Cyclospora vs. crypto: Why these summer parasites are making headlines
July 20, 2026
By Neima Briggs, M.D., Ph.D.,
Assistant Professor of Internal Medicine
in the Division of Infectious Diseases and Geographic Medicine
You’ve seen the alarming headlines about parasites causing “explosive diarrhea” across the U.S. Two microscopic parasites – cyclospora cayetanensis and cryptosporidium – can both cause prolonged gastrointestinal illness, including watery diarrhea, stomach cramps, and dehydration.
But they spread in different ways, affect different populations, and require different approaches to diagnosis and treatment.
Cyclospora is more commonly known as the "diarrhea parasite" linked to fresh produce outbreaks. A nationwide surge in cyclospora infections has prompted investigations by the Centers for Disease Control and Prevention (CDC), with more than 1,600 laboratory-confirmed cases and thousands of additional suspected cases reported across 34 states, including Texas. Health officials believe the true number is likely much higher because many people do not seek medical care or get specialized testing.
Cryptosporidium, often called "crypto," is one of the most common causes of recreational water illness and can spread through swimming pools, splash pads, lakes, and water parks. Infections from this parasite also are on the rise, with small outbreaks reported across the country, including in Florida and the San Antonio, Texas, area.
These parasites typically don’t show up on many routine stool tests. Your healthcare provider may need to order advanced laboratory testing and talk with an infectious disease specialist if they suspect either infection.
But there is good news: Most healthy people recover fully. Knowing what symptoms to watch for and when to see a healthcare provider can help you feel better sooner.
What are cyclospora and cryptosporidium?
Although these microscopic intestinal parasites both cause watery diarrhea, cyclospora and cryptosporidium spread in different ways.
Cyclospora: The produce-associated parasite
Cyclospora is responsible for the outbreak currently making the most headlines. Unlike many stomach bugs, cyclospora infects only humans. It spreads when food or water becomes contaminated with human waste.
Fresh produce such as leafy greens, herbs, berries, and other fruits and vegetables have been linked to previous outbreaks. The CDC reports that some illnesses are believed to be linked to shredded lettuce used by fast-food restaurants in five states, but investigations are ongoing to identify other sources of illness in other areas that are unrelated to this outbreak.
Cyclospora doesn’t spread directly from one person to another. After leaving the body, the parasite spends one to two weeks maturing in the environment before it becomes infectious. That means contaminated soil or water used for irrigation can introduce the parasite to crops before they reach your plate.
Cryptosporidium: The waterborne parasite
Cryptosporidium is much more common year-round and is a leading cause of waterborne diarrheal illness in the U.S. Unlike cyclospora, crypto can spread:
- Through contaminated recreational water, such as pools, splash pads, lakes, and water parks. It is resistant to chlorine.
- From person to person.
- From infected animals to people.
- Through contaminated food or drinking water.
Related: Read "What causes GI issues in teens – and how to get them to talk about it"
What are the symptoms, and who is most at risk?
Infections from either parasite usually cause:
- Bloating
- Fatigue
- Loss of appetite
- Nausea
- Stomach cramping
- Watery diarrhea, which can sometimes be severe
While “explosive diarrhea” has become the headline symptom, the hallmark is that both types of infection tend to last longer than other stomach illnesses. Symptoms may improve then return and can continue for weeks if left untreated.
When should you call the doctor?
Many stomach illnesses improve within a few days. However, parasitic infections tend to have longer-lasting symptoms. Contact your healthcare provider if:
- Diarrhea lasts more than four to five days
- Symptoms improve, then come back
- You feel dehydrated or can’t keep up with fluids
- Fatigue disrupts your normal activities
- You have a weakened immune system
- You develop bloody diarrhea, a high or persistent fever, severe abdominal pain, confusion, fainting, or other concerning symptoms. These are not typical of cyclospora or cryptosporidium infection and may indicate another illness requiring prompt evaluation.
Most healthy adults recover without hospitalization. However, symptoms can be more severe or prolonged in people who:
- Have weakened immune systems
- Have received an organ transplant
- Take chemotherapy or immunosuppressive medications
- Have inflammatory bowel disease or another chronic intestinal inflammation
Not every case of diarrhea is caused by cyclospora or cryptosporidium. Many common viral, bacterial, and other gastrointestinal illnesses, such as norovirus, cause similar symptoms. Getting an accurate diagnosis is key before starting treatment.
How are cyclospora and cryptosporidium infections treated?
Preventing dehydration is the most important treatment for both illnesses. Because diarrhea can cause significant fluid and electrolyte loss, patients should drink fluids frequently. Oral rehydration solutions such as Pedialyte can be especially helpful when diarrhea is frequent because they replace both fluid and electrolytes.
Monitor your hydration by paying attention to how often you’re urinating rather than aiming to drink a specific number of ounces each day. Generally, you should be urinating about every four to six hours while you’re recovering. Avoid caffeine and alcohol during recovery, as both can worsen dehydration.
Prescription treatment options depend on which parasite is causing your illness:
- Cyclospora is typically treated with the antibiotic trimethoprim-sulfamethoxazole.
- Cryptosporidium often resolves on its own in healthy adults. Anti-parasitic medications may be recommended for people with prolonged symptoms or weakened immune systems.
How can you reduce the risk of infection?
Cyclospora and cryptosporidium may be making headlines this summer, but they don’t have to derail your plans. A few precautions can go a long way toward reducing your risk of infection:
- Consider using local produce if there are no outbreaks in your community.
- Wash your hands before preparing food.
- Rinse fresh fruits and vegetables thoroughly under running water.
- Remove outer leaves from lettuce and cabbage. Separate leafy greens so water reaches all surfaces.
- Wash and vigorously scrub your fruits and vegetables thoroughly under running water before eating, cutting, or cooking, even if the produce is labeled “pre-washed.”
- Cook produce when appropriate, as heat kills the parasite.
- When swimming, avoid swallowing pool or splash pad water. Do not swim while you have diarrhea. If you are diagnosed with or suspected of having cryptosporidium, stay out of recreational water for two weeks after the diarrhea has completely stopped because the parasite can continue to spread after symptoms resolve, even in chlorinated pools.
While headlines can be alarming, remember: most people who get infected with cyclospora or cryptosporidium fully recover, and there are effective treatments for people with prolonged or more severe illness. As public health officials continue to investigate the current outbreaks, recommendations may evolve. Follow guidance from trusted sources such as your doctor and local health department to help you stay informed about outbreaks.
To talk with an expert about possible cyclospora or cryptosporidium infections, make an appointment by calling 214-645-6427 or request an appointment online.
