What is cyclosporiasis—and how can you avoid infection?

Starting in May 2026, thousands of cases of “explosive diarrhea” across 32 states have been caused by cyclospora, a type of microscopic parasite that spreads through contaminated food or water. Each year in the United States, there are about a dozen cyclospora outbreaks, resulting in between 200 and 1,000 infections (called cyclosporiasis). The latest outbreak is significantly larger than usual, with more than 3,000 cases confirmed or under investigation, predominantly in Michigan as well as Ohio, Illinois, and New York.

How do people become infected? Is it dangerous? And is there a way to avoid getting sick? Here are answers to these and other important questions about this intestinal infection.

What is cyclospora?

Cyclospora is a type of parasite known as a protozoan. Parasites are organisms that rely on their host to multiply and spread. Since they need their host to live, parasitic infections are usually not fatal, but they often cause harm, or uncomfortable symptoms.

Cyclospora invade cells of the small intestine, consuming the food their host is digesting as well as their host’s body fluids. Cyclospora infection, or cyclosporiasis, is usually not life-threatening. But the illness does cause gastrointestinal (GI) distress that can range from mild to severe.

What are the symptoms of cyclosporiasis?

Since cyclospora infects the small intestine, people who are infected usually experience digestive issues, which may include:

• Watery diarrhea
• Frequent and sometimes explosive bowel movements
• Loss of appetite
• Weight loss
• Gas and bloating
• Extreme tiredness or fatigue
• Low-grade fever
• Stomach cramps
• Nausea
• Vomiting
• Muscle aches

After exposure, symptoms usually develop within one week. But GI issues can arise anywhere from two days to two weeks after becoming infected. Some people with cyclosporiasis may not develop any symptoms.

How does cyclospora spread?

Cyclospora spreads through food or water that is contaminated with feces (poop). If you eat food or drink water that is contaminated with the parasite, you can become infected. You can also become infected if you:

• Swallow contaminated pool, hot tub, or lake water
• Use contaminated water to grow or wash produce
• Use poop to fertilize produce

There’s no evidence that cyclospora spreads directly from person to person. So, you can’t get this infection from touching or being in contact with another person who is infected. If more than one person in a household is infected, they likely consumed the same contaminated food or water.

Who is at greatest risk?

Cyclospora is most commonly found in tropical and subtropical regions, such as Central America, South America, Asia, and Africa. People living or traveling in these regions are more likely to be affected.

In the U.S., the parasite mainly spreads through imported, raw produce. Seasonal domestic outbreaks tend to occur during the spring and summer. In the U.S., previous cyclospora outbreaks were linked to the following fruits and vegetables:

• Basil
• Cilantro
• Mesclun lettuce
• Raspberries
• Snow peas
• Sweet peas

How is cyclosporiasis diagnosed and treated?

A cyclospora infection is diagnosed with a stool (poop) test. In a lab, a poop sample is examined under a microscope to determine if the parasite is present.

People with healthy immune systems may recover from cyclosporiasis on their own. But if left untreated, the infection may linger for days or even weeks. For some people, symptoms may seem to go away but then come back later. This can happen more than once. Those with chronic health issues or a weakened immune system are at higher risk for an ongoing or more severe infection.

The infection can be treated effectively with antibiotics. Healthcare providers usually prescribe a combination antibiotic called trimethoprim-sulfamethoxazole, also known as Bactrim, Septra, or Cotrim. For those with a sulfa drug allergy, ciprofloxacin or nitazoxanide may be used.

There are other ways people who are infected can help ease their symptoms and prevent complications, such as:

• Rest.
• Drink plenty of fluids, such as water, sports drinks, or broth, to avoid dehydration and electrolyte imbalances that can result from diarrhea.
• Avoid caffeinated drinks and alcohol.
• Take antibiotics as directed by your healthcare provider—even after symptoms improve.

With proper diagnosis and treatment, most people feel better within two weeks. But occasional bouts of diarrhea may continue for up to a month.

If your symptoms return, do not improve with treatment, or they are severe (you have several bouts of watery diarrhea daily), it’s important to see your healthcare provider (HCP). Seek immediate medical attention if you have signs of severe dehydration, including:

• Confusion
• Dizziness
• Very dark urine (pee) or you are urinating less often than usual

Is it possible to avoid or prevent cyclospora infection?

The best way to avoid cyclospora infection is to not consume contaminated food or water. To kill the cyclospora parasite on fresh produce, you must heat food to 158°F (70°C) or higher, as cold temperatures, washing, and chemical sanitizers may not be effective.

Generally, you should also be mindful about food preparation and storage. Be sure to follow food safety recommendations, including:

• Wash your hands with soap and water after using the bathroom and before, during, and after handling or preparing food.
• Wash all cooking surfaces, dishes, and utensils with soap and hot water.
• Wash all fresh produce, including herbs, fruits, and vegetables before eating, peeling, cutting, and cooking—even if you plan to peel them or remove rinds.
• Cut off any damaged or bruised areas on fruits and vegetables before preparing and eating.
• Refrigerate cut, peeled, or cooked fruits and vegetables as soon as possible (within two hours).
• Avoid swimming if you have diarrhea. And wait at least two weeks to swim after you’ve recovered.
• Drink water from sources you know to be safe, such as sealed bottled water, boiled tap water, and carbonated water from sealed cans. Avoid water or food that may be contaminated.