Cyclosporiasis Symptoms, Treatment, and Prevention

Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis, typically contracted by eating or drinking something contaminated with infected fecal matter. It causes watery — sometimes explosive — diarrhea that can last weeks or relapse repeatedly if left untreated. The good news: it responds well to a specific antibiotic when caught and diagnosed correctly.

What Is Cyclospora and How Does It Spread?

Cyclospora cayetanensis is a single-celled parasite that lives in the human intestine. Contamination generally occurs when food or water comes into contact with human fecal material containing the parasite. Fresh produce is frequently implicated because it is often consumed raw and may be exposed to contaminated irrigation water, wash water, or environmental sources during production.

Cyclosporiasis is not transmitted through direct person-to-person contact. Infected individuals shed oocysts — the parasite's dormant eggs — in their feces, but those oocysts must mature in the environment for approximately one to two weeks before becoming infectious. That's why you can't catch it from a sick person sitting next to you.

Previous outbreaks have been linked to bagged salads, leafy greens, fresh basil, fresh cilantro, raspberries, and green onions. In July 2026, Taylor Farms recalled iceberg lettuce sourced from central Mexico as part of an ongoing multistate investigation.

Symptoms: What Cyclosporiasis Feels Like

Symptoms of cyclosporiasis typically begin about one week after exposure, though onset can occur anywhere from 2 to 14 days after being exposed.

The symptoms may include watery diarrhea (often frequent and explosive), loss of appetite, weight loss, bloating, increased gas, stomach cramps, nausea, vomiting, muscle aches, low-grade fever, and fatigue. Not all people infected with Cyclospora have symptoms.

One key feature that sets cyclosporiasis apart from a typical stomach bug: the relapsing pattern. If not treated, the illness may last anywhere from a few days to a month or longer. Symptoms may seem to go away and then return one or more times.

[REVIEWER: add clinical insight here — for example, what presentation in a patient typically raises your suspicion for Cyclospora over other causes of traveler's diarrhea or summer gastroenteritis?]

Who Is Most at Risk?

Anyone can get cyclosporiasis. Historically it was associated with travel to tropical and subtropical regions, but domestic outbreaks — often tied to imported fresh produce — are now a recurring feature of U.S. summers. CDC considers the cyclosporiasis season in the U.S. to run from May 1 through August 31.

Immunocompromised individuals, older adults, and young children face greater severity and should seek medical evaluation sooner than healthy adults. People living with HIV may also need longer courses of treatment and are at risk for more serious complications.

How Is Cyclosporiasis Diagnosed?

This is where many cases slip through the cracks. It is important that your provider specifically requests testing for Cyclospora, since it is not included in routine stool tests.

Specifically request Cyclospora laboratory testing on stool specimens because routine ova and parasite examinations might not reliably detect the parasite. Consider molecular (PCR-based) diagnostic testing where available, because it can improve detection.

Multiple stool samples may be necessary, as parasite shedding can be intermittent. Some laboratories use special staining techniques to enhance detection.

If you've had prolonged or relapsing diarrhea — especially during summer months — tell your doctor you want to be tested specifically for Cyclospora. Don't assume it's been included in a standard panel.

Treatment: The Antibiotic That Works

Trimethoprim-sulfamethoxazole (TMP-SMX), sold as Bactrim, Septra, or Cotrim, is the treatment of choice for cyclosporiasis.

Treat confirmed cases with 7 to 10 days of TMP-SMX for immunocompetent adults and children over age 2 months; consider longer courses for patients with immunocompromising conditions.

Most healthy people will eventually recover from cyclosporiasis without treatment, although their illness may be prolonged. No highly effective alternatives have been identified yet for persons who are allergic to or intolerant of TMP-SMX. If you have a sulfa allergy, tell your doctor before starting treatment so they can consult with an infectious disease specialist about your options.

Antidiarrheal medications and oral rehydration to replace lost fluids are also important supportive steps, particularly for young children and older adults who are at higher risk of dehydration.

[REVIEWER: add clinical insight here — particularly around management in immunocompromised patients or those with sulfa allergies, and when you would consider hospitalization.]

The 2026 U.S. Outbreak: What You Need to Know

Cyclosporiasis is making headlines this summer. Since May 1, 2026, CDC has received reports of over 4,000 laboratory-confirmed domestic cases, with more than 7,400 additional cases under investigation. Reporting delays are common in parasitic outbreaks, and the incubation period for Cyclospora can last up to two weeks after a consumer ingests contaminated food. The true number of cases is almost certainly higher than what's been confirmed.

Because cyclosporiasis is often underdiagnosed and underreported, the true number of illnesses is likely higher than what has been reported to CDC. Clinicians are being urged to consider it in any patient with prolonged or relapsing watery diarrhea, even without a travel history.

Prevention: What Actually Helps

Reduce your risk by thoroughly washing fresh produce under clean running water before eating and by following safe food handling practices. Be aware that chemically disinfecting or sanitizing produce might not fully eliminate Cyclospora. It is important to thoroughly wash produce even if it is labeled as pre-washed.

Standard water disinfection isn't reliable against this parasite either. Using chlorine or iodine for water disinfection is unlikely to be effective because oocysts are extremely tolerant of halogens. Travelers to tropical regions should follow food and water precautions — opting for cooked foods and treated or bottled water where possible.

There is no vaccine for cyclosporiasis.

FAQ

What are the first signs of cyclosporiasis?
The most common early symptoms include watery diarrhea, loss of appetite, bloating, nausea, and fatigue, typically beginning about one week after exposure to the parasite. Some people also experience cramping, vomiting, and low-grade fever. Symptoms can vary in severity and may initially feel like a standard stomach bug.

How long does cyclosporiasis last without treatment?
If not treated, the illness may last anywhere from a few days to a month or longer, and symptoms may seem to go away and then return one or more times. Starting the correct antibiotic (TMP-SMX) early shortens the illness and prevents relapse.

Can you get cyclosporiasis without traveling internationally?
Yes. While it was once considered primarily a traveler's illness, domestic outbreaks tied to imported fresh produce are now common in the United States every summer. Consider cyclosporiasis in patients presenting with prolonged or relapsing watery diarrhea, particularly during the May–August cyclosporiasis season, even without a history of international travel.

Is cyclosporiasis contagious from person to person?
No. Cyclospora oocysts must mature in the environment for approximately one to two weeks before they become infectious, so the parasite cannot spread directly from an infected person to those around them. Infected individuals do not need to stay home from work or school.

Will a standard stool test detect Cyclospora?
Standard stool panels will miss Cyclospora unless your provider specifically orders an ova and parasite exam with Cyclospora PCR testing. Always tell your doctor if you suspect cyclosporiasis so they can request the right test.

Practical Takeaway

If you've had watery diarrhea for more than a few days this summer — especially if it comes and goes — don't brush it off as a passing bug. Ask your doctor specifically about Cyclospora testing. The infection won't show on routine stool panels, and without the right antibiotic, it can drag on for weeks. Wash all raw produce thoroughly, even pre-washed bags, and stay alert to any active recalls from the FDA.

5. Sources

• CDC Health Alert Network (HAN), July 2026: Domestically Acquired Cyclosporiasis Cases in Multiple U.S. States —

• CDC Clinical Care of Cyclosporiasis —

• CDC Cyclosporiasis Surveillance 2026 —

• CDC Yellow Book 2024: Cyclosporiasis —

• Johns Hopkins Medicine: Cyclosporiasis Outbreak 2026 —

• Stony Brook Medicine: What to Know About Cyclosporiasis —

• New Jersey Department of Health: Cyclosporiasis FAQ 2024 —

• Giangaspero A, Gasser RB. "Human Cyclosporiasis." Lancet Infectious Diseases, 2019;

• NIH/PMC: Outbreak of Cyclosporiasis, Limestone County, Alabama 2023 —

7. Category
Infectious Disease / Food Safety

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