Michigan health officials are investigating a growing outbreak of cyclosporiasis that has sickened 2,640 people, with early evidence pointing to lettuce or salad greens as a possible source.
The Michigan Department of Health and Human Services said Monday (July 13) that while the investigation is ongoing, no specific type of lettuce, grower, or supplier has been identified.
Other food items also have not been ruled out.
“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,” said Dr. Natasha Bagdasarian, the department’s chief medical executive. “Early information has shown lettuce as a common product that regularly comes up during the investigation.”
What is Cyclospora?
Cyclospora is a parasite that infects the intestines and can cause watery diarrhea, nausea, and stomach cramps.
The illness is typically spread by consuming food or water contaminated with the parasite.
Michigan usually reports only 40 to 50 cases of cyclosporiasis each year, making the current outbreak unusually large.
What investigators know
State health officials said they have completed more than 1,000 interviews with infected individuals while working with local, state, and federal partners to trace the source of the outbreak.
“We really need that kind of coordination to happen at the national level,” Bagdasarian said. “As soon as other states get their numbers to the CDC, we hope they can take a broader look to see whether these outbreaks are related.”
Because symptoms can take up to two weeks to develop after exposure and food distribution networks are complex, officials said the investigation could take time.
Officials emphasized there is no evidence linking the outbreak to swimming or other recreational water activities. Instead, investigators continue to focus on contaminated produce as the likely source.
Previous cyclospora outbreaks in the United States and Canada have been linked to bagged salad mixes, fresh cilantro, basil, raspberries, snow peas, and green onions.
Health officials said the investigation has been complicated by cyclospora’s long incubation period, with symptoms often taking up to two weeks to develop after exposure.
“That means investigators have to ask people about foods they ate, restaurants they visited, and grocery purchases from two to six weeks earlier,” Bagdasarian said.
How to protect yourself
As a precaution, the department is urging residents, restaurants and commercial kitchens in affected counties to take extra care when handling lettuce and salad greens.
Health officials recommend purchasing whole heads of lettuce instead of bagged, pre-washed lettuce or salad kits, discarding the outer two to three leaves before preparation and thoroughly washing the remaining leaves under clean running water.
When possible, greens should be cooked to at least 158 degrees Fahrenheit (70 degrees Celsius), which kills the parasite.
The department also recommends washing all fresh produce under running water and peeling fruits and vegetables when possible.
People at higher risk of severe illness or dehydration, including older adults, young children, organ transplant recipients and people undergoing chemotherapy, are encouraged to take extra precautions.
“Produce may have been grown on the other side of the country, possibly even in other countries, then processed somewhere else before coming into Michigan,” Bagdasarian said. “Many suppliers also distribute produce to multiple grocery stores and restaurant chains, making it harder to pinpoint the source.”
When to seek medical care
Anyone experiencing frequent watery diarrhea should contact a health care provider and specifically request testing for cyclospora, as routine stool tests may not detect the parasite.
The illness is typically treated with antibiotics, along with rest and fluids to prevent dehydration.
The Michigan Department of Health and Human Services said it will continue providing updates as the investigation progresses.