NEW YORK — Nearly 1,000 people in Michigan have been diagnosed with a parasitic infection that can cause weeks of watery diarrhea, the largest such outbreak in the state’s history and one of the largest in the country in years.
No deaths have been reported and the source of Cyclospora infection has not been identified. Meanwhile, investigations into similar illnesses are underway in 28 other states, including Ohio, and people across the border in Michigan have also become ill.
Michigan officials first announced the outbreak last week after learning of more than 170 cases since June 22, all in the southeastern part of the state. Michigan typically only sees about 50 cases each year.
On Wednesday, the state reported that number had increased to 992 people, about 40 of whom were hospitalized. Across the state line, Lucas County, Ohio, reported 306 cases as of Wednesday. More than 500 cases have been confirmed in northwest Ohio.
Cyclospora outbreaks are difficult to investigate and can make it difficult to determine the cause of food poisoning. But Michigan’s medical director, Dr. Natasha Baghdasaryan, told The Associated Press on Wednesday that “there is clearly a related outbreak going on right now.”
Here’s what you need to know about the current situation.
What is Cyclospora?
Cyclospora is a microscopic, spherical parasite that typically causes watery diarrhea “with frequent, sometimes explosive defecation,” according to the Centers for Disease Control and Prevention. This disease, called cyclosporiasis, is usually not life-threatening and is usually treated with antibiotics. Outbreaks tend to occur most often in late spring and summer.
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This heat-loving parasite infects the intestines and spreads through feces. In the past, some people have been infected by consuming fruits and vegetables that have been exposed to irrigation water contaminated with feces.
It is less common than many other types of food poisoning, such as salmonella and E. coli. For many years, very few Cyclospora outbreaks were reported each year in the United States. However, that number started increasing about a decade ago, with a particularly notable spike in 2018 and 2019. Experts attribute the increase to climate change and improved detection.
How does this outbreak compare to previous outbreaks in the United States?
Comprehensive data on the occurrence of Cyclospora are lacking. However, available information indicates that only a small number of outbreaks recorded over the past 20 years have exceeded 1,000 cases. That short list includes a 1997 outbreak linked to Guatemalan raspberries that sickened more than 1,000 people in the United States and Canada, and a 2019 outbreak linked to Mexican basil that sickened more than 2,400 people.
Melanie Firestone, a food poisoning researcher at the University of Minnesota, said there are several reasons why it’s difficult to know the exact number of deaths. Some tests used to determine the type of food poisoning are not designed to detect Cyclospora. “So there’s a lot of underreporting on this,” she says.
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Other challenges: Technologists can’t grow parasites in the lab, making it difficult to extract evidence from contaminated produce. It can also be a single ingredient that is common to multiple recipes, such as basil or cilantro, so it can be difficult to understand what is common for people with food poisoning.
Additionally, food distributors may distribute contaminated food to both grocery stores and restaurants, making it difficult to determine where the contaminated food came from. Investigations can take months, and clear sources may not be found.
What is the current situation?
Cases appear to be surging in and around southeastern Michigan. However, this is not considered a national health emergency.
Deanna Blau, acting director of the CDC’s parasitic diseases branch, said there is no evidence that the parasite has evolved to be more infectious.
Thousands of cases of Cyclospora disease are reported in the United States each year, but it’s not yet clear how unusual this year is, she added. Still, current national data from the CDC shows the number of cases so far is four times higher than at the same time last year, and far behind what states are reporting.
Michigan appears to be the worst affected, but the state’s aggressiveness in investigating and reporting incidents “may be part of the reason this seems to be a problem in Michigan,” Baghdasarian said.
How can I protect myself from Cyclospora?
People with diarrhea that doesn’t go away on its own after a few days should talk to their health care provider to discuss the possibility of hyalosporosis, officials said.
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The best way to prevent infection with parasites is to avoid food and water that may be contaminated.
Wash fresh food thoroughly before eating. However, keep in mind that Cyclospora can actually stick to some foods, so washing them may not eliminate the risk of infection.
As Michigan officials investigate potential sources, they recommend consumers buy whole lettuce rather than pre-washed, bagged lettuce or salad mixes, and remove the outer two to three leaves before washing remaining leaves under running water.
People are also told to cook vegetables if possible.
— Mike Stobbe
