How The Cyclospora Parasite Spreads—And How To Protect Yourself

Explosive diarrhea, stomach cramps, nausea and fatigue. Thousands of people in at least 34 states have fallen ill with cyclosporiasis, a parasitic food-borne infection.

Health officials have reportedly identified shredded iceberg lettuce from Mexico supplied by Taylor Farms to Taco Bell restaurants as a potential source of the outbreak, but it may not be the only cause.

Forbes expert healthcare contributors have been tracking the outbreak. Here, they explain how the illness spreads and what you can do to protect yourself.

What Is Cyclosporiasis?

Cyclosporiasis is an infection caused by a tiny parasite called cyclospora cayetanensis, the biologist and Forbes contributor Victoria Forster writes.

“In the U.S. cyclosporiasis has repeatedly been linked to contaminated fresh produce that has come into contact with feces,” Forster writes, adding: “Previous outbreaks have been associated with imported and domestically grown leafy greens, basil, cilantro, raspberries and packaged salad mixes, often eaten raw.”

Forster notes that “cyclosporiasis remains relatively uncommon in the U.S. compared to more common sources of food poisoning caused by bacteria,” but there have been other similar outbreaks before.

Read more: Poop Parasite Causes Hundreds Of Cases Of Explosive Diarrhea

What Are The Causes?

The parasite spreads through contaminated food or water, often when irrigation or wash water has been contaminated with human waste.

Many of the latest cases have been traced to iceberg lettuce at Taco Bell restaurants in Indiana, Kentucky, Michigan, Ohio, and West Virginia, according to the CDC.

Dr. Judy Stone, a Forbes senior contributor and infectious disease specialist, writes that produce grown in the United States relies heavily on irrigation systems.

“This is important because surface water can be easily contaminated, and it doesn’t take many organisms to cause infection,” Stone says. “Contamination can occur from leaking septic and sewer systems, and from people’s waste and garbage⁠.”

Read more: It’s The Water Likely Driving Cyclospora Outbreaks

How Do You Get Cyclosporiasis?

“Most people get infected after drinking contaminated water or eating contaminated food,” writes Dr. Omer Awan, a physician and Forbes senior contributor on public health. “It is not usually spread person-to-person.”

The illness can affect anyone, but those with weakened immune systems are more likely to develop severe or prolonged illness, including children, older people, people who are pregnant, people with chronic medical conditions and those on chemotherapeutic drugs.

“Their bodies may not be able to fight off the infection as effectively as healthier adults with strong immune systems,” Awan says.

Cyclosporiasis remains most common in the summer because “the parasite thrives in warmer, humid climates,” Awan adds. “It needs heat to mature before infecting humans.”

And hotter weather may be making outbreaks worse.

“It’s possible that the decades-long trend of rising temperatures globally is contributing to the more frequent presence of diseases more typically found in tropical regions,” writes Joshua P. Cohen, Forbes senior contributor for health policy.

Read more: Possible Role Of Climate Change In Current Cyclosporiasis Outbreak

How to Avoid Getting Cyclosporiasis?

Washing your hands thoroughly (at least 20 seconds) and washing your food when preparing to eat are simple practices that can help reduce the risk of cyclosporiasis, experts say.

This doesn’t kill the parasite, but Awan says washing can displace it and “remove up to 90% of the parasite particles.”

“If purchasing produce, washing and scrubbing the produce with water as well as refrigerating it as soon as you return home can reduce the growth of the parasite that causes cyclosporiasis,” he says. But it’s not a guarantee.

“The only way to eliminate the parasite from produce is by cooking it at a temperature of 158 degrees Fahrenheit,” Awan writes. “This effectively kills the parasite.”

Read More: How To Stay Healthy Amid The Growing Cyclosporiasis Outbreak

What Happens If You Get Cyclosporiasis?

Expect prolonged diarrhea, stomach cramps, nausea and fatigue. This can all lead to dehydration.

“Symptoms generally appear about a week after exposure, but can appear as soon as two days or as late as two weeks after ingesting the parasite,” Forster says. Most cases resolve on their own but some can be serious.

“Treatment is available with an anti-parasitic drug called trimethoprim-sulfamethoxazole, which is effective for most patients,” she writes.

Be cautious; “If diarrhea lasts more than three days, you should go see your doctor,” Awan advises.

When Will the Outbreak Subside?

The number of cases in the U.S. is growing and though public health officials have traced the source behind some of the outbreak, there may be others. That’s led some public health experts to wonder about monitoring protocols.

“The difficulty of the investigation has renewed debate over recent cuts to foodborne disease surveillance and public health funding by the current U.S. government on both the state and federal level,” Forster writes.

She cites 2025 cuts to the CDC’s Foodborne Diseases Active Surveillance Network, or FoodNet, a collaboration between federal agencies such as the CDC, Department of Agriculture, the FDA and state health departments.

“While FoodNet continues to monitor some major foodborne pathogens,” Forster reports, “active surveillance requirements” for other pathogens including cyclospora were cut.

However, Forster cites other experts who say cuts to FoodNet likely don’t have a big effect because there’s still robust monitoring and reporting at state and local levels that kick up information to the CDC. But the same expert warns that cuts “have consequences for understanding foodborne disease trends over time.”

Read more: Unresolved Cyclospora Parasite Outbreak Raises Questions About CDC Cuts