A summer parasite outbreak is testing U.S. food-safety surveillance as cases climb across 31 states

By Zara Desai

A fast-growing summer outbreak of cyclosporiasis, an intestinal illness commonly linked to contaminated fresh produce, has become the clearest health story of the day: not because it is causing mass deaths, but because it exposes how hard it can be to trace a foodborne parasite while people are still getting sick.

The Centers for Disease Control and Prevention said on July 10 that, since May 1, it had received reports of 843 confirmed domestically acquired cases of cyclosporiasis across 31 states. The agency also said it was aware of more than 1,500 additional cases that require further analysis to confirm whether they were domestically acquired cyclosporiasis. Eighty-six people among the confirmed cases had been hospitalized, and no deaths had been reported.

Those national numbers almost certainly lag what state investigators are seeing in real time. The CDC explicitly warned that state counts are likely higher than the federal numbers because initial reports must be confirmed, categorized and transmitted before they appear in federal surveillance. The agency said multiple states reported increases in the last two weeks compared with the same period in 2025, and that case counts are expected to rise as delayed reports come in.

The outbreak is most visible in Michigan and nearby parts of Ohio. The Associated Press reported Wednesday that Michigan had reached 992 diagnosed cases, including about 40 hospitalizations, after first announcing the outbreak last week with more than 170 known cases in the southeastern part of the state. Michigan usually identifies about 50 cases a year. Lucas County, Ohio, reported 306 cases as of Wednesday, while northwest Ohio had seen more than 500 cases.

That makes the story more than a local stomach-bug alert. It is a live test of the country’s foodborne-illness surveillance system during peak produce season, when Americans are eating more raw fruits, herbs and vegetables and when cyclospora outbreaks tend to appear.

“Cases seem to be surging in and around southeastern Michigan,” AP wrote, while noting that officials do not consider the situation a national health emergency. The distinction matters. This is serious for people who become ill, and it is large enough to demand attention from public-health agencies. But the available evidence does not support panic, nor does it point to a single food item that consumers nationwide should avoid.

What officials know — and what they still do not

Cyclosporiasis is caused by Cyclospora, a microscopic parasite that infects the intestines. The CDC describes the illness as a gastrointestinal disease and says symptoms can include watery diarrhea, loss of appetite and weight loss. In AP’s summary of CDC language, the diarrhea may be frequent and sometimes explosive. The illness is generally treatable, and AP reported that it is not usually life-threatening.

The harder question is where this outbreak began.

As of the latest CDC and FDA updates reviewed Saturday, investigators had not publicly identified a single contaminated product, farm, distributor or restaurant chain. The FDA’s active outbreak table lists multiple Cyclospora investigations tied to “not yet identified” products. Two new Cyclospora outbreaks, FDA reference numbers 1385 and 1384, were added July 8 with traceback initiated. Another active Cyclospora investigation, reference number 1381, was added June 17. The FDA says it does not publicly name a product category or specific product until there is enough evidence to implicate it.

That restraint can be frustrating for readers who want a clean answer: Which lettuce? Which herb? Which store? But it is also a core safety principle. Naming the wrong food can damage businesses, confuse consumers and leave the real source circulating.

Cyclospora investigations are especially difficult. The parasite has historically been linked to produce exposed to feces-contaminated water. AP noted that past outbreaks have involved raspberries, basil, cilantro, snow peas and salad mixes. A single ingredient such as cilantro or basil can appear in many foods, restaurants and grocery products, making patient food histories hard to compare. Distribution networks can also send contaminated ingredients into both retail and food-service channels, blurring the trail.

There are technical limits, too. AP quoted Melanie Firestone, a University of Minnesota foodborne-illness researcher, saying that some food-poisoning tests are not designed to detect cyclospora, contributing to underreporting. AP also reported that technicians cannot grow the parasite in labs, which makes it harder to build evidence from contaminated produce.

The result is a familiar food-safety paradox: the larger the investigation gets, the more urgent the public wants answers, but the more careful agencies must be about what they can actually prove.

Why this outbreak stands out

Foodborne outbreaks are common enough that many never become national news. This one stands out for three reasons.

First, the case count is unusually high for cyclospora. AP reported that only a small number of documented U.S. outbreaks in the last 20 years have surpassed 1,000 cases. Examples include a 1997 outbreak tied to Guatemalan raspberries that sickened more than 1,000 people in the United States and Canada, and a 2019 outbreak linked to Mexican basil that sickened more than 2,400.

Second, the CDC’s confirmed national count is already broad: 843 cases in 31 states, with 86 hospitalizations and no deaths reported as of July 9. The agency also says it is aware of more than 1,500 cases needing further analysis. That does not mean all of those cases will be confirmed or tied to one source. It does mean the investigation is larger than the official confirmed number alone suggests.

Third, the outbreak is unfolding in the messy overlap between state and federal reporting. Michigan’s visible surge may partly reflect aggressive state investigation and reporting, according to Dr. Natasha Bagdasarian, Michigan’s chief medical executive, whom AP quoted saying that the state’s reporting may be “part of the reason why this looks like a Michigan problem.” At the same time, Bagdasarian told AP that “there is clearly a linked outbreak happening right now.”

Those two ideas can both be true. A state can look like the epicenter because it is finding cases quickly, and a linked outbreak can still be real.

What readers should do with the risk

The reader-safe takeaway is not “stop eating produce.” It is: treat raw produce as a real food-safety surface, especially during an active outbreak whose source has not been named.

The CDC says the best way to prevent cyclosporiasis is to avoid food or water that may be contaminated with feces, and it recommends standard safe-handling steps for fresh produce: wash hands with soap and water before and after handling raw fruits and vegetables; wash produce under running water before eating, cutting or cooking; scrub firm fruits and vegetables such as melons and cucumbers with a clean produce brush; cut away damaged or bruised areas; and refrigerate cut, peeled or cooked produce within two hours.

The agency also notes a frustrating limit: routine chemical disinfection or sanitization is unlikely to kill Cyclospora in food or water in areas where the parasite is common. AP’s reporting adds another practical caution: washing can reduce risk, but cyclospora can stick to some foods, so washing may not eliminate risk entirely.

Michigan officials, while investigating the possible source, have recommended buying whole heads of lettuce rather than prewashed bagged lettuce or salad mixes, removing the outer two to three leaves and washing the remaining leaves under running water. They have also recommended cooking vegetables when possible.

That guidance should be read as public-health risk reduction, not a guarantee. It also should not be stretched into claims the evidence does not support. Officials have not said all bagged salads are unsafe. They have not named a brand. They have not identified a single contaminated farm. And no federal advisory reviewed Saturday told the public to avoid a specific nationally distributed product because of this cyclospora investigation.

For people who are already sick, the CDC’s public-health surveillance page says people with symptoms such as watery diarrhea, appetite loss and weight loss should see a healthcare provider, who can test and treat cyclosporiasis. That is not a substitute for individual medical advice; it is the agency’s general public-health guidance.

The bigger public-health lesson

This outbreak is landing at a sensitive moment for public trust in health agencies. Foodborne illness investigations depend on ordinary people reporting symptoms, clinicians ordering the right tests, laboratories identifying the pathogen, local and state health departments interviewing patients, and federal agencies looking for patterns across jurisdictions. Every weak link slows the answer.

The CDC says cyclosporiasis is nationally notifiable and reportable in 47 states, the District of Columbia and New York City. But notifiable does not mean instant. In its July 10 update, the agency said it assumes a six-week lag between illness onset and case reporting to CDC. That means today’s numbers are partly a rearview mirror.

That lag is especially important with a parasite whose outbreaks are seasonal. The CDC considers the cyclosporiasis season to run from May 1 through August 31, though clusters can appear outside that period. This year’s outbreak season began May 1, and cases with illness onset dates in the CDC’s current data range from May 1 to July 5, with a median illness onset date of June 18.

In other words: the public is hearing about a surge that began weeks ago, investigators are still sorting which cases are connected, and produce supply chains have already moved forward.

That does not mean the system is failing. It means the system is slow by design because it has to distinguish confirmed, probable, domestic, travel-associated and unrelated cases. But it does mean readers should understand why public-health officials sometimes sound cautious when the public wants certainty.

No single villain yet

The FDA’s outbreak table is useful because it shows the state of evidence without overclaiming. For Cyclospora, current active investigations list “not yet identified” products and indicate that traceback work has begun. In plain English, that means investigators are working backward through supply chains from what sick people remember eating and where those foods were purchased or served.

That is not glamorous work. It is interview forms, receipts, distributor records, shipment dates and lab results. It can produce a sharp answer. It can also end with no definitive source, especially if the contaminated ingredient was perishable and long gone before investigators knew what to test.

AP reported that cyclospora outbreaks have increased over the past decade, with notable spikes in 2018 and 2019. Experts cited by AP attribute the increase to climate change and better detection. Both explanations point in the same direction for readers: these events are not necessarily random one-offs, and public-health surveillance needs enough capacity to detect them quickly.

The food system is built for speed, seasonality and national distribution. Parasite investigations are built for confirmation. When those timelines collide, uncertainty is not a failure of communication; it is the condition reporters and readers have to sit with until the evidence catches up.

What to watch next

The next meaningful update will not be a hotter headline. It will be whether federal or state investigators identify a common food source, whether the case curve continues rising after reporting lags are accounted for, and whether any advisory names a product with specific consumer action.

For now, the strongest shared facts are these: CDC has confirmed 843 domestically acquired cases across 31 states since May 1, with 86 hospitalizations and no deaths reported; CDC is aware of more than 1,500 additional cases requiring analysis; Michigan and northwest Ohio are reporting major clusters; FDA has multiple active Cyclospora traceback investigations involving not-yet-identified products; and no single source has been publicly identified.

That is enough to make this the day’s top health story. It is also enough to resist turning it into a food panic.

The better frame is narrower and more useful: a summertime parasite outbreak is spreading through the reporting system faster than investigators can publicly name a source, and readers deserve both practical caution and honest uncertainty.

Sources

• Centers for Disease Control and Prevention, “Surveillance of Cyclosporiasis,” updated July 10, 2026: https://www.cdc.gov/cyclosporiasis/php/surveillance/index.html
• Centers for Disease Control and Prevention, “Preventing Cyclosporiasis,” updated February 29, 2024: https://www.cdc.gov/cyclosporiasis/prevention/index.html
• U.S. Food and Drug Administration, “Investigations of Foodborne Illness Outbreaks,” active investigations table reviewed July 11, 2026: https://www.fda.gov/food/outbreaks-foodborne-illness/investigations-foodborne-illness-outbreaks
• Associated Press, “Outbreak of diarrhea-causing parasite grows to more than 1,000 cases,” updated July 9, 2026: https://apnews.com/article/cyclospora-outbreak-michigan-31e5e0034d39e85c844065a2bd593ecb
• Associated Press, “How to stay safe and still enjoy produce this summer with the outbreak of diarrhea-causing parasite,” updated July 10, 2026: https://apnews.com/article/cyclospora-produce-washing-tips-022730ccbc514e15b1f0021c47bf1b68