A sudden stomach bug can quickly disrupt your day and leave you feeling weak and exhausted. Recently, the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) flagged an unexpected spike in digestive illnesses across the country. Public health monitors have traced this surge to a microscopic, single-celled parasite that is spreading much faster than usual this summer.
This stomach trouble is caused by Cyclosporiasis, an intestinal infection linked to the parasite. While summer typically brings some cases, several states are currently reporting infection rates well above their normal seasonal levels. Michigan has been hit the hardest, with nearly 1,000 confirmed cases since late June. In response, federal investigators are tracking shipments of fresh produce to identify the exact source of the contamination. To help keep your home safe, here is how this parasite affects your body and how you can protect your family.
What is Cyclospora?
Cyclosporiasis is an intestinal disease caused by a small single-celled parasite called Cyclospora cayetanensis, which is spread through food and water. It is a microscopic organism that affects the human digestive system, causing weeks of debilitating gastrointestinal distress. It is a highly seasonal infection that typically emerges in the warm, humid summer months, when environmental conditions are conducive to parasite development.
This parasite’s history in the United States shows significant issues for today’s food safety system. Cyclospora was identified as a leading cause of large foodborne outbreaks by the Centers for Disease Control and Prevention (CDC) in the mid-1990s. Since then, there has been a consistent and worrisome rise in the number of cases reported each year by public health departments.
Cyclospora has a complex genetic structure, unlike that of most common bacterial pathogens, such as Salmonella or E. coli, which would allow for easier and faster tracking of outbreaks through genetic sequencing networks, according to PMC.
Standard DNA sequencing tools, such as PulseNet, which can effortlessly trace the bacterial fingerprint in near real time, cannot be applied in the same way to this parasite. The complexity means that it takes shoe-leather epidemiology and careful investigation to solve outbreaks, with detailed food questionnaires.
What’s happening in your body
After an individual unwittingly ingests the Cyclospora parasite, its complex, destructive life cycle begins in the human gastrointestinal tract. The infective stage of the parasite is in the stomach, where it is a protected, microscopic capsule known as an oocyst. This capsule is very hard, and the pathogen passes straight through the stomach’s strong acid to the small intestine, where it remains unharmed.
As it enters the warm, richly nourished small intestine, a scene worthy of a science fiction movie starts to unfold. The oocysts disintegrate, and the active forms burrow into the intestine’s fine cellular wall. Within these human cells, the parasites change into male and female forms to mate.
This internal reproductive cycle leads to significant mechanical and inflammatory injury to the adjacent gut tissues. The multiplying parasites burst out of the host cells, leaving behind scarred, highly inflamed tissue with reduced capacity to absorb water and nutrients. This cellular damage causes an abrupt increase in bowel fluid and can result in very loose stools and severe cramps.
Causes of Cyclospora
All symptoms of Cyclospora are attributed to ingesting water or raw food directly contaminated with mature, infective oocysts from human feces. That’s because it cannot multiply outside a living host, so the parasite has to enter your kitchen via contaminated agricultural products and/or recreational water systems.
The Food and Drug Administration (FDA) says that transmission of the parasite is almost always indirect. The oocysts are not contagious when an infected person excretes the parasite’s eggs in the stool. They need to be outside the body and in warm, moist environmental conditions to mature and become fully infective in days or weeks.
This required period of maturation means you usually will not catch Cyclosporiasis directly from a family member or coworker through casual contact at home or at work. Rather, outbreaks occur when contaminated water enters swimming areas or is released into farm fields, where it is then washed into public swimming areas.
What foods are Cyclospora found in?
Cyclospora oocysts are highly sticky and tough, allowing them to stick to the surfaces of fresh produce, which are so complex. Multi-state outbreaks are most often caused by raw fruits and vegetables that are hard to wash thoroughly.
Since the mid-1990s, the CDC and the FDA have maintained historical records of food vehicles associated with large summer outbreaks. The types of food most commonly linked to known outbreaks are:
Fresh raspberries: Linked to 12 distinct historical outbreaks, as their bumpy, fuzzy skin traps the microscopic eggs tightly.
Fresh basil: Responsible for 11 major outbreaks due to its delicate, creased leaves.
Pre-packaged salad mixes: Associated with eight outbreaks, frequently involving commercial vegetable trays, shredded lettuce and coleslaw.
Fresh cilantro: Linked to six outbreaks, often tracing back to open fields irrigated with contaminated water.
Mixed berries and fruit platters: Responsible for six documented outbreaks across various states.
The FDA’s Coordinated Outbreak Response and Evaluation Network (CORN) is actively conducting traceback investigations as part of the 2026 outbreak response. Investigators are prioritizing white onions, green onions, cucumbers and fresh cilantro to limit possible sources associated with clusters in restaurants.
Health risks and complications
For people with healthy immune systems, Cyclosporiasis is rarely deadly; however, a prolonged infection can pose significant health risks and physical problems. The signs and symptoms of this parasitic infection differ from those of typical bacterial food poisoning, which clears up in a couple of days.
“It’s just more watery diarrhea, occurring more than three times a day, accompanied by feeling bloated, full and uncomfortable,” explains Dr. Rebecca Schein, an infectious disease expert at Michigan State University Health Care. She describes the persistent bloating as feeling like you just ate a massive Thanksgiving dinner every single day.
This serious watery diarrhea can readily last for six weeks or more if untreated, creating a life-threatening clinical dehydration state and resulting in a quick weight loss if untreated. In people with weakened immune systems, such as those receiving active chemotherapy for cancer or those with HIV, the body can’t get rid of the parasite. Among these susceptible groups, the infection can cause persistent diarrhea that may persist until specific medical treatment is administered.
What to do about Cyclospora symptoms
If you have suffered from a very intense diarrheal condition that has lasted longer than three to five days, you need to take active steps to control your health and get the correct diagnosis. Do not think that treating diarrhea with a common over-the-counter anti-diarrheal remedy will eliminate the infection.
The absolute priority in any prolonged diarrheal illness is to maintain systemic hydration/electrolyte levels. To replace fluids lost through the bowel, drink lots of clear broths, oral rehydration solutions or clean water.
Dr. Justus Rabach, MD, tells Blavity Health, “Avoid using plain tap water, and opt for a diluted vinegar rinse when washing bumpy, delicate fruits such as fresh raspberries or blackberries. Place in a large bowl with one part white vinegar and three parts clean water, and stir by hand for one minute. Vinegar water can effectively and visibly rid sticky Cyclospora eggs from irregular surfaces more than running water can.”
When to see a doctor
If you have had diarrhea for more than five days, or if you have symptoms within two days of a meal at a facility associated with an established cluster of illnesses, you should seek medical attention right away. This parasite is very hard to diagnose, so you must make a specific request to your healthcare provider, as it is not detected in routine hospital stool tests.
“Normally, when doctors look for the cause of a stomach bug, they check a patient’s stool with a multiplex panel test, but Cyclospora is not on those standard panels,” warns Dr. Schein.
Your doctor needs to specifically request a special test that uses a special stain to look for the pathogen, known as an ova and parasite stool test. The special stain in this laboratory is used to color the parasite’s microscopic eggs, so they appear bright pink or orange under the microscope. However, the parasite has intermittent egg output, so health departments recommend that doctors collect up to three stool samples 24 hours apart to ensure the results are as accurate as possible.
Treatment of infection is relatively easy once a diagnosis has been made. It can be treated with a special combination antibiotic named trimethoprim-sulfamethoxazole; trimethoprim-sulfamethoxazole is sold commercially as Bactrim and Septra, according to StatPearls. This focused remedy helps by completely removing the Cyclospora infection’s ability to use vitamin folate to generate cellular energy, securely neutralizing the infection over a standard seven to ten day treatment.
How contagious is Cyclospora?
Cyclosporiasis is not directly transmitted by being near an infected person or by sharing a bathroom, since the unripe oocysts in fresh human feces must mature in the environment for several weeks before becoming infectious, says the Cleveland Clinic.
A broader environmental loop is needed for true transmission to occur, in which human waste enters agricultural fields, irrigation pipes or public parks. That’s why public health officials don’t target individual quarantines and instead concentrate on commercial food supplies and agricultural water testing, as these are environmental needs.
Bottom line
With the huge Cyclospora outbreak in 2026, it’s clear how easily this microscopic parasite can contaminate fresh produce and cause debilitating, watery diarrhea and bloating for weeks. Since routine hospital stool panels do not detect this special pathogen, the physician must order an acid-fast stain test to obtain an accurate diagnosis. With a focus on targeted antibiotic treatment and proper produce-washing practices, people can recover from the infection and keep their families safe.
Frequently Asked Questions
Who is most at risk for Cyclospora?
While anyone can contract the parasite by eating contaminated food, individuals with weakened immune systems, young children and older adults face the highest risk for severe, long-lasting symptoms and dangerous dehydration.
Which parasite causes the most deaths?
According to global epidemiological mortality tracking datasets maintained by the World Health Organization, Plasmodium falciparum, the primary parasite responsible for causing malaria, claims more human lives annually than any other parasite on Earth.
Citations
Goodman B. Michigan hits nearly 1,000 cases of diarrhea-causing parasite, as more people are infected across several states. CNN. Published July 7, 2026. Accessed July 9, 2026. https://edition.cnn.com/2026/07/07/health/cyclosporiasis-parasite-symptoms-causes
Barratt JLN, Park S, Nascimento FS, et al. Genotyping genetically heterogeneousCyclospora cayetanensisinfections to complement epidemiological case linkage. Parasitology. 2019;146(10):1275-1283. doi:10.1017/s0031182019000581
Center for Food Safety and Applied Nutrition. Cyclospora. U.S. Food and Drug Administration. Published 2019. Accessed July 9, 2026. https://www.fda.gov/food/foodborne-pathogens/cyclospora
Kemnic TR, Coleman M. Trimethoprim Sulfamethoxazole. NIH.gov. Published November 28, 2022. Accessed July 9, 2026. https://www.ncbi.nlm.nih.gov/books/NBK513232/
Cleveland Clinic. Cyclosporiasis: Symptoms, Diagnosis, Treatment, & Prevention. Cleveland Clinic. Published August 24, 2022. Accessed July 9, 2026. https://my.clevelandclinic.org/health/diseases/17957-cyclosporiasis
