Michigan reported 3,309 cyclosporiasis cases, a 25% increase from the 2,640 counted one day earlier, as state health officials focused part of their investigation on lettuce and salad greens. The illnesses had been detected since late June and were concentrated mainly in southeastern Michigan.
The Michigan Department of Health and Human Services said 44 people had been hospitalized as of July 9. Cases had been found in 56 counties, including some in the northern Lower Peninsula and Upper Peninsula. Listed local totals included at least 339 in Wayne County, 290 in Washtenaw County and 258 in Monroe County as of July 13.
Cyclosporiasis is caused by Cyclospora cayetanensis, a parasite associated with diarrhoea and abdominal cramping. State chief medical executive Dr. Natasha Bagdasarian said early information repeatedly identified lettuce in patient histories, but emphasized that investigators did not yet have a definitive product. Other foods could not be completely excluded, and no grower or supplier had been named.
Previous outbreaks in the United States and Canada had been linked to bagged salad, cilantro, basil, raspberries, snow peas and green onions. Those historical links helped explain why public-health teams were examining fresh produce, but they did not establish the source of Michigan’s 2026 illnesses.
Officials also addressed concern about the regional water system. At a Detroit City Council meeting, council president James Tate read a statement saying no evidence connected the city’s drinking water to the outbreak. The Great Lakes Water Authority likewise said there was no indication that the water it supplied caused or contributed to the infections.
The authority said its drinking-water treatment was designed to remove this type of contaminant. Its wastewater process used chlorine before discharge, although Cyclospora was not regulated or routinely tested under its discharge permit. The authority’s research group was consulting academic partners about whether suitable testing could detect the parasite in treated wastewater effluent.
Health guidance urged consumers to wash produce and, when possible, cook it rather than eat it raw. Such recommendations were precautionary while investigators continued interviews, testing and food traceback. They did not mean all lettuce or salad products had been declared unsafe.
The rapid one-day rise documented the reporting pace at that stage, not necessarily 669 infections acquired within 24 hours. With hospitalization data several days older than the case count and no confirmed source, the available numbers offered a developing snapshot. Further laboratory and supply-chain evidence was still needed to connect the statewide illnesses to any specific item.
The case distribution also showed that the investigation was no longer confined to the county where the outbreak first attracted attention. Reports from 56 counties required statewide coordination even though southeastern counties had the largest known totals. Officials identified no single exposure shared by every county and no estimate of unreported infections.
