Cyclospora: What It Is and How to Protect Yourself

Because the parasite needs a maturation window outside the body, direct person-to-person transmission is unlikely. You are not going to catch it from a sick family member the way you would a stomach bug. There is no need to isolate from the people you live with.

Instead, the route is what public health officials call fecal-oral: people get sick from eating food or drinking water that was contaminated with the mature parasite, usually weeks before it reached them. The contamination happens upstream, in a field or a water source, not in your kitchen.

Fresh produce is the most common vehicle. Over years of U.S. and Canadian outbreaks, the foods repeatedly implicated have included fresh herbs such as basil and cilantro, leafy greens and bagged salad mixes, berries including raspberries and blueberries, and snow peas. It's worth being precise here: those are the historical patterns. Investigators have not confirmed a source for this season's clusters, so that list describes risk categories, not a current culprit.

The parasite can contaminate drinking water, and it also turns up in recreational water. Cyclospora is resistant to chlorine, which means a chlorinated pool or splash pad is not automatically safe, and neither are lakes and rivers.

In the United States, cyclosporiasis season runs roughly from May 1 through August 31, when fresh produce consumption is highest. Outbreaks have been identified nearly every year since the mid-1990s. What makes 2026 notable is the volume and geographic spread, not the existence of the parasite.

What the illness is like

Symptoms usually begin about a week after exposure, with a range of two days to two weeks or more. That lag is part of why tracing the source is so hard: by the time someone is sick, the food they ate is long gone.

The primary symptom is watery diarrhea, sometimes described as explosive, with frequent bowel movements. Other common symptoms include loss of appetite, weight loss, stomach cramps, nausea, bloating, increased gas, fatigue, and low-grade fever. Some infected people have no symptoms at all. Left untreated, the illness can last from a few days to a month or more, and it can follow a remitting-relapsing course where symptoms seem to clear and then return.

Cyclosporiasis is usually not life-threatening, and many healthy people recover without treatment. The practical danger is dehydration from prolonged diarrhea, which is what has landed people in the hospital during this surge. Illness tends to be more severe and prolonged in immunocompromised people.

Standard stool tests for common stomach bugs often do not detect Cyclospora. A provider generally has to order testing for it specifically, and because the parasite is shed intermittently, more than one sample spaced out over time may be needed. The recommended treatment, according to the FDA, is the antibiotic combination trimethoprim-sulfamethoxazole, sold as Bactrim or Septra. Alternatives for people with sulfa allergies are less well established and should be worked out with a clinician.

How to protect yourself

You can lower your risk meaningfully, but washing alone cannot guarantee the parasite is gone. The FDA is direct that chlorine rinses and store-bought produce washes do not kill Cyclospora, and the parasite gets into produce upstream, long before it reaches you. Cooking is the only step that reliably kills it. With that in mind, the standing recommendations from the CDC, FDA, and state health departments are:

1. Wash your hands with soap and water before and after handling raw produce, and after using the restroom. The CDC lists this first for a reason.
2. Rinse all fruits and vegetables thoroughly under running water before eating, cutting, or cooking. Scrub firm items like melons and cucumbers with a clean produce brush, and cut away bruised or damaged spots. Produce labeled "prewashed" does not need to be washed again at home.
3. When you can, cook produce that has historically been linked to outbreaks. Michigan's health department advises heating food to 158°F to kill the parasite. Cooking is the one measure that works completely.
4. Be cautious with recreational water. Because Cyclospora resists chlorine, avoid swallowing water from pools, splash pads, lakes, and rivers, and consider steering clear of public swimming areas if there's an active outbreak where you live.
5. If you're traveling to a region where cyclosporiasis is endemic, know that routine chemical disinfection of food or water is unlikely to kill the parasite.
6. If you develop watery diarrhea that lasts more than a couple of days, especially with significant fatigue, appetite loss, or weight loss, see a healthcare provider, and specifically ask whether you should be tested for Cyclospora. Because standard panels miss it, saying the name matters.

How we think about this at LifeStraw

The work of investigating these clusters and finding the source belongs to the CDC, the FDA, and state and local health departments. The most useful thing we can do is be accurate about what's happening and clear about what any single precaution can and can't do.

Reading a story like this, it's easy to want to reduce it to a personal checklist: washing a certain way, cooking a certain way, etc. Those steps worth doing, but you can't fully protect yourself at the sink. Prevention was supposed to happen before the food ever reached you, on the farm and in the water it was grown with.

When produce arrives already contaminated, the burden shifts onto the person washing it, and a rinse was never going to be enough. The FDA's Cyclospora Action Plan exists precisely because the durable fix is upstream: better detection in produce, soil, and agricultural water, and prevention on the growing side. That's the part of this that individuals don't control, and it's the part that matters most.

Where to go for accurate information

Food-safety situations move quickly, and case counts change by the week. For the current picture and the underlying science, primary sources are the best place to start:

• CDC: Surveillance of Cyclosporiasis (updated case counts)
• CDC: Clinical Overview of Cyclosporiasis
• CDC: Symptoms of Cyclosporiasis
• CDC: Preventing Cyclosporiasis
• FDA: Cyclospora Prevention, Response and Research Action Plan
• Your state or local health department, which will have guidance specific to where you live