A dangerous parasite that causes explosive diarrhea is spreading across the Midwest, and federal health officials are investigating the yet-to-be-determined source of the outbreak.
Michigan, the state with the highest number of infections, recorded 1,251 cases of cyclosporiasis on Thursday, a 26% increase from the previous day. Infections are concentrated in the southeastern region of the state. Neighboring Ohio has reported more than 360 cases, according to a health department spokesman.
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Rates are also rising in other states, including New York and Illinois. Since May 1, New York City has recorded 273 cases of infection. The health department is investigating the source of exposure.
“When you hear over 1,000 cases, we’re probably talking about many more people who haven’t been diagnosed,” said Daniel Griffin, an infectious disease physician and president of the nonprofit Parasites Without Borders.
According to the Centers for Disease Control and Prevention, the disease may cause frequent watery diarrhea for days or even months. It results from eating a tiny parasite called Cyclospora that contaminates food or water. Outbreaks in the United States are often linked to basil, cilantro, lettuce and raspberries, or originate from infections abroad.
“It really can be this explosive, severe diarrhea that doesn’t get better,” Griffin said, noting that it can happen even in healthy people.
Michigan typically sees about 50 cases per year. Doctors say the surge in cases since June 22 has a common source. The CDC is working with the U.S. Food and Drug Administration to find the origin and help contain the outbreak.
Taco Bell franchisees have stopped serving lettuce at some stores in Michigan as a precaution against an outbreak, according to a person familiar with the matter who was not authorized to speak publicly. The state’s health department earlier issued guidance to curb the spread of the outbreak and recommended special handling of lettuce and other leafy greens, including extra washing and cooking.
A Taco Bell spokesman declined to comment.
Restaurant Brands International Inc., the parent company of chains including Burger King and Popeyes, and Inspire Brands Inc., owner of restaurants including Dunkin’ and Jimmy John’s, said they have not been affected by the outbreak. Wendy’s said it was not aware of any impact on its supply chain or restaurant operations. Chains including Chipotle Mexican Grill Inc. and Chick-fil-A Inc. did not respond to requests for comment.
The parasite is usually spread from person to person in a fairly indirect way, Griffin said. For example, people who are infected with Cyclospora or who have recently had diarrhea due to Cyclospora may contaminate food and spread the pathogen when they eat it.
Without an identified source, “people don’t know what to avoid,” said Bobbi Pritt, a pathologist and clinical microbiologist at the Mayo Clinic. “We eat a lot of fresh produce this time of year.”
Lynn Sutphin, a spokesperson for the Michigan Department of Health and Human Services, said once someone tests positive, local health departments conduct interviews to learn more about the duration and type of their symptoms. Investigators asked the person what restaurants and grocery stores he visited, looking for specific dates, locations and items purchased.
She said the information will be shared with state and federal experts to understand the situation nationwide and help determine next steps.
The CDC has not provided an update on the national outbreak since June 16, when it said there were 145 cases in 17 states. On July 1, the Atlanta-based public health agency said there was no evidence of a single or multi-state outbreak.
Doctors say this grossly underestimates the national situation. To detect this disease, doctors need to perform special laboratory tests, but this is not always done routinely.
“I think it’s pretty safe to say that in all outbreaks, the reported numbers for any given disease are always just the tip of the iceberg,” Pritt said.
According to the CDC, the illness may last from a few days to more than a month if not treated with antibiotics. Symptoms such as loss of appetite, weight loss, nausea, and stomach cramps may come and go.
Griffin said people should seek medical care if gastrointestinal problems persist for more than a few days and should continue to stay hydrated if symptoms develop. Young children and the elderly are most likely to require hospitalization.
The CDC says the best way to prevent infection is to avoid food and water that may be contaminated with feces and to be careful when handling produce.
