Cyclospora Outbreak: What to Know About Symptoms and Food Safety

The United States is in the midst of its worst year yet for cyclosporiasis, an intestinal illness caused by a parasite transmitted through food or water contaminated with human feces.

The Centers for Disease Control and Prevention has confirmed or is investigating more than 11,500 cases in 41 states — the most cyclosporiasis cases ever recorded in a single year in the United States — and it has reported 308 hospitalizations. Since the agency’s last update on July 21, state health departments have logged thousands more cases.

Federal officials are also investigating an outbreak including nearly 2,000 people in nine states — Michigan, Ohio, Indiana, Kentucky, West Virginia, Illinois, Kansas, Oklahoma and Pennsylvania — that has been linked to iceberg lettuce supplied by Taylor Farms and grown in central Mexico. On July 17, Taylor Farms recalled potentially contaminated lettuce from 27 states, including products sold to restaurants, retail stores and food service distributors, including Taco Bell and Walmart. Details on the exact products and retail outlets affected have been sparse.

The Food and Drug Administration said it was investigating several other, smaller outbreaks, including one with 72 cases, but it did not disclose their locations or potential sources.

Health officials are scrambling to understand the true size and scope of the illnesses across the country, and are investigating multiple types of produce as potential sources. The number of cases is expected to rise in the weeks ahead, they have said. It can take up to six weeks for federal and state officials to determine if an illness is linked to an outbreak, according to the F.D.A.

What is cyclospora?

Cyclospora is a microscopic parasite that infects people when they consume food or water contaminated with human feces containing its oocysts (or eggs), said Keith R. Schneider, a professor of food safety at the University of Florida.

Infections tend to rise from May through August in the United States because the parasite thrives in warm temperatures.

After the parasite is ingested, it can take from two days to two weeks or more for it to infect the intestinal lining and cause symptoms, including cramping and watery diarrhea.

An infected person will then shed the oocysts in their feces, but it takes another week or two for the parasite to become infectious outside the body. That lag most likely explains why the illness does not seem to spread directly from person to person, Dr. Schneider said.

How unusual is this outbreak?

The scale of the current cyclosporiasis outbreak is unlike any seen before in the United States, said Frank Yiannas, a food safety expert and former top official at the F.D.A.

The thousands of cases across multiple states imply a “massive degree of human fecal contamination,” said Matthew Moore, a food safety microbiologist at the University of Massachusetts Amherst.

It’s possible that tainted agricultural water is behind the unparalleled surge in infections, said Randy Worobo, a professor of food safety microbiology at Cornell. One possibility is that water used to irrigate fields or wash produce may have mixed with runoff from nearby toilet facilities, though health officials are still investigating the source of the contamination.

Michigan is currently reporting the most infections in the country: 9,680 cases and 160 hospitalizations as of Tuesday. The state typically records only 40 to 50 cases per year.

The C.D.C.’s current cyclosporiasis figures are most likely an undercount, health experts say, as some people who are ill are never diagnosed. When they are, it can take time for states to investigate cases and report them to the C.D.C., and for the agency to confirm these cases before sharing them with the public.

This helps to explain why many states report cyclosporiasis totals that do not match the C.D.C. numbers. States may also count cyclospora cases differently. For instance, some states report cases based on positive laboratory tests while others only report cases after health officials follow up with people to confirm their symptoms. Some states also update their case counts more frequently than others.

The New York Times contacted state health departments for their current case counts, which collectively exceeded 18,500 cases as of Tuesday afternoon.

The previous largest outbreak in recent decades occurred in 2020 and sickened 701 people across 14 states, according to the C.D.C. That outbreak was linked to Fresh Express bagged salads. A 2022 Florida outbreak was also linked to bagged salads.

Do we know what is causing the surge in infections?

Lettuce sold by Taylor Farms and grown in central Mexico likely accounts for many — but not all — of the reported illnesses this year, health officials have said.

Nearly 2,000 cases have so far been linked to iceberg lettuce supplied by Taylor Farms and served at Taco Bell locations in nine states. But Taylor Farms has also recalled bagged lettuce sold at Walmart and shipped to a number of food service distributors in 27 states, so the affected lettuce may have reached restaurants, cafeterias or other establishments that have not yet been publicly named.

On July 23, for instance, health officials in New Hampshire reported that nine people had become ill after eating Taylor Farms lettuce at a medical center cafeteria.

The current surge in infections may be a result of multiple outbreaks happening simultaneously, said Kalmia Kniel , a microbiologist at the University of Delaware.

In North Carolina, which had recorded 718 cases as of July 27, people have frequently reported consuming parsley and cilantro before becoming ill. Some who have become ill in Michigan reported eating at restaurants, including fast food chains, but not everyone reported eating out, said Natasha Bagdasarian, the chief medical executive for Michigan.

Because it can take up to a few weeks or more for people to develop symptoms and get diagnosed, public health investigators often ask people what they ate during the weeks before they became ill, which can be difficult for people to remember, Dr. Bagdasarian said.

Cyclospora is a “tricky” organism to study, Dr. Kniel said. It’s challenging to detect in food or water. And compared with other pathogens like bacteria, it’s harder to link cases from a common source using genetic analysis.

Previous cyclospora outbreaks in the United States have been linked to lettuce and salad mixes, raspberries, basil, cilantro, fruit mixes, snow peas and snap peas.

Produce is probably contaminated in fields or in processing facilities, Dr. Bagdasarian said, and a supplier selling a product like bagged lettuce to restaurants may also be stocking grocery stores with it.

How risky is fresh produce?

Some health experts are recommending that people take extra precautions with produce that has been implicated in past outbreaks — especially bagged lettuce.

Whether you choose to avoid certain types of fresh produce right now comes down to your own risk tolerance, said Barbara Kowalcyk, director of the Institute for Food Safety and Nutrition Security at George Washington University. She said that she was avoiding higher risk items for the time being. “Quite honestly, I don’t have time in my life for explosive diarrhea,” she said.

Cyclospora isn’t typically life-threatening, but lengthy bouts of diarrhea can cause severe dehydration, which is especially dangerous for those in vulnerable groups, including children, older adults and people who are pregnant or otherwise immunocompromised.

Telling healthy people outside of those groups to avoid entire categories of fresh produce is an “overly broad” recommendation, said Craig Hedberg, a professor of environmental health sciences at the University of Minnesota School of Public Health. Doing so could result in people eating less healthfully and food waste, he said.

Some public health departments are advising people to cook higher-risk produce to at least 158 degrees. This is a more reliable way to kill the parasite than rinsing or freezing.

Health officials in Michigan are advising people to use whole heads of lettuce rather than bagged salad kits, toss the outer two or three layers of leaves and then rinse with water.

In fact, all fresh produce should be rinsed before eating, health officials recommend. Scrub firm fruits and vegetables like melons and cucumbers with a clean brush, and cut away any damaged or bruised areas. When feasible, peel produce before eating.

What are the symptoms?

The most common symptom of cyclosporiasis is watery diarrhea. The illness can also cause a loss of appetite, cramping, bloating, gas, nausea, fatigue and weight loss. Some people may experience a low-grade fever, said Dr. Adam Ressler, an infectious disease physician with Michigan Medicine.

People with symptoms should see a health care provider for testing and treatment, Dr. Ressler said. “I wouldn’t wait too long to get in and get tested,” he said.

Without treatment, symptoms can last anywhere from a few days to a month or more. And they may “wax and wane,” he said.

How is cyclosporiasis treated?

The most effective treatment for cyclosporiasis is Bactrim (a combination oral antibiotic also sold under the brand names Septra and Cotrim). It’s typically taken for seven to 10 days, Dr. Ressler said.

For those who are allergic to or intolerant of that medication, a doctor can recommend other treatment options, such as different types of antibiotics, he said.

Untreated, symptoms like chronic diarrhea can last for a month or more, Dr. Ressler said.

Staying hydrated is important, said Dr. Thomas Moore, a clinical professor of medicine at the University of Kansas School of Medicine-Wichita. He recommended making a simple rehydration solution with water, sugar and salt to replace electrolytes and fluids.

Are federal health cuts hampering the response?

It’s possible. State and local health departments rely on federal funds to monitor, detect and respond to food-borne illnesses. In 2026, those agencies received only about 40 percent of what they requested for those efforts, Dr. Kowalcyk said.

During the coronavirus pandemic, state health departments received emergency federal funding to support their response to the virus. Many of those departments used that money to improve their ability to respond to other types of future outbreaks. That stream of funding has since ended, Dr. Kowalcyk said, resulting in many staff and program cuts.

Last summer, the C.D.C. quietly scaled back its Foodborne Diseases Active Surveillance Network, or FoodNet, which made it optional for the 10 member states to track cyclospora cases and report them to the C.D.C. While those states still have other ways to report infections, experts say that this change may result in many cases going uncounted.