Health officials are working to trace the source of a widespread Cyclospora outbreak that has sickened people across 31 states, sparking concerns about whether lettuce remains safe to eat.

The parasitic infection, which affects the small intestine, has placed fast-food chain Taco Bell under scrutiny as investigators examine possible links between the restaurant’s fresh ingredients and the spike in illnesses.

According to federal and state health agencies, including the Centers for Disease Control and Prevention, the Food and Drug Administration, and the Michigan Department of Health and Human Services, no specific product or supplier has yet been identified.

Many of the reported cases share a common thread: several patients said they had eaten lettuce or salad greens before symptoms began, and many had stopped at Taco Bell locations in the days before falling ill.

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In response, Taco Bell confirmed that it has voluntarily removed certain ingredients from select restaurants out of caution while awaiting further guidance from public health authorities.

"The health and safety of our guests is our top priority," the company said in a statement. It stressed that no connection to any specific food, supplier, or restaurant has been confirmed.

Since May 1, the CDC has logged 1,645 confirmed domestic cases of Cyclospora, which is commonly contracted from contaminated food or water. The agency is also investigating more than 5,100 potential additional cases.

Although 145 people have been hospitalized, experts emphasize that cyclosporiasis is usually not life-threatening. "The biggest concern is that it can cause severe, prolonged diarrhea that may last for weeks or even longer if it's not diagnosed and treated," explained Dr. Tammy Lundstrom, chief medical officer at Trinity Health in Michigan.

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Dr. Marc Siegel, Fox News medical analyst, said the parasite has appeared most often in packaged lettuce and salad bags, though no specific brand has been identified. He advised washing lettuce and all greens thoroughly and emphasized that “the chances of acquiring it still remain extremely low.”

Registered dietitian Caroline Margolis of Lifeway Foods noted that while lettuce remains a likely culprit, “the exact source remains unknown.” She suggested choosing whole heads over prewashed salad bags, discarding outer leaves, and rinsing well before use.

Margolis also urged anyone experiencing symptoms to stay hydrated and seek care if needed, adding that recovery diets should include nutrient-rich, easy-to-digest foods and probiotics such as kefir and yogurt.

Lundstrom said it is unclear whether any particular variety of produce is responsible, though similar outbreaks have involved multiple types of fruits and vegetables. She recommended iceberg lettuce as a safer option for the moment, with thorough washing and removal of outer leaves.

Consumers who prefer to take extra care can opt for frozen or canned produce until investigators pinpoint the outbreak’s source, she added.

Both health officials and nutrition experts continue to stress that fruits and vegetables remain essential to a healthy diet. They recommend washing all produce under running water, scrubbing firm items with a clean brush, removing damaged areas, and refrigerating cut produce promptly.

Lundstrom reassured consumers that “by exercising these practical preventive steps, people can still enjoy these nutritious foods” while the investigation continues.