What you need to know about the cyclosporiasis outbreak

A foodborne parasitic infection has health officials urging people and restaurants to take special care with food safety.

Watch for tips in the video player above.

Health officials have not identified a source for the latest outbreak of Cyclosporiasis, caused by the parasite cyclospora cayetanensis. Michigan is at the center of the latest outbreak, reporting more than 1,500 cases as of July 10, and neighboring Ohio has hundreds more. But more than two dozen other states also have active investigations into illnesses, according to the Centers for Disease Control and Prevention.

While the illness is not fatal, symptoms are unpleasant, including bouts of explosive diarrhea that can last from days to a month.

Here's what to know.

What is cyclosporiasis?

Cyclospora cayetanensis oocysts seen under a microscope. Photo by CDC via AP

Cyclosporiasis is an intestinal illness caused by the cyclospora cayetanensis parasite. It is not fatal, and not everyone who gets cyclosporiasis will have symptoms.

But those who do may experience bouts of frequent and explosive diarrhea that could last from a few days to more than a month, along with nausea, fatigue and bloating.

How does this parasite spread?

Cyclospora is transmitted through consumption of food or water that is contaminated with feces.

You can treat an infection with antibiotics, but most people can recover without medical intervention, although it will take longer.

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Health officials haven't identified a specific source for these outbreaks. Direct person-to-person transmission is unlikely.

Cyclospora can be hard to track, as the parasite can't be reproduced in a lab, and some food poisoning tests don't detect it.

Complicating the investigation of this outbreak: in 2025, the Centers for Disease Control and Prevention made state reporting of cyclospora optional when it scaled back its Foodborne Diseases Active Surveillance Network.

How can you avoid this infection?

The CDC has two major tips.

First, avoid consuming food or water that may be contaminated with feces.

And second, follow food safety recommendations for safe preparation and storage, like cutting away damaged or bruised areas of produce.

While a specific source is unknown, health officials are warning residents and restaurants in cyclosporiasis hotspots to also do the following:

• Buy whole heads of lettuce — not pre-washed bags.
• Separate and wash all cilantro and basil leaves.
• Trim the root end and peel the outer layer of green onions.
• Gently rub snow peas and other vegetables with your hands or brush as you wash them.
• Consider avoiding fresh fruits like raspberries with exteriors that are harder to wash.

The only sure-fire way to avoid it: cooking vegetables. Cyclospora die at 158 degrees Fahrenheit.