Michigan’s cyclosporiasis outbreak continues to grow, with state health officials confirming Tuesday that the statewide case count has climbed to 9,680, a jump of more than 400 cases in a single day. The Michigan Department of Health and Human Services said the tally rose from 9,253 reported cases on Monday, and that 160 people have been hospitalized since the outbreak began in late June.
State officials cautioned that the sudden increase between Monday and Tuesday does not necessarily reflect a fresh wave of new infections. Roughly 475 of the newly added cases had already occurred but were only recently logged into the system because of delays in laboratory reporting, according to health department officials. Even so, the overall trajectory of the outbreak remains upward, and cyclosporiasis has now become one of the largest foodborne illness events in the state in recent memory.
Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis, which infects the small intestine after being ingested, often through contaminated food or water. People who contract cyclosporiasis typically experience watery diarrhea, sometimes frequent and explosive, along with fatigue, nausea, cramping and a loss of appetite. Left untreated, the illness can persist for weeks and, in some cases, symptoms can return after initially subsiding. The incubation period is usually about a week, though it can range from two days to more than two weeks, which makes pinpointing an exact source of infection difficult for investigators.
Federal health officials have said the outbreak is not confined to Michigan. The Centers for Disease Control and Prevention has identified cyclosporiasis cases connected to the outbreak in dozens of states nationwide, and it expects the number of illnesses to keep climbing through the end of August, which typically marks the close of the Cyclospora season in the United States.
Investigators have not yet pinpointed the definitive source of the contamination, though state and local health departments say leafy greens, particularly lettuce and pre-packaged salad kits, remain a leading suspect given past outbreaks tied to similar products. Earlier in the investigation, a lettuce sample linked to Taylor Farms initially tested positive for the parasite, but the Food and Drug Administration later confirmed that result was a false positive, leaving the true origin of the current cyclosporiasis outbreak unresolved.
In the meantime, health officials are urging residents to take precautions with produce. Recommendations include buying whole heads of lettuce rather than pre-washed or bagged greens, discarding the outer two or three layers of leaves, and thoroughly rinsing the remaining leaves under clean running water. Because the parasite is resistant to routine washing and chemical disinfection, officials say cooking greens to at least 158 degrees Fahrenheit, when possible, is the safest way to eliminate risk. Other produce items historically linked to Cyclospora outbreaks include fresh cilantro, basil, raspberries, snow peas and green onions, all of which officials say should be washed carefully or cooked whenever feasible.
Health officials noted that people who are more vulnerable to complications from cyclosporiasis, including those undergoing chemotherapy, organ transplant recipients, young children and older adults, should be especially diligent with food safety practices. Anyone experiencing persistent gastrointestinal symptoms is being urged to contact a health care provider and notify their local health department, since testing a stool sample is the standard way to confirm a cyclosporiasis diagnosis.
As case numbers continue to rise, Michigan health officials say they are working alongside federal investigators to trace the outbreak to its source. Until then, they say basic food safety habits, including washing hands, sanitizing kitchen surfaces and properly storing produce, remain the best defense against further spread of cyclosporiasis across the state.
