Cyclosporiasis parasite West Virginia outbreak: Is lettuce, green salad behind the surge in 'explosive diarrhea' cases as Michigan tops 2,600 infections?

Cyclosporiasis parasite outbreak: The cyclosporiasis parasite outbreak is expanding across the United States, with Michigan reporting 2,640 cases and health officials investigating lettuce and salad greens as a possible source. At the same time, West Virginia has reported an unusual spike in infections, declaring a statewide outbreak after confirming 69 cases and eight hospitalizations, far above the state's typical annual average. Ohio has reported hundreds of cases, Kentucky has also confirmed infections and the CDC is investigating.

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The outbreak is not limited to Michigan alone in the US. Illinois has reported nearly 200 cases, including 47 probable cases in Chicago, while the Centers for Disease Control and Prevention (CDC) says 31 states have reported cyclosporiasis cases, with 86 people hospitalized so far.

Lettuce and salad greens emerge as possible source

The Michigan Department of Health and Human Services (MDHHS) said investigators have identified lettuce or salad greens as a potential source of the outbreak based on early findings.

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However, officials stressed that other food items cannot be ruled out, and there is currently no evidence pointing to a specific type of lettuce, grower or supplier.

“Although we do not have a definite product identified as the source of the outbreak, we want to let Michiganders know what we have learned so far so they can take steps to protect their families,” MDHHS Chief Medical Executive Dr. Natasha Bagdasarian was quoted as saying by NBC.

“Early information has shown lettuce as a common product that regularly comes up during the investigation. We will continue to provide updates as we learn more.”

What is the cyclosporiasis parasite?

Cyclospora is a microscopic parasite that infects the intestines and causes cyclo­sporiasis, a foodborne illness best known for causing watery or "explosive" diarrhea.

People usually become infected after eating or drinking something contaminated with the parasite. Fresh produce has been linked to several previous outbreaks because the parasite can stick to the surface of fruits and vegetables.

Although Cyclospora can be present in contaminated water, Michigan health officials say there is currently no evidence linking recreational swimming or water activities to the ongoing outbreak.

Officials noted that foodborne exposure—particularly through contaminated produce—remains the primary focus of the investigation.

What foods have been linked to the outbreak?

While lettuce and salad greens are currently under investigation, officials say the exact source has not yet been confirmed. Health authorities are advising consumers, restaurants and commercial kitchens to take extra precautions when handling leafy greens.

They recommend:

• Buy whole heads of lettuce instead of pre-washed bagged lettuce or salad kits whenever possible.
• Remove and discard the outer two to three layers of leaves.
• Thoroughly wash the remaining leaves under clean running water.
• Cook leafy greens when appropriate. Heating food to 158°F (70°C) kills the parasite.
• Wash all fresh fruits and vegetables under running water before eating.
• Peel produce with removable skins whenever possible.

Officials also note that washing alone may not completely remove Cyclospora because the parasite is resistant to routine chemical disinfection.

The Illinois Department of Public Health (IDPH) also reminded consumers: "Not everything is meant to be cooked, which is why washing your produce is still one of the best food safety habits—whether you're planning to eat it raw or cook it. Simply rinse fruits and vegetables under clean running water and scrub firm produce (like melons) with a produce brush. No soap needed."

Foods linked to previous Cyclospora outbreaks

Health officials say previous outbreaks in the U.S. and Canada have been associated with:

• Bagged salad mixes
• Fresh cilantro (coriander leaves)
• Fresh basil
• Raspberries
• Snow peas
• Green onions (scallions)

Cyclosporiasis symptoms to watch for

The illness is widely known for causing explosive diarrhea, but patients may experience several other symptoms as well.

Common symptoms include:

• Watery or explosive diarrhea
• Stomach cramps
• Bloating
• Nausea
• Loss of appetite
• Fatigue
• Occasional low-grade fever

Why this illness is different from other food poisoning

One unusual feature of cyclosporiasis is that symptoms do not appear immediately. Unlike many foodborne illnesses that develop within hours, Cyclospora infections can take up to two weeks before symptoms begin.

The illness can also last much longer than typical food poisoning.

According to the Illinois Department of Public Health: "Most people recover within 1-2 weeks with rest and fluids, though symptoms can sometimes last longer or return. Some people may need antibiotics prescribed by a healthcare provider."

What should you do if you develop symptoms?

Michigan health officials are urging anyone experiencing frequent watery diarrhea to contact a healthcare provider. They also advise patients to specifically request testing for Cyclospora, as routine stool tests may not detect the parasite.

If the infection is confirmed, treatment generally includes prescription antibiotics, along with rest and plenty of fluids to prevent dehydration.

As investigators continue tracing the source of the outbreak, health officials say practicing safe food handling and washing fresh produce remain the best ways to reduce the risk of infection.