Experts weigh in on Michigan cyclosporiasis testing as outbreak grows

As an outbreak of a parasitic gastrointestinal illness sweeps through Michigan, doctors' offices, urgent care clinics and hospital emergency departments are seeing a rise in visits from people concerned they may have cyclosporiasis.

Michigan infectious disease experts told the Detroit Free Press that it's important to keep in mind that symptoms of cyclosporiasis — watery, sometimes explosive diarrhea, gas, bloating, low-grade fever, loss of appetite and, occasionally, nausea and vomiting — can overlap with other types of foodborne illness and viral and bacterial infections.

That's why it's crucial for people to seek testing if they develop symptoms that include bouts of frequent diarrhea that stretch over several days, said Dr. Rebecca Schein, a pediatric infectious disease specialist at the University of Michigan Health-Sparrow in Lansing.

More: Michigan parasitic diarrhea cases swell to 700: How to prevent it

"A lot of things can give you an upset stomach and diarrhea for a day or two," said Schein, who also is an assistant professor of pediatric and human development in the College of Human Medicine at Michigan State University. "This does last longer than regular diarrhea. So, if you've only had diarrhea for a day or two, that's not what this is.

"If you have one episode of diarrhea, I wouldn't rush to go get tested. It's when the diarrhea persists for days and is ongoing that people ought to seek testing."

Dr. Adam Ressler, a clinical assistant professor of infectious disease and internal medicine at the University of Michigan, said people who see a doctor with concerns about cyclosporiasis shouldn't expect to leave that initial office visit with a prescription for antibiotics. Test results must come back first that show a positive result.

"Testing the stool is really important to confirm the diagnosis and make sure we know what we're treating," Ressler said.

Test results can take anywhere from one to three days to get back from the lab, Schein said. If a person tests positive for cyclosporiasis, the recommendation is to treat the infection with a particular type of antibiotic, called trimethoprim sulfamethoxazol, which is sold under such brand names as Bactrim or Septra.

For most people, cyclosporiasis "is what we call a self-limited infection," Schein said, "which means it will go away on its own eventually. So, you don't absolutely have to be treated. However, as opposed to other stomach bugs like E. coli or salmonella or shigella that last three days, five days, maybe a week, this can last ... four to six weeks and it can kind of come and go. Because it lasts so long, the general recommendation is to be treated because you'll feel better a lot sooner."

People with compromised immune systems, such as those who are on chemotherapy, transplant recipients and those who take medicine to suppress their immune systems, may be unable to rid themselves of the parasite without antibiotic treatment, Schein said.

They "typically won't get better on their own," Schein said, and will need treatment with antibiotics.

Search for a source takes time, experts say

Although local, state and federal agriculture and health workers say they are scrambling to identify a common source of almost 1,000 cyclosporiasis infections in Michigan and other clusters of cases nationally, it's difficult work, Ressler said. And they can't do that work successfully without the help of the public.

"The health department is still working on trying to figure out where this is coming from," he said. "If folks do develop symptoms ... and test positive, they are likely to be contacted by the health department."

Ressler urged people who've been infected to answer calls from unknown numbers and to cooperate with public health investigators.

"I just think it's real important that folks know that the health department's really trying to figure this out," he said. "If they're contacted by the health department, they should do their best to work with the health department to provide them whatever information they can to help them get to the bottom of this."

It's labor-intensive work tracking down each person who has been infected and getting a detailed history of what they ate before they got sick, Schein said.

The effort could be slower now than in the past because of deep cuts to federal funding since 2025 for local and state public health departments, the U.S. Centers for Disease Control and Prevention, the U.S. Food and Drug Administration as well as the U.S. Department of Agriculture and state agriculture departments.

Adding to the difficulty tracking this disease, Schein said, is that sickness can be delayed anywhere from two days to two weeks after a person eats food or drinks water contaminated with the microscopic cyclospora cayatenensis parasite. That means that public health investigators must get a detailed history of what people have eaten for at least 14 days to completely assess possible sources of the infection.

"When they do an outbreak investigation, they ask about all of the foods you've eaten, but that means you have to go back two weeks," Schein said. "Most people can't go back two days, nevertheless two weeks" in recalling their dietary history. "So, part of the issue with identifying the source could be related to people not fully remembering what they ate."

Michigan typically sees about 50 cases of cyclosporiasis every summer, Schein said, which have been linked in the past to freshwater exposure to the parasite and to contaminated food.

"That's actually also part of the problem with the numbers and why there's been a delay," she said. "The health department has to do DNA testing to figure out which are the cases that are just our local cases that we get every year versus ... the ones that are actually linked to this outbreak."

How to protect yourself from cyclosporiasis infection

While the work continues to identify a common source of the outbreak, the Michigan Department of Health and Human Services says there are things people can do to protect themselves from illness.

The best practice is to thoroughly wash all fresh produce and cook it to a temperature of at least 158 degrees before eating it, which kills the parasite.

If cooking isn't an option, the health department said, people should at least be aware of which types of produce have been associated with previous outbreaks and the best ways to clean them. Those foods include:

Bagged salad mixes and kits, such as precut lettuce blends with romaine, iceberg, red cabbage and carrots.Fresh herbs such as cilantro, basil.Raspberries.Snow peas.Green onions, also known as scallions.

The state health department also suggested that people avoid buying prewashed bagged lettuce or salad mixes during this outbreak. Instead, it recommends buying a whole head of lettuce. When preparing, people should throw away the outer two or three layers of leaves and thoroughly wash the inner leaves under running water.

If you're preparing herbs, thoroughly wash them under running water while separating the leaves.

For green onions, prep should include trimming the root end and removing the outer layer. Once that's done, wash them thoroughly under running water.

Consider using frozen raspberries, rather than fresh to reduce risk. The fruit's bumpy surface makes raspberries especially difficult to clean. The parasite can hide in its tiny crevices. Freezing may reduce the risk, but the health department warns it does not guarantee the fruit won't be contaminated.

With snow peas, be sure to rub the surface of the vegetable while cleaning it under running water.

Be sure to wash all fresh produce, even melons, cucumbers and other fruits and vegetables you plan to peel and always wash your hands with soap and water before and after handling or preparing food.

The recommendations are particularly important for infants, young children and elderly people, the state health department says, as well as anyone who is at higher risk of dehydration, and people with weakened immune systems, such as those who are taking chemotherapy or are organ transplant recipients.

Other things you can do to reduce your risk of foodborne illness:

Scrub firm fruits and vegetables, such as melons and cucumbers, with a clean produce brush.Cut away any damaged or bruised areas on fruits and vegetables before preparing and eating.Wash and sanitize utensils and surfaces before and after handling food. Wash and sanitize display cases and refrigerators where fresh produce is stored.Wash and sanitize cutting boards, surfaces and utensils used to prepare, serve or store fresh produce.Refrigerate cut, peeled or cooked fruits and vegetables as soon as possible.

Tracking the cyclosporiasis outbreak in Michigan

As of 9:30 a.m. July 8, nearly 1,000 cases of cyclosporiasis have been identified in Michigan since June 22, the state health department reported.

At least 36 people have been hospitalized, said Laina Stebbins, a spokesperson for the state health department. No deaths have been reported.

The counties with the largest number of cases — each with more than 20 — are: Monroe, Washtenaw, Lenawee, Shiawassee, Wayne, Jackson, Oakland, Ingham and Livingston, Stebbins said.

"No specific produce grower, supplier or type of produce has been identified as the source," she said. "While the investigation continues, our priority is reducing the risk of additional illnesses.

"On July 4, MDHHS issued enhanced recommendations for restaurants, commercial kitchens and other entities preparing or serving fresh produce in southeast Michigan. ... We are working closely with food service establishments and other partners to reinforce enhanced food safety practices while the investigation continues.

"We anticipate having additional information later this week and will continue to provide information as it becomes available."

This story has been updated with new information.

Contact Kristen Shamus: kshamus@freepress.com. Subscribe to the Detroit Free Press.