Cyclosporiasis: The Stomach Infection That's on the Rise
- 13 hours ago
- 7 min read
Background
Cases of cyclosporiasis, a parasitic illness that causes stomach problems, are spreading quickly in the United States, and no one is sure why. Almost every summer, we get a few relatively minor cyclosporin outbreaks in the US, but this summer has seen a significantly higher number of cases. There is a wider geographic spread (18-32 states). Michigan has been hit especially hard. Information obtained from the Michigan Department of Health and Human Services site on 7/13/2026 reports 2,640 confirmed and probable cases (this number differs from the CDC's, as the latter's reporting lags behind by several weeks). Other states are quickly catching up. They are seeing more clusters of these outbreaks than they normally see (see the USA Today cases in the US map, 7/13/26).
Transmission
Cyclospora are parasites that typically live in environments where soil or water has been contaminated with human feces (poop). They are not naturally present in clean U.S. soil or water. And numbers usually increase a bit in the summer. This summer, we are facing an inordinately high number of cyclospora-related illnesses. The parasites are contaminating something in our food supply. Patterns from past outbreaks suggest that contaminated fresh imported produce is the most likely source, particularly because it is common-even endemic - in many tropical and subtropical areas. Though rare, U.S.-associated outbreaks have occurred in the past. In any case, people are getting sick from these products, and the problem is spreading fast.
When Cyclospora spreads to people, it is usually through contaminated food and/or drinking water. But even with product tracing, the CDC and state health departments still don’t know which specific product is responsible for this year’s outbreak. No single restaurant, grocery chain, farm, or supplier has been linked to the illnesses. Because the source has not been identified, stopping the spread is difficult.
Produce most commonly linked to Cyclospora outbreaks include the following:
Basil
Cilantro
Spinach (occasionally)
Iceberg lettuce (less common)
Romaine lettuce
Mesclun lettuce/spring mix
Traditional mixes: arugula, frisée, baby lettuce, radicchio, spinach
Modern mixes: chervil, mâche (lamb’s lettuce), endive, tatsoi, mustard greens, other leafy varieties
Raspberries
Snow peas
Sweet peas
Prepackaged produce is more often the culprit than individually sold produce. Fresh vegetables from produce markets are generally a safer bet.
It is important to note that you cannot see Cyclospora because it is a microscopic parasite — far too small to detect with the naked eye. Contaminated produce looks completely normal: no spots, slime, discoloration, or odor. The texture, color, and smell of vegetables or fruits do not change, and there is no obvious residue.
SYMPTOMS
About a week after exposure, if a person has ingested something contaminated with Cyclospora, they often develop the following symptoms:
Watery, sometimes “explosive,” diarrhea (often 6+ stools/day) — prolonged beyond 24–48 hours
Stomach cramps
Gas and bloating
Nausea, and sometimes (though less often) vomiting
Loss of appetite
Possible weight loss (no, this is NOT the diet you want to be on!)
Fatigue
Without treatment, cyclosporiasis can last weeks to months, often with symptoms that come and go. With proper treatment, recovery is typically much quicker.
Those at greater risk for developing severe symptoms include:
Individuals with underlying risk factors (very young or older age, diabetes, altered immunity, and other conditions that weaken the body’s ability to fight infection)
People who are not in good overall health or who do not take care of themselves (poor nutrition, dehydration, unmanaged chronic illness, or inadequate rest can worsen the course of illness)
Diagnosis
Diagnosis usually involves two key steps:
A clinician will typically obtain a detailed history of the illness, asking about recent foods eaten, travel, symptom timing, and any possible exposures.
Stool testing
Specific testing for Cyclospora (this must be ordered intentionally — it is not included in routine stool tests).
Molecular assays such as PCR‑based gastrointestinal multiplex panels can detect Cyclospora when included.
Important: The standard ova and parasite (O&P) test does not detect this parasite, which is why cases are often missed at first.
Approaches to Treatment and Care
Empiric Treatment
Empiric treatment (treating based on symptoms before test results are available) can be initiated with antibiotics if testing is delayed or unavailable. However, it is not generally recommended because unnecessary antibiotic use can cause other problems. A clinician should guide this decision.
Prescription Medications
TMP‑SMX (Bactrim) is the first-line treatment. A sulfa‑based medication.
Ciprofloxacin (Cipro) is less effective than TMP‑SMX but is sometimes used as a second‑line option.
Ondansetron (Zofran) helps with nausea and vomiting.
Over‑the‑Counter Medications
Loperamide (Imodium) can help slow diarrhea. This is supportive care only — it does not kill the parasite. Should not be used if there is fever, bloody stools, or signs of severe illness. When unsure, speak with a primary care provider.
Supportive Care
-Hydration
Drink plenty of water in small, frequent sips. Dehydration can cause severe illness, especially in children, older adults, and immunocompromised patients.
Signs of dehydration include:
Dizziness
Dry mouth
Reduced urination
Feeling faint
Rapid heart rate
Sunken, dark eyes
-Electrolytes
Diarrhea causes loss of electrolytes like sodium and potassium, which can lead to additional medical problems.
Helpful electrolyte sources:
Pedialyte
Low‑sugar sports drinks
WHO oral rehydration packets (available at pharmacies — ask a pharmacist)
If you have a known electrolyte imbalance, speak with your primary care provider.
Foods naturally containing electrolytes:
Bananas
Potatoes
Broths
Yogurt (if tolerated)
-Recommended Diet
Low‑fiber foods help reduce bowel stimulation and may slow diarrhea.
Gentle foods:
White rice
Plain pasta
Toast
Saltine crackers
Oatmeal
Cream of wheat
Bananas
Applesauce
Boiled potatoes
Soft scrambled eggs
Lean proteins:
These help maintain strength while ill:
Chicken (boiled or baked)
Turkey
White fish
Tofu
Foods to AVOID
High‑fiber foods (raw vegetables, salads, bran, legumes)
Greasy or fried foods
Spicy foods
Dairy (if it worsens symptoms)
Caffeine
Alcohol
High‑sugar drinks (can worsen diarrhea)
Prevention
-Washing
Washing produce does not reliably remove Cyclospora — it may reduce contamination, but it cannot eliminate it.
Still, general food‑safety washing is helpful:
Wash all produce thoroughly under running water.
Choose whole heads of lettuce or leafy greens rather than prewashed, bagged mixes.
Remove and discard the outer 2–3 leaves.
Wash inner leaves individually under running water.
Do not soak produce (soaking can spread contamination).
-Peeling
Peeling fruits and vegetables can reduce surface contamination, but it does not guarantee removal of Cyclospora.
-Cooking
Cooking is the only reliable kill step for Cyclospora.
Heat food to an internal temperature of 158°F (70°C).
This temperature instantly inactivates the parasite.
Cyclospora is a heat‑sensitive parasite, so proper cooking is highly effective.
-Avoidance
Because Cyclospora cannot be seen, smelled, or tasted, avoidance strategies focus on reducing exposure:
Be cautious with prepackaged salad mixes during outbreak season.
Choose whole, unprocessed produce when possible.
Follow public health updates about ongoing outbreaks and implicated foods.
When in doubt, cook produce rather than eating it raw.
What Can You Eat Without Worrying About Cyclospora Contamination?
The following vegetables and fruits have no known history of Cyclospora contamination and are considered low‑risk, especially when washed and, when appropriate, cooked (1).
Leafy greens
Bagged salads
Mesclun mixes
Cilantro
Basil
Parsley
Snow peas
Raspberries
Blackberries
Certain imported berries
Some pre‑cut produce mixes
Complications and Prognosis
-Possible complications include:
Severe dehydration from prolonged diarrhea, leading to dizziness, weakness, rapid heart rate, and reduced urination.
Electrolyte imbalance: Loss of sodium, potassium, and other electrolytes can cause muscle cramps, irregular heartbeat, or worsening fatigue.
Weight loss and malnutrition due to prolonged diarrhea, nausea, and reduced appetite.
Prolonged or relapsing illness: Symptoms may improve and then return if untreated.
Secondary complications, such as worsening of underlying medical conditions (diabetes, heart disease, kidney disease).
Rare complications
Cyclospora does not typically cause bloodstream infections, organ failure, or long‑term damage. Severe outcomes are uncommon but can occur in people who cannot maintain hydration or who have significant immune compromise.
-PROGNOSIS
With treatment (TMP‑SMX):
Most people recover quickly, often within a few days.
Symptoms usually resolve completely.
Relapses are uncommon once treatment is completed.
Without treatment:
Illness can last weeks to months.
Symptoms may wax and wane.
Dehydration and fatigue can become significant.
People may struggle to maintain normal daily activities.
Long‑term outlook:
Cyclospora does not cause chronic infection.
It does not remain in the body once symptoms resolve.
No long‑term organ damage is expected.
Prognosis is excellent with proper hydration and appropriate antibiotics.
Questions??
Can a person spread Cyclospora to another person?
No. Cyclospora oocysts shed in stool are not infectious until they mature in the environment for days to weeks.
This means:
Changing a diaper is not a risk.
Household contact is not a risk.
Cyclospora cannot be passed directly from person to person.
Even if someone is infected today, the parasite they shed cannot infect anyone until it has matured for a while outside the body.
Does vinegar kill Cyclospora?
No. Vinegar may reduce bacteria, but Cyclospora oocysts are resistant to:
Vinegar
Lemon juice
Salt water
Soap
Household disinfectants
Typical produce washes
Cooking reliably destroys Cyclospora.
Are frozen foods okay?
Yes. Cyclospora has never been linked to commercially frozen foods in CDC outbreak investigations.
-Frozen foods with no known Cyclospora history:
Frozen vegetables
Frozen fruits
Frozen mixed produce
Frozen meals
Commercially frozen berries
-Why frozen foods are safe
Freezing prevents Cyclospora from maturing into an infectious form.
Many frozen foods are blanched before freezing, which further reduces the risk of contamination.
CDC outbreak history shows zero frozen food involvement.
Do plants absorb parasites into their leaves?
No. Plants do not absorb Cyclospora through their leaves. Cyclospora stays on the surface of produce — it does not enter leaf tissue, veins, or the plant’s internal water system.
Can Cyclospora spread from one garden to another?
Yes — but only through environmental contamination, not person‑to‑person spread. Cyclospora cannot “jump” between plants or move through the air. It can only be carried by contaminated soil or water moving from one area to another.
How could a garden become contaminated with Cyclospora?
1. Water runoff
Contaminated soil or water can wash downhill or across property lines during:
Heavy rain
Irrigation overflow
Sloped yards
2. Shared water sources
If water is contaminated upstream, multiple gardens can be exposed:
Rain barrels
Irrigation hoses
Wells
3. Soil displacement
Cyclospora oocysts can be physically moved in:
Flooding
Erosion
Digging or landscaping
4. Animals tracking soil
This is mechanical transport, not infection:
Pets
Wildlife
Birds and animals can carry contaminated dirt on their paws or feet.
5. Other contamination sources
Sewage leaks
Contaminated water sources
Inadequate farm‑worker sanitation
