Cyclospora Parasite Cases Explode as the CDC Plays Catch-Up

We tried very hard not to write about the Cyclospora parasite. So many news organizations were already covering this intestinal infection that we wondered what The People’s Pharmacy could possibly add.

Then we received this message from Lydia:

“Hello Joe & Terry Graedon,

“Would you please address the cyclospora parasite in your newsletter or podcast? It is all over the news and I wonder why there is such a delay in revealing or identifying the source. To me, this parasite sounds like the norovirus which appears to be quite common, particularly on cruises.

“Why do you think the media are making such a fuss over this bug and how does it differ from the norovirus?

“Thank you kindly and I appreciate and respect you both.”

Lydia

How could we turn away from Lydia?

Her questions are excellent. Why are thousands of people suddenly developing prolonged, sometimes explosive diarrhea? Why hasn’t anyone identified the contaminated food? How does cyclosporiasis differ from norovirus? And why did it take federal health officials so long to sound the alarm?

How Bad Is the Cyclospora Parasite Surge?

On July 14, 2026, the Centers for Disease Control and Prevention (CDC) issued a nationwide Health Alert Network (HAN) advisory about domestically acquired cyclosporiasis:

CDC Health Advisory: Domestically Acquired Cyclosporiasis Cases

Since May 1, the CDC had received reports of:

• 1,645 confirmed domestically acquired cases
• More than 5,100 additional cases requiring further analysis
• Cases reported from 34 states
• 141 hospitalizations
• No reported deaths

By roughly the same point in 2025, only 249 cases had been reported nationally. The confirmed number for 2026 was therefore more than six times higher—and it did not include the thousands of suspected cases still being investigated.

That is not a minor seasonal uptick.

The CDC warns that the actual number of illnesses is probably much higher. Many people never seek medical care. Some doctors may not think to test for Cyclospora. Routine stool examinations may miss the parasite, and reports can take weeks to travel from doctors and laboratories through state health departments to federal officials.

Michigan has been hit especially hard. Ohio and nearby areas have also reported large numbers of illnesses. The CDC is investigating several clusters, including an outbreak involving more than 400 people in Michigan, Ohio, Kentucky and West Virginia.

That suggests we may not be dealing with one contaminated shipment from one unlucky farm. Several different outbreaks could be occurring at the same time.

So far, no single food, grower, supplier, restaurant or retailer has been confirmed as the source of the nationwide surge.

What Is the Cyclospora Parasite?

Cyclospora cayetanensis is a microscopic parasite. People become infected after consuming food or water contaminated with the organism.

There is an important twist in its life cycle. When Cyclospora first leaves an infected person in feces, it is not yet capable of infecting someone else. It must mature in the environment for days or weeks before becoming infectious.

That is why cyclosporiasis is not usually passed directly from one person to another. It is primarily a food-and-water contamination problem rather than the highly contagious person-to-person infection we see with norovirus.

Cyclospora cases usually rise during spring and summer. The CDC considers May 1 through August 31 the annual “cyclosporiasis season.”

Previous American outbreaks have been linked to fresh produce such as:

• Lettuce and salad mixtures
• Cilantro
• Basil
• Raspberries
• Snow peas
• Green onions

That does not mean all these foods are dangerous or that any one of them has been confirmed as the source of the current outbreak.

Why Can’t Investigators Find the Source of the Cyclospora Parasite?

Tracking Cyclospora is a public-health nightmare. Symptoms usually begin about one week after exposure, but they can appear anywhere from two days to two weeks or longer. Can you remember every salad, sandwich, garnish, berry, smoothie, herb and restaurant meal you consumed during the last 14 days? Most people cannot.

Fresh produce also passes through a complicated supply chain. Lettuce from several farms may be combined at one processing plant and distributed to supermarkets, restaurants and institutional kitchens across several states. A salad kit may contain ingredients from multiple growers or even multiple countries.

By the time someone becomes sick, seeks medical attention, receives the right laboratory test and is interviewed by a health department, the suspicious bag of greens may be long gone.

The testing itself presents another problem. A routine ova-and-parasite examination may not reliably detect Cyclospora parasites. Doctors often must specifically request a Cyclospora stool test or a molecular gastrointestinal panel that includes the parasite. In some cases, more than one stool specimen may be needed.

Investigators are trying to assemble a puzzle while many of the pieces are missing.

Lydia Asks: Is the Cyclospora Parasite Like Norovirus?

At first glance, Lydia’s comparison makes sense. Both infections can cause miserable gastrointestinal symptoms, including diarrhea, nausea, cramps and dehydration.

But the two troublemakers behave very differently.

Norovirus Is the Contagious Sprinter

Norovirus is a highly contagious virus. It spreads through contaminated food or water, but it also moves remarkably easily from one person to another. That is why norovirus can rip through cruise ships, nursing homes, schools, restaurants and entire families.

An infected person can shed billions of viral particles in vomit and stool. It takes only a tiny number of particles to make someone else sick. Those particles may contaminate hands, food, bathroom fixtures, doorknobs, countertops and serving utensils.

Symptoms usually begin suddenly, about 12 to 48 hours after exposure. The classic attack involves nausea, forceful vomiting, watery diarrhea and abdominal pain.

Readers of The People’s Pharmacy have described the experience as an “intestinal apocalypse.” One reader reported alternating between sitting and kneeling in the bathroom for hours. Another described simultaneous vomiting and diarrhea as a “cataclysmic explosion.”

The ordeal can be horrendous, but most people recover within one to three days.

There is no medicine that eliminates norovirus. Treatment consists primarily of replacing fluids and electrolytes. Some people become so dehydrated that they need intravenous fluids.

You can learn more about norovirus at this link.

Cyclospora Is the Foodborne Marathoner

Cyclospora is a parasite, not a virus. It is generally acquired from contaminated food or water and is unlikely to pass directly from one sick person to another. Instead of striking within a day or two, Cyclospora usually waits about a week before announcing itself.

The hallmark is frequent watery diarrhea. Other symptoms can include:

• Loss of appetite
• Weight loss
• Bloating and gas
• Abdominal cramps
• Nausea
• Profound fatigue
• Low-grade fever

Vomiting sometimes occurs, but it is less common than with norovirus.

Untreated cyclosporiasis may last for a few days, several weeks or more than a month. The symptoms may improve and then return, sometimes repeatedly.

Unlike norovirus, cyclosporiasis has a specific treatment. Doctors generally prescribe trimethoprim-sulfamethoxazole, also known as TMP-SMX, Bactrim or Septra, for seven to 10 days. The quicker the diagnosis, the better, so that treatment can be maximally effective.

Norovirus Versus Cyclosporiasis at a Glance

Here is our simplest way of describing the difference:

Norovirus is an intestinal apocalypse that usually strikes fast and burns out within a few days. Cyclosporiasis is more of a slow-motion siege. It may take a week to appear and can drag on or keep returning for a month or longer.

That answers another part of Lydia’s question: Why are the media making such a fuss?

Norovirus is notorious, but most attacks end within a few days. The Cyclospora parasite can be difficult to diagnose, difficult to trace and exhausting to endure. This year’s extraordinary number of illnesses—and the inability to identify the source—makes the story especially alarming.

Did the CDC Drop the Surveillance Ball?

Here is where this story becomes especially frustrating.

The CDC operates the Foodborne Diseases Active Surveillance Network, better known as FoodNet. Since the 1990s, this program has worked with selected states, the Food and Drug Administration and the Department of Agriculture to monitor important foodborne infections.

But on July 1, 2025, required FoodNet surveillance was narrowed to only two pathogens: Salmonella and Shiga toxin-producing E. coli (aka STEC). Monitoring Cyclospora, Campylobacter, Listeria, Shigella, Vibrio and Yersinia became optional.

Some states, including Michigan, continued tracking Cyclospora. Others were no longer required to do so.

CIDRAP (Center for Infectious Disease Research and Policy) reported on the surveillance reduction at this link:

It later reported that Cyclospora cases were increasing while the CDC lagged in compiling national figures:

On July 9, CIDRAP noted that the CDC’s most recent public update listed only 145 national cases through June 16. Five days later, the agency’s Health Alert Network advisory acknowledged 1,645 confirmed cases and more than 5,100 additional illnesses requiring analysis. That is quite a modification.

We cannot say that cutting surveillance caused the outbreak. Reducing data collection did not contaminate lettuce, cilantro, berries or irrigation water. But weakening an early-warning system can make it harder to recognize an emerging crisis, compare one state with another and connect clusters that initially appear unrelated. FoodNet was created to detect just such signals.

The official Cyclospora season began May 1. Some state health departments were reporting extraordinary increases by late June. The CDC did not issue its national Health Alert Network advisory until July 14.

Why did doctors, laboratories and consumers have to wait until the middle of July for such a warning? And why did federal officials weaken routine tracking for this parasite only one year before the nation experienced an unprecedented surge? Public-health surveillance should be a little like a smoke alarm. It can seem unnecessary and expensive—right up until the house catches fire.

Why Are Cyclospora Cases Exploding This Year?

As far as we can tell, no one yet knows. That alone is disappointing.

Several possibilities deserve investigation:

• One widely distributed food product may be contaminated.
• Several unrelated outbreaks may be occurring simultaneously.
• Contaminated irrigation or processing water may have affected produce.
• Greater awareness and improved testing may be finding illnesses that once went undiagnosed.
• Differences in reporting among states may make some areas look more affected than others.
• Reduced federal surveillance may have delayed recognition of the national pattern.

The role of water should not be overlooked. Human waste can contaminate irrigation water, processing water or fields. Produce may then carry the parasite to consumers. Until investigators identify a source, blaming a particular farm, country, restaurant chain or food company would be irresponsible.

The combination of soaring cases, incomplete surveillance and an unidentified source deserves more than a casual oops.

What Foods Deserve Extra Caution to Avoid Cyclospora Parasites?

No federal agency has advised people to stop eating a specific fruit or vegetable.

Based on previous outbreaks, however, foods that deserve particular attention include:

• Bagged lettuce and salad mixtures
• Fresh cilantro
• Fresh basil
• Green onions
• Snow peas
• Raspberries and other delicate berries

These foods are often eaten raw and may contain folds, crevices or delicate surfaces that are difficult to clean completely. There is no evidence that one particular company is especially vulnerable. The greater concern is produce that is eaten raw, handled extensively or combined from multiple sources.

People who are older, immunocompromised or especially vulnerable to dehydration may choose to be extra cautious until the source is identified. Cooked vegetables and fruits that can be washed and peeled may offer some reassurance.

We are not recommending that people abandon fruits and vegetables. Their health benefits remain enormous.

Can You Wash the Cyclospora Parasite Off Produce?

Everyone should wash fresh produce thoroughly under clean running water. Washing can remove dirt and reduce some kinds of contamination. Unfortunately, it is not a force field.

Cyclospora can cling stubbornly to leafy vegetables, berries and herbs. The CDC warns that chemical disinfectants or produce sanitizers may not fully eliminate it. During this outbreak, the agency recommends washing produce even if the package says it was pre-washed.

Practical precautions include:

• Wash your hands with soap and water before and after handling produce.
• Rinse fruits and vegetables thoroughly under clean running water.
• Separate the leaves of lettuce and rinse them individually.
• Scrub firm produce such as cucumbers and melons with a clean brush.
• Remove bruised or damaged areas.
• Consider whole heads of lettuce instead of mixed salad kits.
• Peel fruits and vegetables when practical.
• Refrigerate cut produce promptly.
• Keep knives, cutting boards, countertops and refrigerator drawers clean.
• Cook produce when feasible. Adequate heat kills Cyclospora.

Do not wash fruits or vegetables with bleach, detergent or household disinfectants. Those chemicals are not intended to be swallowed.

Is Farmers’ Market Produce Safer?

Not automatically. But we are big fans of farmers markets! A local farmers market may offer something a supermarket often cannot: an opportunity to talk directly with the person who grew the food.

Useful questions include:

• Did you grow this produce yourself?
• What water was used for irrigation?
• Was manure used, and was it properly composted?
• How was the produce washed after harvesting?
• Has it been kept cool?

Contaminated water or unsafe handling can affect a backyard garden, a family farm or an international producer.

How Can You Tell Where Produce Came From?

Look for a country-of-origin statement on the package, sticker, produce bin or nearby sign. Federal rules require many large retailers to identify the country of origin for fresh fruits and vegetables.

There are significant gaps, though. Restaurants rarely provide this information. Mixed salads may contain ingredients from several sources. A numerical sticker generally identifies the type of produce but does not reveal the farm, irrigation source or complete path through the supply chain.

When the label is unclear, ask the produce manager. Avoiding produce simply because it came from a particular country is not justified at this time. Officials have not identified one nation, farm, company or supplier as the source of the current surge.

When Should You Seek Medical Help?

Contact a healthcare professional if you develop:

• Watery or unusually frequent diarrhea lasting more than a few days
• Diarrhea that improves and then returns
• Significant fatigue or loss of appetite
• Unexplained weight loss
• Dizziness, extreme thirst or reduced urination
• Severe symptoms if you are older, very young or immunocompromised

Tell the clinician about salads, herbs, berries and other uncooked produce consumed during the previous two weeks. Most important, ask whether a Cyclospora-specific stool test is appropriate. A routine ova-and-parasite examination may miss the organism. PCR-based testing may improve detection.

People who are prescribed TMP-SMX should make sure their physician and pharmacist know about all their other medications. This drug can interact with warfarin and certain blood pressure medicines. It can also raise potassium levels in susceptible patients. Here is an article we have written about this dangerous drug interaction.

A Deadly Drug Interaction Often Ignored by Doctors and Pharmacists
An interaction between the commonly prescribed antibiotic co-trimoxazole and blood pressure drugs such as lisinopril or valsartan can cause sudden death.

The People’s Pharmacy Bottom Line

Lydia wanted to know why the media are making such a fuss.

The answer is that the Cyclospora parasite is not merely another version of the familiar cruise-ship bug. Norovirus spreads with astonishing ease, strikes suddenly and usually disappears within a few days.

Cyclospora is generally acquired from contaminated food or water, may hide for a week before symptoms begin and can cause diarrhea that continues or keeps returning for a month or longer. The number of Cyclospora cases in 2026 is extraordinary. Thousands of additional illnesses are still being evaluated, and the source remains unknown. Meanwhile, the federal warning system appears to have been playing catch-up after required surveillance for this parasite was made optional.

Consumers should not panic or swear off produce. They should handle it carefully, recognize the symptoms and seek medical attention for persistent or recurring watery diarrhea. They also deserve a food-safety surveillance system capable of sounding the alarm before thousands of people have already become sick.

A small favor, please. If you found this article informative, please pass it along to family and friends. There is a lot of confusion around this outbreak. Because there is an available treatment, people should know what to do if they suspect they have come down with cyclosporiasis. Thank you for supporting our work.