Michigan health officials warn that lettuce or salad greens could be one of the prime sources of infection of the deadly cyclosporiasis infection that’s plaguing the country.

So far, there have been 2,640 reported cases in Michigan of the foodborne illness according to NBC News — a huge percentage of the total of nearly 3,000 cases of the gastrointestinal illness that’s shown up in 31 states. The Centers for Disease Control and Prevention say that 86 people have been hospitalized.

“Early information has shown lettuce as a common product that regularly comes up during the investigation,” Dr. Natasha Bagdasarian, the state’s chief medical executive, said in a statement.

Officials stress that the investigation is still unfolding and that no single farm, supplier, brand, or specific type of lettuce has been identified. The Michigan Department of Health and Human Services says early interviews with more than 1,000 infected people repeatedly turned up lettuce or salad greens, but investigators have not ruled out other foods as possible sources.

Cyclosporiasis is caused by the microscopic parasite Cyclospora cayetanensis. People usually become sick after eating food or drinking water contaminated with the parasite. Symptoms often begin about a week after exposure, although they can appear anywhere from two days to two weeks later. The illness can cause prolonged watery diarrhea, stomach cramps, nausea, fatigue, loss of appetite, bloating, gas, and sometimes body aches or low-grade fever.

Health officials say the illness is rarely fatal, but it can be miserable and long-lasting. Untreated symptoms may ease and return over several weeks, and dehydration can become a concern, especially for older adults, young children, and people with weakened immune systems. Doctors can diagnose cyclosporiasis through stool testing, and the infection is commonly treated with the antibiotic trimethoprim-sulfamethoxazole, along with fluids to prevent dehydration.

TAKE PRECAUTIONS

Because Cyclospora has been linked in past outbreaks to fresh produce that is eaten raw, Michigan officials are urging consumers in affected areas to take extra care with lettuce and leafy greens. They recommend buying whole heads of lettuce rather than prewashed bagged lettuce or premixed salad kits, discarding the outer two or three layers of leaves, and washing the remaining inner leaves thoroughly under running water.

For greens that can be cooked, cooking is considered the safest option. Routine rinsing and chemical sanitizers may reduce risk but cannot guarantee removal of the parasite. The Centers for Disease Control and Prevention also advises that consumers wash their hands before and after preparing produce, scrubbing firm fruits and vegetables with a clean brush, cutting away bruised or damaged areas, and refrigerating cut, peeled, or cooked produce within two hours.

Consumers who develop persistent watery diarrhea after eating fresh produce should contact a healthcare provider, especially if symptoms last more than a few days or include signs of dehydration such as dizziness, reduced urination, or extreme weakness. Health departments are asking confirmed patients to cooperate with food-history interviews because those details can help investigators trace the outbreak through complex distribution networks.