Cyclospora Outbreak: What People with Cancer Should Know

In the United States, federal and state health officials are tracking an outbreak of a microscopic parasite called Cyclospora. As of July 19th, this outbreak has been linked to iceberg lettuce distributed by the brand Taylor Farms. 

Cyclospora causes a gastrointestinal illness called cyclosporiasis. This causes severe diarrhea, which can lead to dehydration. It is especially dangerous for older adults, children, and anyone who is immunocompromised, including from cancer or cancer treatment. Learn what symptoms of Cyclospora infection to watch for, how to protect yourself, and when to call your doctor. 

What are the symptoms of a Cyclospora infection?

The primary symptom of a Cyclospora infection is frequent, watery diarrhea. Because the parasite disrupts how your small intestine absorbs water and nutrients, it can cause a cluster of other uncomfortable digestive symptoms.

Common signs of a Cyclospora infection include:

• Painful abdominal cramps
• Stomach bloating
• Nausea
• Excessive gas
• Loss of appetite
• Weight loss

Cyclospora does not usually cause vomiting or fever, though some people can present with flu-like symptoms. Some people have no symptoms. 

Unlike typical bacterial food poisoning, which makes you sick within hours, Cyclospora has an incubation period. It usually takes about 2 to 14 days after eating contaminated food for symptoms to actively appear.

How is Cyclospora spread?

Cyclospora is spread from feces (poop). Most often it is spread through contaminated water or produce that has been watered or washed with contaminated water. 

What is the source of the July 2026 Cyclospora outbreak?

Currently, an open investigation has linked a multistate Cyclospora outbreak to shredded iceberg lettuce. More than 1,644 cases have been reported across five states, resulting in 94 hospitalizations. Knowing how to spot the symptoms of this infection and take preventive steps can help keep you safe during your recovery.

The contaminated lettuce from this Cyclospora outbreak seems to come from Taylor Farms-brand lettuce sourced from central Mexico. The lettuce was distributed to stores and restaurants in multiple states between June 29th and July 16th, and has been officially recalled. The lettuce was sold under several different brand names. 

This case is still under investigation. There may be more details about this outbreak and its source as the investigation continues. Check the U.S. Food and Drug Administration for updates on this outbreak. 

What are common food sources of Cyclospora?

Past outbreaks of Cyclospora have been linked to:

• Basil
• Broccoli
• Cabbage
• Cilantro
• Leafy greens
• Parsley
• Pre-cut salad mixes
• Raspberries
• Snow peas
• Sugar snap peas

You can also get Cyclospora from contaminated water, but this is most common outside of the United States. 

When to call your doctor if you have diarrhea during cancer treatment

For patients undergoing treatments like chemotherapy, targeted therapies, or radiation, diarrhea is already a common side effect. You should contact your care team if:

• More than 6 bowel movements in 24 hours
• Diarrhea lasting more than 24 to 48 hours
• Diarrhea that wakes you from sleep
• Blood in your stool or on the toilet paper after wiping
• Fever
• Painful cramps

One of the complications of diarrhea is dehydration. Watch for: 

• Less frequent urination
• Dark urine
• Dry mouth and lips
• Thirst
• Dizziness, weakness, and/or confusion
• Headache
• Appetite loss
• Fatigue

How to test for Cyclospora

It is important to tell your doctor if you have eaten any foods that are a part of an ongoing Cyclospora outbreak. Routine stool tests frequently miss this specific parasite. If you are experiencing watery diarrhea that lasts for more than a few days, take these steps:

• Reach out to your primary oncologist or physician. Do not attempt to self-treat with standard over-the-counter anti-diarrheal medications without their direct guidance.
• Inform your provider if you suspect exposure. Doctors must specifically request a gastrointestinal PCR panel or a targeted Cyclospora test. Conventional parasite checks do not reliably detect it.
• If you test positive, the illness is easily treatable with a standard 7- to 10-day course of a prescription antibiotic (trimethoprim-sulfamethoxazole). This effectively clears the parasite.
• You may need to come into the clinic for additional treatment, including IV fluids or monitoring.

How to avoid Cyclospora infection 

Cyclospora is difficult to remove from produce once it’s contaminated. Pre-washed and pre-cut produce are at a higher risk of contamination. Standard rinsing may not get rid of Cyclospora, and it is resistant to sanitizers. Cooking produce to 158 degrees Fahrenheit or 70 degrees Celsius is the best option, especially if you are immunocompromised. 

To avoid infection with Cyclospora and other bacteria:

• Avoid known sources of contaminated produce.
• Wash your hands with warm, soapy water for 20 seconds before handling produce.
• Discard outer layers of produce.
• Rinse produce with clean running water, even if you plan to peel it or if it has a rind.
• Use a produce brush or rub the skins of fruits and vegetables.
• Avoid cross-contamination. Wash kitchen surfaces after cutting produce with hot soapy water.
• Cook produce when possible.
• When eating at restaurants, avoid sources of contaminated produce if possible or only order cooked foods.
• Follow any other specific instructions from your care team. 

If you are currently experiencing an immune-compromised health or on an intense chemotherapy cycle, your doctor may advise temporarily sticking to thoroughly cooked vegetables, soups, or thick-skinned fruits that can be peeled. 

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Sources:

1. U.S. Centers for Disease Control and Prevention (CDC) Outbreak Notice: "Multistate Outbreak of Cyclospora Infections Linked to Shredded Iceberg Lettuce" (July 26, 2026). https://www.cdc.gov/cyclosporiasis/outbreaks/07-26/index.html
2. UC Davis Health News Headline: "Cyclospora: The tiny parasite behind explosive diarrhea cases" (July 2026). https://health.ucdavis.edu/news/headlines/cyclospora-the-tiny-parasite-behind-explosive-diarrhea-cases/2026/07
3. U.S. Food and Drug Administration (FDA) Outbreak Investigation: "Investigation of a 5-State Outbreak of Cyclospora Illnesses Linked to Iceberg Lettuce" (July 2026). https://www.fda.gov/food/outbreaks-foodborne-illness/investigation-5-state-outbreak-cyclospora-illnesses-iceberg-lettuce-july-2026?utm_medium=email&utm_source=govdelivery
4. Reuters Healthcare Report: "FDA says Taylor Farms Cyclospora finding was false positive" (July 20, 2026). https://www.reuters.com/business/healthcare-pharmaceuticals/fda-says-taylor-farms-cyclospora-finding-was-false-positive-2026-07-20/
5. U.S. Centers for Disease Control and Prevention (CDC) Investigation Details: "Outbreak Investigation of Cyclospora Illnesses: Iceberg Lettuce" (July 2026) https://www.cdc.gov/cyclosporiasis/outbreaks/07-26/investigation.html
6. Cleveland Clinic Medical Diseases Reference: "Cyclosporiasis: Causes, Symptoms, Treatment & Prevention" (2026). https://my.clevelandclinic.org/health/diseases/17957-cyclosporiasis