Something is moving through America's salad bowls. Michigan's Department of Health and Human Services issued a formal notice this week identifying lettuce and salad greens as a "potential source" of a cyclosporiasis outbreak that has blown past 2,600 confirmed cases in the state alone — and that number is almost certainly an undercount. Cyclospora infections are notoriously under-reported: the symptoms mimic half a dozen other gut ailments, the parasite requires specialized lab testing to detect, and plenty of people ride out the illness without ever seeing a doctor.

The parasite at the center of this is Cyclospora cayetanensis, a single-celled organism transmitted via food or water contaminated with fecal matter. It does not pass directly from person to person, which means every new case is a fresh exposure to a contaminated source — and the fact that thousands of people across multiple states are getting sick points squarely at something in the commercial food supply rather than a localized environmental event. The Centers for Disease Control and Prevention has been tracking a nationwide increase in cases, and the trajectory puts this outbreak on a path to surpass anything recorded in comparable recent periods.

The illness itself is not subtle. Cyclospora infects the small intestine and, after an incubation period of roughly a week, produces watery and sometimes explosive diarrhea, fatigue, bloating, loss of appetite, and nausea that can cycle on and off for weeks or even months if left untreated. For healthy adults it is rarely fatal, but it is profoundly debilitating — and for immunocompromised individuals, the elderly, and young children, it carries far greater risk. The standard treatment is a course of trimethoprim-sulfamethoxazole, but treatment requires a confirmed diagnosis, which requires a doctor thinking to order the right test.

That gap between exposure and diagnosis is exactly why outbreaks like this one get so large before officials publicly name a source. Investigators have to collect case data, conduct interviews about food history, and cross-reference purchase records before pointing at any single commodity — and the commercial leafy greens supply chain, with its consolidated distributors, multi-state growing regions, and short shelf lives, makes traceback genuinely difficult. The fact that Michigan officials are now willing to say publicly that lettuce and salad greens are the "current" lead is meaningful. It is not a recall, and it is not a certainty, but it reflects a level of epidemiological confidence that officials typically guard carefully.

Cyclospora has a documented history with fresh produce, particularly imported fresh herbs and greens. Major U.S. outbreaks in the 1990s were eventually traced to Guatemalan raspberries. In the years since, fresh cilantro imported from Mexico has been implicated in multiple outbreak investigations. The common thread is produce grown in regions where irrigation water or field sanitation conditions may allow the parasite to contaminate crops — and then consumed raw, since cooking kills Cyclospora. A salad, by definition, does not get cooked. Bagged, pre-washed greens marketed as "ready to eat" offer consumers no additional step to eliminate the risk.

What officials have not yet said publicly — at least not in Monday's release — is which specific product, brand, distributor, or origin country is under the microscope. That matters enormously to consumers standing in front of their refrigerators right now wondering whether to throw out the spring mix. Michigan's guidance, as reported in the department's own release, advises washing produce thoroughly, but the CDC and food safety experts have long noted that standard household washing does not reliably remove Cyclospora from contaminated greens — the parasite can adhere to leaf surfaces in ways that a rinse under the tap will not resolve.

The scale of what is unfolding is worth sitting with. Thousands of cases confirmed across multiple states, a commodity as ubiquitous as bagged salad as the suspected vehicle, and a parasite that the average primary care physician may not immediately think to test for. The conditions for a significant under-reporting problem are all present. Every week that passes without a specific product recall is another week consumers cannot make an informed decision about what they are eating.

Michigan's disclosure that lettuce is a "potential" source is progress. A specific product name, a lot number, a distribution map — that is what a public health response at this scale actually demands.