A parasite that causes diarrhea is spreading. Should you stop eating salad?

You might call it “producing paranoia.” Videos on social media show people emptying their refrigerators, giving up salads and wondering if it’s safe to eat cilantro.

It’s the internet’s frantic but expected response to rising cases of a diarrhea-causing parasite that is spreading rapidly across the United States, as health officials investigate what type of product is contributing to the outbreak.

The gastrointestinal illness is caused by cyclospora, a foodborne pathogen that is difficult to trace but historically associated with fresh produce such as berries and lettuce. For several weeks, no specific food, brand, producer or supplier was conclusively identified as the cause of the outbreak, leading to panic and numerous dark memes.

The CDC reported Thursday evening that officials were investigating a link to shredded iceberg lettuce served at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio and West Virginia. The agency advised consumers to avoid eating shredded lettuce from Taco Bell stores in those states. The CDC said Taco Bell was working to remove contaminated products from its locations and was also working with the supplier to determine whether any had been sent to other locations.

Earlier this week, the U.S. Centers for Disease Control and Prevention had received reports of 1,645 domestic laboratory-confirmed cases of cyclosporiasis and was investigating 5,100 additional reports. Cases of the “explosive diarrhea parasite” have been reported in 34 states, with Michigan being one of the hardest hit areas.

When it comes to health problems, bad advice and myths spread as quickly as the disease itself. So we turned to healthcare experts for the facts.

“I wouldn’t necessarily suggest people avoid the products,” 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(s) appears large, the overall risk remains very low for most people.”

What is cyclosporosis?

Cyclosporiasis is caused by cyclospora cayetanensis, a microscopic parasite transmitted through feces that infects the small intestine. According to infectious disease experts at Johns Hopkins, all it takes is a few microscopic cyclospora eggs to hijack your gastrointestinal tract.

In the United States, previous Cyclospora outbreaks have often been associated with fresh produce, including packaged salad mixes, cilantro, basil, raspberries, snow peas, and green onions. Any contaminated food eaten raw can theoretically transmit cyclospora.

Unlike some stomach illnesses, such as norovirus, cyclosporosis is unlikely to spread directly from person to person. Once the parasite leaves an infected person’s body, it usually takes at least one to two weeks in the environment before it becomes infectious.

What are the symptoms of cyclosporosis?

The most common symptom is watery diarrhea which can be frequent and, according to the CDC, sometimes “explosive.” Other unpleasant symptoms may include stomach cramps, nausea, loss of appetite, bloating and gas, fatigue, vomiting and mild fever.

Unlike more deadly foodborne illnesses such as listeria or E. coli, cyclosporosis is generally not life-threatening. The biggest risk currently during the hot summer months is dehydration. “People who are sick and have trouble staying hydrated should talk to a doctor,” Openshaw said.

Symptoms usually begin about a week after exposure, although they can appear anywhere from two days to two weeks or more afterward. Dr. Timothy Henrich, a professor of medicine at UCSF, said it’s common for people to experience “waxing and waning symptoms” over weeks or even months. Other infected people may have minimal or no symptoms, he said.

Because symptoms can come and go, it’s important to get tested for cyclosporase and talk with a doctor about treatment, which is generally well tolerated and “may reduce the chances of local fecal-oral spread,” Henrich said.

What is the risk?

Although cyclosporosis cases cover much of the country, the greatest concentration of the epidemic is in a small group of states, primarily in the Midwest. Jessica Steier, a public health scientist and CEO of Unbiased Science, said the risk remains low outside of these areas, but anyone who is “pregnant or immunocompromised might consider exercising caution.”

The CDC says only about 9% of people who contract the parasite need to be hospitalized, but the risk of severe illness and lasting complications is significantly higher for older adults, young children and others with weakened immune systems. The CDC said Tuesday it had not received any reports of deaths linked to the outbreak.

How can you reduce your risk?

As of Tuesday, there was no national recommendation to throw out lettuce. However, Michigan health officials have issued more specific guidelines for lettuce during the ongoing investigation, including purchasing 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 possible.

Although washing fresh produce can reduce your exposure to cyclospora and other foodborne contaminants, it cannot guarantee that the parasite will be completely eliminated.

“Washing produce does not significantly decrease the risk of cyclospora, and heat remains the gold standard for risk reduction,” Steier said. Cooking vegetables to 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 products. Fruits and vegetables can absorb soap and detergent, which can make you sick, and the CDC says routine chemical disinfection is unlikely to kill cyclospora.

Household tools or countertop items like a UV washer, ultrasonic cleaner, or ozone device will also not make contaminated food safe for consumption. Steier confirmed that none of these methods have enough concrete evidence to support their use in killing the parasite.

What to do if you have symptoms?

Experts advise contacting a healthcare professional if you develop persistent watery diarrhea, especially if it is severe, lasts more than a week, or goes away and then returns. Drinking fluids is also important because prolonged diarrhea can cause dehydration.

Diagnosis of cyclospora requires special laboratory tests and the parasite is not included in routine stool tests. 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 with allergies to sulfa drugs should discuss other options with a healthcare professional.

Why is it so difficult to identify the source of an outbreak?

It often takes weeks or longer to identify the source of a parasitic outbreak, as investigators must compare what sufferers ate and then trace the foods through the supply chain. For cyclospora, this process is particularly difficult because symptoms often begin within days of exposure.

Public health agencies have also faced staffing and funding cuts in recent years, making it harder to quickly identify outbreaks and advise which foods to avoid. A recent study found that states with greater CDC support reported more outbreaks than those without these programs, suggesting that federal funding improves detection and management.

“Tracking an outbreak like this requires trained staff and resources. Any reduction in these elements of a public health response would hamper efforts to trace an outbreak to a specific food and identify how a pathogen like cyclospora entered the food supply,” Openshaw said.