If you’ve seen a meme joking about “diarrhea lettuce” lately, it’s not just an absurd punchline — it’s riffing on a genuinely large, ongoing foodborne illness outbreak that’s been spreading across the U.S. this summer. Here’s what’s actually happening, and why lettuce keeps ending up at the center of these headlines.
What’s Actually Going On
<cite index=”22-1″>An outbreak of diarrhea caused by the parasite cyclospora has risen to more than 3,000 cases in Michigan and Ohio, with the ongoing investigation suggesting lettuce or salad greens may be the source.</cite> <cite index=”29-1″>The outbreak has now been reported in 31 states nationally, according to the CDC, though Michigan has by far the largest share of cases, with 2,640 reported as of mid-July.</cite>
<cite index=”22-1″>Michigan’s chief medical executive said early investigation data has repeatedly pointed to lettuce as a common product coming up across interviews with sick patients, though officials stress that no specific type, grower, or supplier has been confirmed as the source, and other foods haven’t been ruled out.</cite>
What Is Cyclospora, Exactly?
Cyclospora is a microscopic parasite, not a bacteria like E. coli or Salmonella, that causes an intestinal infection called cyclosporiasis. <cite index=”28-1″>It typically affects people who’ve eaten contaminated produce, including lettuce, basil, cilantro, snow peas, and raspberries.</cite> The infection causes watery, sometimes prolonged diarrhea, along with symptoms like cramping, bloating, fatigue, and loss of appetite. Unlike a quick 24-hour stomach bug, cyclospora infections can drag on for weeks if untreated.
Why Is It So Hard to Pin Down the Source?
<cite index=”22-1″>Cyclosporiasis cases are notoriously difficult for investigators to trace, partly because patients may need to recall what they ate weeks earlier, genomic testing for the parasite is complex, and public health surveillance systems that track foodborne illness have recently faced significant cuts.</cite> <cite index=”22-1″>In fact, in the wake of staffing and funding cuts to public health agencies in 2025, the CDC scaled back its FoodNet surveillance system, which used to track eight different foodborne pathogens including cyclospora — now the network only actively collects data on two: salmonella and a particularly dangerous strain of E. coli.</cite>
That gap in tracking capacity is part of why officials can say “lettuce keeps showing up” without yet being able to name a specific brand or supplier — the infrastructure to move faster simply isn’t what it used to be.
