The essentials

Cyclosporiasis is a gut infection caused by a tiny parasite, Cyclospora cayetanensis, picked up from contaminated fresh produce or water. Its signature is watery diarrhea that can drag on for weeks, come back after you feel better, and leave you very tired. A routine stool parasite exam often misses it: the doctor has to ask the lab for a Cyclospora test (a special stain or a PCR). It is treatable, and most healthy people recover. Signs of severe dehydration need urgent care.

What is Cyclospora disease, at a glance?

  • Medical name: cyclosporiasis, an infection of the small intestine by the single-celled parasite Cyclospora cayetanensis[2][9].
  • How common in 2026: an unusually large season. CDC counted 20,996 laboratory-confirmed cases acquired in the United States with symptoms starting between May 1 and August 31, 2026, including 1,161 hospitalizations and 2 deaths, against 1,180 cases over the same months of 2025[5].
  • Main source in 2026: processed iceberg lettuce from Taylor Farms de Mexico, linked to 12,883 cases in 21 states; CDC declared this outbreak over on September 11, 2026[6].
  • Key tests: a stool test that specifically targets Cyclospora: modified acid-fast stain, UV fluorescence microscopy or PCR[3].
  • Contagious? Not directly from person to person: the parasite needs at least one to two weeks outside the body before it can infect anyone[2].

What are the symptoms of cyclosporiasis?

Symptoms usually start about one week after the contaminated meal, with a range of about 2 days to 2 weeks or more[1]. This delay is why many people cannot remember what made them sick.

  • Most typical: watery diarrhea with frequent bowel movements, sometimes explosive[1][9].
  • Often present: loss of appetite, weight loss, stomach cramps, bloating, more gas, nausea and fatigue that can be marked[1].
  • Less common: vomiting, body aches, headache and a low-grade fever[1].
  • Pattern over time: without treatment, illness can last from a few days to a month or longer. Diarrhea may stop and then return, and tiredness can persist after the gut settles[1][2].

Some infected people have no symptoms at all, especially in regions where the parasite is common[2]. Stool looks watery rather than a specific color: the parasite is invisible to the naked eye. Blood in the stool is not a typical feature and calls for a medical opinion, as described in our page on visible blood in stool.

When should I see a doctor for Cyclospora symptoms?

When to see a doctor

  • Emergency: call 911 or go to the emergency room for signs of severe dehydration: confusion, fainting, no urine for many hours, or a young child, older adult or person with a weakened immune system who cannot keep fluids down[1][9].
  • Within 24 to 48 hours for watery diarrhea several times a day that does not settle, dizziness, a dry mouth or extreme thirst, severe stomach pain, or new diarrhea when your immune system is weakened[9].
  • At your next appointment if diarrhea keeps returning, you are losing weight, or you were treated and still do not feel better[9].

What causes Cyclospora infection and who is at risk?

The parasite infects only humans. People who are sick pass immature forms, called oocysts, in their stool. These must mature in the environment before they can infect someone, so infection happens when food or water is contaminated with human feces, for example through irrigation water, sewage problems or poor hygiene during harvesting[2][9].

  • Common Eating raw fresh produce linked to US outbreaks: leafy greens and salad mixes, cilantro, basil, parsley, berries and snap peas[9]. In the United States, outbreaks occur mostly in spring and summer[9].
  • Common Living in or traveling to tropical and subtropical regions, where the parasite is endemic[2].
  • Possible Drinking untreated water; routine water treatment is unlikely to kill the parasite[7][12].
  • Rare Complications: malabsorption, gallbladder inflammation (cholecystitis) and reactive arthritis[2]; Guillain-Barré syndrome has also been reported after infection[12].

Anyone can be infected. Young children, older adults and people with a weakened immune system are more likely to become severely ill, mainly because of dehydration[1].

Which stool test detects Cyclospora?

Diagnosis rests on a stool sample. The trap is that most US laboratories do not look for Cyclospora routinely, even when stool is sent for parasites. CDC asks health care providers to request Cyclospora testing specifically[3]. MedlinePlus puts it plainly: standard stool tests do not detect this parasite[9]. Laboratory guidance adds that these extra stains may have to be ordered separately from the usual ova and parasites exam[11].

  • Modified acid-fast stain: oocysts take the dye unevenly, from unstained and wrinkled to pink, red or purple[3].
  • UV fluorescence microscopy: oocysts glow blue or green under ultraviolet light, a sensitive screening method[3].
  • PCR: detects the parasite's DNA. Many labs use gastrointestinal multiplex panels, but not all panels include a Cyclospora target[3].

Infected people may shed only a few oocysts, so several samples collected on different days can be needed[3]. Collect them before taking anti-diarrheal medicine or antibiotics[9]. Here is a fictitious report showing why one "negative" line does not settle the question.

Fictitious example of a stool report (United States format)
TestResultReferenceFlag
Ova and parasites, concentrate and trichromeNo ova or parasites seenNone seenN
Cyclospora / Cryptosporidium, modified acid-fast stainCyclospora oocysts seenNone seenA
GI pathogen panel, PCR: Cyclospora cayetanensisDetectedNot detectedPOS
GI pathogen panel, PCR: Salmonella, Campylobacter, norovirusNot detectedNot detectedN
  1. Ova and parasites "none seen": no parasites or eggs were seen in the sample examined[10]. But this standard exam does not rule out Cyclospora, which often needs a separate stain or a molecular test[3][11].
  2. Modified acid-fast line: the same stain looks for Cryptosporidium. Cyclospora oocysts measure about 8 to 10 micrometers, roughly twice the size of Cryptosporidium (4 to 6), which helps the lab tell them apart[3].
  3. "Detected" on a PCR panel: the parasite's DNA was found. Check that your panel lists Cyclospora at all: if it is absent from the list, the panel says nothing about it[3].
  4. Other lines negative: common bacteria and viruses were not found. A stool culture or other tests may still be added depending on your symptoms.

Stool panel results with a mix of "detected", "not seen" and acid-fast lines? BloodSense explains each line of your complete report in plain words and helps you prepare questions for your doctor.

Explain my stool test report

Can blood tests show cyclosporiasis?

No blood test identifies Cyclospora. When diarrhea is heavy or long-lasting, a doctor may order an electrolyte panel or a basic metabolic panel to check sodium, potassium and kidney function, which are the numbers dehydration affects. Other stool markers such as fecal leukocytes or calprotectin look at inflammation of the gut and do not name the germ.

How do doctors tell Cyclospora from other causes of diarrhea?

Many infections start the same way. Clues that point a doctor toward Cyclospora are watery diarrhea that lasts more than a few days or keeps returning, marked tiredness and weight loss, recent travel to tropical regions, and a known outbreak[3][9]. A short bout of vomiting and diarrhea that clears in a day or two is more typical of viral gastroenteritis. Diarrhea after antibiotics raises the question of C. difficile. When symptoms go on for months without an infection being found, conditions such as irritable bowel syndrome may be considered, but only after the right stool tests have been done.

How is cyclosporiasis treated?

No doses are given here: your doctor chooses the treatment and its length.

  • Treatment of choice: CDC recommends the antibiotic combination trimethoprim-sulfamethoxazole (TMP-SMX), with separate courses for adults and children[4]. Most people improve within a few days of starting it. Finish the course even if you feel better, or the illness may come back[9].
  • Sulfa allergy: CDC notes there is no highly effective alternative. Options include close observation with symptom care, other medicines with limited evidence, or, in selected cases assessed by an allergist, desensitization[4].
  • Weakened immune system: a longer course may be needed[4].
  • Pregnancy and young babies: the treatment is used in pregnancy only when the expected benefit outweighs the risk, and generally not in infants under 2 months[4].
  • Fluids first: rest and oral rehydration drinks; intravenous fluids if dehydration is severe. Use anti-diarrheal medicine only after asking a provider, and never give it to children. If you take diuretics or ACE inhibitors, ask whether to pause them while you have diarrhea[9].

Most healthy people would eventually recover even without antibiotics, but the illness can last weeks and relapse, which is why testing and treatment are worthwhile[4].

How long does it last, and what follow-up is needed?

With treatment, symptoms usually ease within days; without it, they can last weeks to months[9]. A repeat stool test is not routine. Your doctor may test again if diarrhea returns after treatment, if you have a weakened immune system, or if symptoms persist. Relapse and reinfection are both possible[2][12]. Keep a simple diary: number of stools per day, weight, fluids, and any new symptom.

How can I prevent Cyclospora infection?

  • Wash your hands with soap and water before and after handling raw fruits and vegetables[7].
  • Rinse produce under running water before eating, cutting or cooking it, and scrub firm items such as melons and cucumbers with a clean brush. No soap or bleach[7][9].
  • Remember that washing alone does not remove the parasite reliably: cooking produce to at least 158 °F (70 °C) kills it[7].
  • Remove the outer leaves of leafy greens, cut away bruised parts, and refrigerate cut produce within two hours[7][9].
  • Follow food recall alerts and throw away recalled products[7].
  • When traveling to tropical regions, drink safe water and avoid food prepared in unsanitary conditions. There is no vaccine[9].

Questions to ask your doctor

  1. Was my stool tested specifically for Cyclospora, and by which method?
  2. Does the panel used by the lab include Cyclospora?
  3. Should I send more samples on different days if the first one is negative?
  4. Do I need blood tests to check for dehydration?
  5. Which treatment do you recommend, and what if I am allergic to sulfa drugs?
  6. What should I do if the diarrhea comes back after treatment?

Frequently asked questions

Can I catch Cyclospora from someone in my house?

Direct spread is unlikely, because the parasite has to mature outside the body for one to two weeks before it becomes infectious[2]. Good handwashing and not preparing food for others while you have diarrhea remain sensible.

Can I get cyclosporiasis more than once?

Yes. Symptomatic reinfection can occur[2], although repeat infections tend to be shorter[12].

Is Cyclospora the same as Cryptosporidium?

No. Both are parasites that cause watery diarrhea and can show up on the same acid-fast stain, but they are different organisms, of different sizes[3].

Can pets give me Cyclospora?

No. Cyclospora cayetanensis is believed to infect only humans[9].

  1. Centers for Disease Control and Prevention. Symptoms of cyclosporiasis. cdc.gov (accessed October 25, 2026)
  2. Centers for Disease Control and Prevention. Clinical overview of cyclosporiasis. cdc.gov (accessed October 25, 2026)
  3. Centers for Disease Control and Prevention. Clinical testing and diagnosis for cyclosporiasis. cdc.gov (accessed October 25, 2026)
  4. Centers for Disease Control and Prevention. Clinical care and treatment of cyclosporiasis. cdc.gov (accessed October 25, 2026)
  5. Centers for Disease Control and Prevention. Cyclosporiasis case data, 2026 season. Updated October 23, 2026. cdc.gov (accessed October 25, 2026)
  6. Centers for Disease Control and Prevention. Cyclospora outbreak linked to iceberg lettuce. Final update September 11, 2026. cdc.gov (accessed October 25, 2026)
  7. Centers for Disease Control and Prevention. Preventing cyclosporiasis. cdc.gov (accessed October 25, 2026)
  8. Centers for Disease Control and Prevention. How cyclosporiasis surveillance data are used. cdc.gov (accessed October 25, 2026)
  9. MedlinePlus Medical Encyclopedia. Cyclosporiasis. Reviewed July 30, 2026. US National Library of Medicine. medlineplus.gov (accessed October 25, 2026)
  10. MedlinePlus Medical Encyclopedia. Stool ova and parasites exam. Reviewed April 27, 2026. US National Library of Medicine. medlineplus.gov (accessed October 25, 2026)
  11. Garcia LS, Arrowood M, Kokoskin E, et al. Practical guidance for clinical microbiology laboratories: laboratory diagnosis of parasites from the gastrointestinal tract. Clin Microbiol Rev. 2017;31(1):e00025-17. doi:10.1128/CMR.00025-17 (accessed October 25, 2026)
  12. Almeria S, Cinar HN, Dubey JP. Cyclospora cayetanensis and cyclosporiasis: an update. Microorganisms. 2019;7(9):317. doi:10.3390/microorganisms7090317 (accessed October 25, 2026)

This page is general information. It does not replace the advice of a doctor, who interprets your results with your symptoms, history and examination.