Michigan Cyclospora Outbreak Surpasses 1500 Cases as Investigation Continues

A recent outbreak of cyclospora, a parasitic infection that causes watery diarrhea, has plagued more than 1500 people in Michigan, according to federal and state surveillance.^1-3

This is the largest cyclospora emergence in the state and one of the largest nationwide. Michigan health officials first alerted the public after identifying 170 confirmed cases.¹ The CDC’s most recent surveillance report documented 843 cases acquired in the US and 86 hospitalizations nationwide.² State-level reporting is often timelier when compared with federal reports. Hence, Michigan’s state health department reporting 1562 confirmed cases and 44 hospitalizations as of July 10 is a significant jump from 992 confirmed cases and approximately 40 hospitalizations only 2 days ago on Wednesday, July 8.^1,3 Separately, the CDC tracks cases tied to travel outside the US. As of July 9, the agency reported 343 such cases nationwide, spanning 32 states—a distinct count from Michigan's outbreak total.²

Although the initial outbreak appeared to be localized to the southeastern corner of the state—which has about 50 cases of cyclospora per year—similar illnesses are under investigation in 28 other states.¹

What Is Cyclospora and How Does It Spread?

Cyclosporiasis is a foodborne intestinal parasitic infection caused by the Cyclospora cayetanensis parasite that can cause frequent and potentially profuse watery diarrhea. Symptoms typically begin about 1 week after exposure; however, it can range anywhere from 2 days to 2 weeks or more. It is not life-threatening, but people can experience a range of symptoms lasting a couple of days to over a month without treatment, and some may not experience any at all.²

Standard treatment for infection is trimethoprim-sulfamethoxazole. Although many otherwise healthy immunocompetent individuals can eventually recover without antimicrobial treatment, symptoms may persist for weeks.²

The parasite spreads through consumption of fruits or vegetables exposed to feces-contaminated irrigation water. However, Michigan state health officials are currently investigating the source of the outbreak and have not reported any findings yet. But “there is clearly a linked outbreak happening right now,” Dr. Natasha Bagdasarian, Michigan’s chief medical executive, told The Associated Press on Wednesday.¹

The unusually high flare of infections has crossed borders as Lucas County, Ohio, reported more than 300 cases on Wednesday.¹ Since cyclospora is not known to spread from direct person-to-person contact, investigators suspect a possible contaminated food or water source in the area, although no source has been confirmed.²

CDC, Michigan Officials Continue Investigating the Outbreak Source

The CDC, in tandem with local, state, and federal public health authorities, is working diligently to collect and report its findings and to investigate several cases across multiple states.²

While this outbreak is not quite out of the ordinary, with confirmed cases rising every year in the late spring and summer, health officials say this year’s scale is unusual, and it is recommended to take cautionary actions to prevent infection.²

The CDC recommends avoiding food or water that may be contaminated with feces and following food safety recommendations for preparation and storage.

These include buying whole heads of lettuce as opposed to pre-washed bags; separating and washing cilantro and basil leaves; trimming the root and peeling the outer layer of green onions; brushing other vegetables as you wash them; and avoiding fresh fruits with difficult-to-wash exteriors.⁴

The American Journal of Managed Care^® will continue to report on this outbreak as new data becomes available.

References

1. Stobbe M. Outbreak of diarrhea-causing parasite grows to more than 1,000 cases. AP News. July 9, 2026. Accessed July 10, 2026. https://apnews.com/article/cyclospora-outbreak-michigan-31e5e0034d39e85c844065a2bd593ecb

2. Surveillance of cyclosporiasis. Centers for Disease Control and Prevention. July 10, 2026. Accessed July 10, 2026. https://www.cdc.gov/cyclosporiasis/php/surveillance/index.html

3. Infectious disease outbreaks. Michigan Department of Health and Human Services. July 10, 2026. Accessed July 10, 2026. https://www.michigan.gov/mdhhs/keep-mi-healthy/infectious-diseases/infectious-disease-outbreaks

4. McPhillips T. What you need to know about the cyclosporiasis outbreak. PBS News. July 10, 2026. Accessed July 10, 2026. https://www.pbs.org/newshour/health/what-you-need-to-know-about-the-cyclosporiasis-outbreak