NEW YORK (AP) — Nearly 1,000 people in Michigan have been diagnosed with a parasitic infection that can cause weeks of watery diarrhea, making it the largest such outbreak in the state’s history and one of the largest in the nation in years.
No deaths have been reported and the source of cyclospora infection has not been identified. Meanwhile, investigations into similar illnesses continue in 28 other states, including Ohio, where people just across the Michigan border are also getting sick.
Michigan officials first announced the outbreak last week when they learned of more than 170 cases — all in the southeastern part of the state — since June 22. Michigan typically sees only about 50 cases a year.
On Wednesday, the state reported number rose to 992, including about 40 hospitalizations. Just across the state line in Lucas County, Ohio, there were 306 cases reported as of Wednesday. There have been more than 500 cases in northwest Ohio.
Cyclospora outbreaks are difficult to investigate, and the sources of food poisoning are difficult to determine. But “there’s clearly an outbreak going on now that’s related to this,” Dr. Natasha Bagdasarian, Michigan’s chief medical officer, told The Associated Press on Wednesday.
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 and sometimes explosive bowel movements,” according to the U.S. Centers for Disease Control and Prevention. The disease, called cyclosporiasis, is usually not life-threatening and is usually treated with antibiotics. Flashes most often occur in late spring and summer.
The heat-loving parasite infects the intestines and spreads through feces. In the past, people became infected by eating fruit or vegetables who have been exposed to irrigation water contaminated with feces.
This disease is less common than a number of other foodborne illnesses, including salmonella and E. coli. For many years, only a few outbreaks of cyclospora were reported each year in the United States. But that number began to rise about a decade ago, with a particularly notable surge in 2018 and 2019. Experts attribute the increase to climate change and improved detection.
How is this outbreak different from previous ones in the US?
Comprehensive data on Cyclospora outbreaks is not available. But available information shows that only a small number of documented outbreaks in the past 20 years have exceeded 1,000 cases. The 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.
There are several reasons why it’s difficult to know the exact number of losses, says Melanie Firestone, a foodborne illness researcher at the University of Minnesota. Some tests used to check for types of food poisoning are not designed to detect cyclospora, “so it is vastly underreported,” she said.
Other problems: Technicians cannot grow the parasite in laboratories, making it difficult to obtain evidence from contaminated products. And it can be difficult to figure out what’s common in sick people’s foods because sometimes it’s one ingredient that can be common in multiple recipes—basil or cilantro, for example.
Additionally, it is possible that food distributors may be sending contaminated food to both grocery stores and restaurants, making it difficult to determine the origin of tainted food. Investigations can take months and sometimes never find a clear source.
What is the current situation?
Cases appear to be rising in and around southeast Michigan. But it is not considered a national health emergency.
There is no evidence that the parasite has evolved to become more infectious, said Dianna Blau, acting director of the Centers for Disease Control and Prevention’s (CDC) Division of Parasitic Diseases.
There are thousands of cases of cyclospora in the U.S. every year, and it’s unclear how unusual this year will be, she added. However, according to current national data from the CDC, the total number of cases now is four times higher than at the same time last year, which lags sharply behind what states are reporting.
Michigan appears to be suffering the most from this, but the state’s aggressiveness in investigating and reporting cases may be “one of the reasons why this appears to be a Michigan problem,” Bagdasarian said.
How to protect yourself from cyclospora?
People whose diarrhea does not go away on its own within a few days should contact their doctor and discuss the possibility of cyclospora infection, officials said.
The best way to prevent parasite infection is to avoid eating food and water that may be contaminated.
Fresh produce should be washed thoroughly before use. But keep in mind that cyclospora can actually stick to some foods, so washing may not eliminate the risk of contamination.
While Michigan officials investigate the potential source, they recommend consumers buy whole heads of lettuce rather than pre-washed, bagged lettuce or lettuce mixes, and remove the outer two to three leaves before washing the remaining leaves under running water.
They also say that vegetables should be cooked whenever possible.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. AP is solely responsible for all content.