The cyclosporiasis season usually ends in August. Experts say this outbreak could last longer than normal.

Parsley could be responsible for some of the cyclospora infections in the U.S., which has been grappling with several likely outbreaks of the parasite this summer.

The biggest-ever cyclospora outbreak in the U.S. still shows no signs of slowing down.

Michigan has now recorded 10,077 cases, and at least 160 people have been hospitalized. The state, which usually only has about 50 cases a year, was the first to publicly identify iceberg lettuce as the possible culprit spreading Cyclospora cayetanensis, the parasite that causes watery diarrhea or other gastrointestinal issues associated with cyclosporiasis.

This cyclospora outbreak is far different than outbreaks of the past. One reason that makes it so challenging is that there is still no confirmed source, leaving Americans confused about whether to eat any leafy greens or herbs.

"The prolonged time to identify a confirmed source for this cyclospora outbreak is unusual," said David Hamer, a professor of global health and medicine at Boston University, in an email. "Past outbreaks have generally been smaller, and the source has been identified faster."

Hamer believes several factors are to blame - including recent cuts to federal funding for outbreak response and surveillance, the theory that there is more than one outbreak underway, and the prevalence of leafy greens on dining-room tables in the summer months. Researchers also say there is a lot unknown about cyclospora, which behaves differently and is more difficult to track than other foodborne bacteria like E. Coli or salmonella.

"Leafy greens have had many problems in the last decade with microbial contaminants, not just cyclospora," said Felicia Wu, a professor of food safety at Michigan State University, in an email. "In some ways it's not a surprise, but the specific contaminant, cyclospora, is more unusual than E. coli and salmonella problems in leafy greens."

The complexity of this outbreak also raises questions about whether it could last longer than past outbreaks, which historically wane in August.

"Cyclospora does tend to be seasonal," Hamer said, "but there is a risk, between the global nature of our food supply and climate change allowing for longer growing seasons in some locations, that this will persist longer than norm."

It's a view echoed by Lynette Johnston, assistant professor and food-safety extension specialist at North Carolina State University.

"Cyclospora cases usually drop off towards the latter end of the summer," Johnston said. "I would expect that's going to be the same, but [this] summer is a little different because of the magnitude."

There are now 6,707 confirmed cases of cyclosporiasis in 45 states, and another 11,500 people are believed to have cyclospora, according to the Centers for Disease Control and Prevention's latest update on Tuesday. More than 400 people have been hospitalized in the U.S.

Earlier this month, officials narrowed in on shredded iceberg lettuce grown by Taylor Farms in Mexico and sold to Taco Bell (YUM), saying it's to blame for the outbreak in the Midwest. Taylor Farms, a sprawling farming conglomerate, recalled iceberg lettuce sold by one of its farms in central Mexico. It has also pushed back on the claim, taking aim at federal health investigators over what turned out to be a false-positive test on its produce. As of July 24, Taylor Farms said there are no confirmed tests showing cyclospora on its produce.

That said, researchers believe that different types of produce may be to blame for cyclosporiasis cases in other states - like North Carolina, where there have been 718 cases so far this year, more than double the number of cases reported in 2025. Officials there believe contaminated parsley or cilantro are at fault.

Restaurant chains try to win back consumers

Taco Bell, Chipotle $(CMG)$ and other restaurant chains that rely on lettuce in their meals have seen traffic in their stores decline since the outbreak gained mainstream attention earlier this month.

On July 23, for example, foot traffic was down 21% at Taco Bell restaurants and 12% at the salad chain Chopt compared to the daily average in the first six or so months of the year, according to Placer.ai, which tracks retail traffic. Taco Bell said Thursday that U.S. same-store sales were down 2% from July 1 to July 27.

However, Chris Turner, CEO of Taco Bell parent company Yum Brands, told investors that sales are returning, in part because of new products like the $1 Enchirito and $1 Mexican Pizza - both of which are lettuce-free.

"You've seen a significant decline in Taco Bell's share of the conversation related to this issue," Turner said, according to an AlphaSense transcript. "And the best proof point is that consumers are coming back to the restaurants on a steady basis."

Other companies like Just Salad, a privately held salad chain with locations in several states, are still working to reassure consumers about the safety of their produce. Just Salad said it does not serve iceberg lettuce, buy lettuce from Mexico or purchase precut and preshredded lettuce. "None of this is new, it's always how we have operated," Just Salad CEO Nick Kenner wrote this week on LinkedIn.

Restaurants aren't the only place where Americans are avoiding leafy greens. A survey conducted last week by YouGov and CBS News found that 40% of the roughly 2,200 people surveyed said they are buying less produce at grocery stores as a result of the outbreak.

-Jaimy Lee -Bill Peters