The U.S. Centers for Disease Control says it has received reports of 145 cases of cyclosporiasis acquired in the United States of people who became sick this year.

Florida's case count also rose with statistics updated overnight.

However, the Associated Press reported Wednesday that 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 state history and one of the nation’s largest in years.

No deaths have been reported and the source of the cyclospora infections hasn’t been identified. Meanwhile, investigations into similar illnesses have been going on in 28 other states, including in Ohio, where people just across the Michigan border are also becoming sick.

The Florida Department of Health updated statistics Thursday reported there are now 60 cases in Florida for the year — including 11 in Lee, 2 in Collier and 1 in Highlands counties — and cases in 25 other Florida counties and in 16 other states. There have been at least 20 hospitalizations and no deaths, the CDC said.

Michigan officials first announced the outbreak last week, when they were aware of more than 170 cases — all in the southeastern corner of the state — since June 22. Michigan usually identifies only about 50 cases each year.

Cases seem to be surging in and around southeastern Michigan. But it’s not considered a national health emergency.

On Wednesday, the state reported the number had grown to 992, including about 40 hospitalizations. Just across the state line, Lucas County, Ohio, reported 306 cases as of Wednesday. Northwest Ohio has seen more than 500 cases.

Cyclospora surges can be tricky to investigate, and food poisoning sources can be hard to establish. But “there is clearly a linked outbreak happening right now,” Dr. Natasha Bagdasarian, Michigan’s chief medical executive, told The Associated Press on Wednesday.

Cyclosporiasis is caused by several species of the microscopic parasite Cyclospora. Those infected became sick after eating food possibly contaminated by the parasite.

The CDC says investigations to identify potential sources of illness are ongoing.

Symptoms may include watery diarrhea, loss of appetite, weight loss, cramping and bloating.

The CDC said cyclospora infection is transmitted by ingesting food or water that has been contaminated with Cyclospora oocysts. Foodborne outbreaks of cyclosporiasis in the United States have been linked to consumption of fresh produce.

How does this outbreak compare to previous ones in the US?

Comprehensive data on cyclospora outbreaks is lacking. But available information shows only a small number of documented outbreaks in the last 20 years have surpassed 1,000 cases. That short list includes a 1997 outbreak tied to Guatemalan raspberries that sickened more than 1,000 in the U.S. and Canada, and a 2019 outbreak linked to Mexican basil that sickened more than 2,400.

There are several reasons it’s challenging to know the exact toll, said Melanie Firestone, a University of Minnesota foodborne illness researcher. Some tests used to check for types of food poisoning are not geared to detect cyclospora, “so there is a lot of underreporting when it comes to this,” she said.

Other challenges: Technicians aren’t able to grow the parasite in labs, making it hard to draw evidence from contaminated produce. And it can be hard to figure out what food sick people had in common, because sometimes it’s a single ingredient that might be common in multiple recipes — like basil or cilantro.

Also, it’s possible that food distributors may channel contaminated foods to both grocery stores and restaurants, making it hard to discern where tainted food came from. Investigations can take months and sometimes never find a clear source.

Geographic distribution

Cyclosporiasis occurs in many countries, but it is most common in tropical and subtropical regions. In areas where researchers have studied cyclosporiasis, the risk of infection is seasonal. However, researchers have not identified a consistent pattern regarding the time of year or the environmental conditions that might affect seasonality, such as temperature and rainfall.

United States

In the US, foodborne outbreaks of cyclosporiasis have been linked to different types of imported fresh produce, including

• Basil
• Cilantro
• Mesclun lettuce
• Raspberries
• Snow peas

To date, no outbreaks have been linked to commercially frozen or canned produce.

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