You might dub it “produce paranoia.” On social media, videos show people clearing out their fridges, swearing off salads and debating whether it’s safe to eat cilantro.
It’s the frantic but expected internet response to the surge in cases of a diarrhea-causing parasite that’s rapidly spreading across the US, as health officials investigate whether salad greens may be contributing to the outbreak.
As of Tuesday, the US Centers for Disease Control and Prevention had received reports of 1,645 laboratory-confirmed domestic cases of cyclosporiasis and is investigating 5,100 additional reports. Cases of the “explosive diarrhea parasite” have been reported across 34 states, with Michigan among the hardest-hit regions.
The gastrointestinal illness is caused by cyclospora, a foodborne pathogen that’s difficult to trace but has historically been linked to fresh produce such as berries and lettuce. As of yet, no specific food, brand, grower or supplier has been conclusively identified as the source of the outbreak.
That hasn’t stopped people from panicking, oversharing and making a whole lot of dark memes. With any health scare, bad advice and myths spread just as fast as the actual illness. So we turned to healthcare experts to learn the facts.
“I wouldn’t necessarily suggest that people avoid produce,” said Dr. John Openshaw, an infectious disease physician and medical epidemiologist at Stanford University. “Even though the number of people involved in the current outbreak or outbreaks seems large, overall the risk remains very low to most people.”
What is cyclosporiasis?
Cyclosporiasis is caused by cyclospora cayetanensis, a microscopic parasite transmitted through fecal matter that infects the small intestine. According to infectious disease experts at Johns Hopkins, it takes only a few microscopic Cyclospora eggs to hijack your gastrointestinal tract.
In the US, previous cyclospora outbreaks have frequently been associated with fresh produce, including bagged salad mixes, cilantro, basil, raspberries, snow peas and green onions. Any food that’s contaminated and eaten uncooked can theoretically transmit cyclospora.
Unlike some stomach illnesses, such as norovirus, cyclosporiasis is unlikely to spread directly from one person to another. After the parasite leaves an infected person’s body, it generally needs at least one to two weeks in the environment before it becomes infectious.
What are the symptoms of cyclosporiasis?
The most common symptom is watery diarrhea that can be frequent and, according to the CDC, sometimes “explosive.” Other unpleasant symptoms can include stomach cramps, nausea, loss of appetite, bloating and gas, fatigue, vomiting, and low-grade fever.
Unlike deadlier foodborne illnesses such as listeria or E. coli, cyclosporiasis isn’t usually life-threatening. The biggest risk right now during the hot summer months is dehydration. “People who are sick and are having trouble keeping hydrated should talk to a doctor,” Openshaw said.
Symptoms typically begin about one week after exposure, although they can appear anywhere from two days to two weeks or longer afterward. Dr. Timothy Henrich, professor of medicine at UCSF, said it’s typical for people to have “waxing and waning symptoms” over weeks to months. Others who are infected might have minimal or even no symptoms, he said.
Because symptoms can come and go, it’s important to get tested for cycolosporasis and talk with a doctor about treatment, which is generally well-tolerated and “may reduce the chances of further local fecal-oral spread,” Henrich said.
How high is the risk?
While cyclosporasis cases span a lot of the country, the outbreak’s highest concentration is in a small cluster of states, mostly in the Midwest. Jessica Steier, a public health scientist and CEO of Unbiased Science, said that the risk is still low outside those areas.
“That being said, until the specific source of the outbreak is identified, people outside those states who are pregnant or immunocompromised might consider erring on the side of caution,” Steier said.
The CDC says that only about 9% of people who contract the parasite require hospitalization, but the risk of severe illness and lasting complications is significantly higher for seniors, young children and others with weakened immune systems. The CDC said Tuesday that it had received no reports of deaths linked to the outbreak.
How can you reduce your risk?
So far, only lettuce and salad greens have emerged as a possible source, and the CDC says no specific brand, grower, supplier, restaurant or grocery store has been identified.
As of Tuesday, there was no nationwide recommendation to throw away lettuce. However, Michigan health officials have issued more specific guidance for lettuce during the current investigation, including buying whole heads of lettuce instead of bagged lettuce or premixed salad kits (then discarding the outer three layers of leaves) and cooking leafy greens when practical.
Though washing fresh produce might reduce your exposure to cyclospora and other foodborne contaminants, it can’t guarantee the parasite will be completely removed.
“Washing produce does not meaningfully decrease the risk of Cyclospora, and heat remains the gold standard for risk reduction,” Steier said. Cooking vegetables at an internal temperature of 158 degrees Fahrenheit or higher is the only surefire way to kill the parasite.
Experts also warn against using soap, bleach or household disinfectants on produce. Fruits and vegetables can absorb soap and detergent, which may make you sick, and the CDC says routine chemical disinfection is unlikely to kill cyclospora.
Household tools or countertop items like a UV produce washer, ultrasonic cleaner or ozone device won’t make contaminated food safe to consume, either. Steier confirmed that none of those methods has sufficient real-world evidence to support their use in killing the parasite.
What should you do if you have symptoms?
Experts advise contacting a healthcare provider if you develop persistent watery diarrhea, especially if it is severe, lasts longer than a week, or goes away and then returns. Drinking fluids is also important because prolonged diarrhea can cause dehydration.
Diagnosing cyclospora requires special lab testing, and the parasite isn’t included in routine stool testing. The CDC says patients sometimes need to provide multiple samples because cyclospora can be difficult to detect.
The standard treatment is the prescription antibiotic combination trimethoprim-sulfamethoxazole, commonly sold under the brand names Bactrim and Septra. People who are allergic to sulfa drugs should discuss other options with a medical professional.
When will we know the source of the outbreak?
It may take weeks or longer to identify the source of the outbreak because investigators have to interview people with the parasite, compare what they ate and then trace foods back through the supply chain. For cyclospora, that process is especially difficult because symptoms often begin days after exposure, and people may not remember exactly what they ate.
Public health agencies have also faced staffing cuts and funding reductions in recent years, making it harder to identify outbreaks quickly and to tell people which foods to avoid. A recent study found that states with more CDC support reported more outbreaks than those without those programs, suggesting that federal funding improves detection and management.
“Tracing any outbreak like this requires trained staff and resources — any cut to those elements of a public health response would impede efforts to trace an outbreak to a specific food item and identify how a pathogen like cyclospora got into the food supply,” Openshaw said.
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