LANSING, Mich. — The state of Michigan is working to identify the cause of a "sudden and large" increase in an infection that causes gastrointestinal issues.

State health officials have identified 174 cases of cyclosporiasis across southern Michigan since June 22. Typically, the state averages about 50 such cases a year.

The cases have chiefly been found in Monroe, Washtenaw, Wayne, Livingston, Shiawassee, Lenawee and Jackson counties, according to Lynn Sutfin, a spokesperson for the Michigan Department of Health and Human Services.

The source or sources of the infection, caused by the parasite Cyclospora cayetanensis, are not yet known, Sutfin said.

"Individuals concerned about sudden gastrointestinal illness should contact a health care provider," Sutfin said. "Cyclospora infections can be treated with antibiotics and individuals experiencing diarrheal illness or vomiting are encouraged to hydrate, particularly during the high temperatures expected this week."

The parasite, according to the department, is usually found in developing countries and spread by water or food contaminated by feces.

"In recent years, outbreaks have occurred in the U.S. as a result of eating contaminated fresh produce, especially during the summer months," Sutfin said.

Symptoms can appear within two days to two weeks after infection, according to the Centers for Disease Control and Prevention. The infection can cause "watery diarrhea with frequent and sometimes explosive bowel movements" and, without antibiotics, may last from a few days to more than a month, the CDC said.

Person-to-person transmission is unlikely, according to the CDC, and risks can be decreased by safely preparing food and avoiding contaminated food or water.

The sudden increase in infections — the number jumped from 150-plus Tuesday to more than 170 Wednesday — comes amid five years of lower instances of the illness in Michigan.

Michigan reported 56 such cases in 2022, 43 in 2023, 41 in 2024 and 54 in 2025, according the Michigan Disease Surveillance System's most recent weekly disease report.

The 174 cases reported in Michigan between June 22 and June 30 include 70 in Monroe County, 33 in Lenawee, 21 in Washtenaw, 12 in Wayne, seven in Jackson, seven in Shiawassee and 24 cases in 11 other counties and the city of Detroit, according to MDHHS.

Cases have affected individuals ranging from 8 to 84 years of age, with the median age of 41, the state health department said.

As of June 16, the CDC said it had received reports of roughly 145 cases of cyclosporiasis across 17 states since May 1. Twenty of those cases resulted in hospitalization, the agency said.

Just south of the Michigan-Ohio border, the Toledo-Lucas County Health Department also reported Tuesday a recent increase in the intestinal illness, according to WTOL-TV, Toledo's CBS affiliate. The area is just south of Monroe and Lenawee counties, where cyclosporiasis also has been identified.

----------

©2026 www.detroitnews.com. Visit at detroitnews.com. Distributed by Tribune Content Agency, LLC.