culture panel. The test is generally covered by health insurance when ordered by a physician. Treatment with TMP-SMX is inexpensive in generic form and widely available. For uninsured patients, community health centers can order the test and provide treatment.
What Happens Next
The Cyclospora outbreak season runs May through August. The FDA and CDC are continuing to investigate the food source. If a specific product or supplier is identified, a recall or public health advisory will follow. MedicalDaily will report on any identified food source or recall immediately.
The Bottom Line
One hundred forty-five people across 17 states have been confirmed sick with a parasitic infection linked to fresh produce, and no food source has yet been identified. Summer is peak season for Cyclospora. The illness is distinct from typical food poisoning: slower onset, longer duration, and treatable only with a specific antibiotic. If you develop prolonged summer diarrhea after consuming fresh greens or herbs, tell your doctor specifically to test for Cyclospora.
