Travel warning as stomach parasite spreads to 18 US states

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A growing outbreak of a microscopic parasite that causes severe stomach illness has sickened at least 145 people across 18 U.S. states since early May, raising concerns for travelers at the height of the summer vacation season.

Parasite-linked illnesses climb as summer travel peaks

Publicly available surveillance data from the Centers for Disease Control and Prevention indicate that 145 laboratory-confirmed cases of cyclosporiasis were reported between May 1 and June 16, 2026, in people who acquired the infection in the United States. Reporting has since expanded to 18 states as additional jurisdictions confirm cases, according to recent media coverage that draws on state and federal updates.

The intestinal illness is caused by Cyclospora cayetanensis, a single-celled parasite that infects the small intestine. Infections can trigger prolonged, sometimes severe gastrointestinal symptoms that interrupt daily life and disrupt travel plans. National case counts for this year already exceed those seen over the same period in 2025, based on compiled CDC figures cited in recent news reports.

Coverage from outlets including Axios, The Guardian and regional broadcasters notes that the current numbers likely underestimate the true scale of infection, because diagnosis requires specific stool testing that is not always ordered for people with typical summer stomach complaints. Health experts quoted in those reports say that many people with milder symptoms may never be tested or reported.

While there is no indication of a nationwide health emergency, the pattern is significant for people on the move in late spring and summer, when Americans typically increase domestic travel, dine out more frequently and consume larger amounts of raw fruits, salads and herbs.

What travelers should know about cyclosporiasis

Cyclosporiasis typically develops after a person consumes food or water contaminated with microscopic Cyclospora oocysts shed in human feces. CDC background materials and past outbreak investigations describe the infection as foodborne or waterborne, rather than spread from person to person. The parasite needs time in the environment to become infectious, so direct contact with an ill person is not considered a typical route of transmission.

Symptoms usually start about one week after exposure, though the incubation period can range from a few days to two weeks. According to federal fact sheets and medical references, the most common complaints include frequent watery diarrhea, sometimes described in news coverage as “explosive,” along with stomach cramping, bloating, nausea, loss of appetite, fatigue and low-grade fever. Some patients also report weight loss and body aches.

Illness can last several days to more than a month and may follow a relapsing pattern if untreated. Antibiotics are generally effective, but over-the-counter treatments alone may not clear the parasite. Published guidance advises that people with persistent diarrhea lasting more than a few days, especially after eating fresh produce or traveling, should seek medical evaluation and ask whether testing for Cyclospora is appropriate.

For most otherwise healthy travelers, cyclosporiasis is uncomfortable and disruptive rather than life threatening. However, reports from Michigan and other hard-hit states describe dozens of hospitalizations, underlining the potential severity for some patients, particularly those with underlying health conditions or limited access to prompt care.

States reporting cases and emerging hotspots

CDC summary maps and regional news outlets show that at least 18 states have reported domestically acquired cyclosporiasis cases so far this season. Media coverage highlights Michigan, Texas, Ohio, New York, Florida, Pennsylvania, Virginia, North Carolina and Maryland among the affected states, alongside others where smaller clusters have been identified.

Michigan has emerged as a major hotspot. According to recent Associated Press reporting that draws on state health department figures, nearly 1,000 people there have been diagnosed this year, making it the largest such outbreak in that state’s history and one of the largest in the United States in recent years. Local coverage notes that reported cases surged from roughly 170 in late June to hundreds more in early July.

Neighboring regions are also reporting elevated activity. News reports from Ohio indicate that counties along the Michigan border have documented hundreds of cases, while Florida outlets describe a “fast-moving” rise tied to the broader multistate pattern. Stations in North Carolina, Pennsylvania and the Mid-Atlantic have likewise confirmed dozens of infections through interviews with state health representatives and reviews of public records.

Despite the growing case counts, CDC surveillance summaries cited by national media emphasize that there is currently no evidence that all infections are linked to a single contaminated product or nationwide supply chain event. Instead, investigators are examining several clusters that may have different food sources, which can make it harder for travelers to identify specific items to avoid.

Suspected food links and why the source is hard to find

Federal technical reports and prior Morbidity and Mortality Weekly Report articles on cyclosporiasis describe a long history of outbreaks tied to fresh produce, including imported cilantro, basil, leafy greens and pre-packaged salads. The parasite thrives in warm, moist environments, and contaminated irrigation water and poor sanitation can allow it to enter the food supply.

In the current season, investigators are again focusing on fresh fruits, vegetables and herbs that are commonly eaten raw. However, according to recent analyses in outlets such as Politifact and Axios, no single ingredient has yet been publicly identified as the definitive source for the multistate uptick, and some state-level spikes appear to be tracked separately from the national tally.

Experts cited in these reports explain that tracing Cyclospora is especially challenging because the contaminated item may be a minor ingredient, such as chopped herbs or garnish, that appears in many different dishes at restaurants and in home kitchens. By the time health departments detect patterns in lab-confirmed cases, the suspected produce may no longer be available for testing.

Genotyping tools and detailed interviews about what patients ate can help narrow down possibilities, but food-distribution networks that send the same lot of produce to multiple states and both restaurants and grocery stores can obscure the trail. As a result, federal and state agencies sometimes conclude investigations without naming a specific product, even when environmental conditions strongly suggest a produce-related source.

Practical precautions for people on the move

For travelers, the current cyclosporiasis pattern reinforces long-standing food-safety advice rather than introducing entirely new rules. Public health guidance summarized in recent coverage recommends thoroughly rinsing fresh fruits, vegetables and herbs under running water, removing visible dirt and discarding outer leaves of lettuce or cabbage when possible. While washing may not completely eliminate Cyclospora, experts note that it can reduce overall contamination and remove other pathogens.

People on road trips, staying in vacation rentals or eating frequently at restaurants may want to be especially cautious with raw produce that cannot be peeled, such as mixed salads and ready-made garnishes. Choosing cooked options when food hygiene is uncertain, keeping perishable items cold and practicing careful handwashing before meals can all help lower risk.

Travelers who develop persistent watery diarrhea, stomach cramps or other symptoms after eating fresh produce, particularly in states currently reporting clusters, are encouraged by published health advisories to seek care promptly. Providing clinicians with detailed information about recent foods and destinations can support timely testing and treatment.

Because national surveillance numbers often lag behind on-the-ground reality, people planning trips in the coming weeks may wish to review the latest summaries from their destination state’s health department before departure. While most visits will proceed without incident, awareness of the ongoing Cyclospora activity can help travelers make more informed choices at the table and respond quickly if illness strikes.