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Federal health officials have expanded the list of states reporting domestically acquired cyclospora infections, adding Oregon, South Dakota, Vermont and Delaware, as the Centers for Disease Control and Prevention (CDC) reported a sharp increase in confirmed cases nationwide on Tuesday.
Cyclospora is a microscopic parasite that causes cyclosporiasis, a gastrointestinal illness. According to the CDC's latest surveillance update published July 28, the number of laboratory-confirmed domestically acquired cases has climbed to 6,707 across 45 states. The previous update, which was posted last week, was for 4,173 confirmed cases across 41 states.
The latest figures represent a jump of roughly 2,500 confirmed cases compared with the agency's previous update, underscoring the scale of what has become one of the largest cyclospora seasons in recent years. While the illness can be severe and disruptive, particularly for older adults and people with weakened immune systems, the CDC reports that no deaths have been linked to the domestically acquired cases recorded this year. There have been 423 hospitalizations reported.
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Newsweek reached out to the CDC by email for comment.
How Does Cyclospora Start?
Cyclospora infections begin when a person consumes food or water contaminated with the microscopic parasite Cyclospora cayetanensis. Unlike many foodborne bacteria, cyclospora does not typically spread directly from one person to another because the parasite needs time in the environment to become infectious. Fresh produce is most often implicated in U.S. outbreaks, with leafy greens, herbs and berries among the foods previously linked to infections.
Once ingested, the parasite can cause a gastrointestinal illness marked by frequent watery diarrhea, stomach cramps, bloating, nausea, fatigue and weight loss. Symptoms can last for days or even weeks if left untreated. This year's increase in cases has prompted heightened surveillance by federal and state health officials, who are investigating several clusters of illness nationwide.
Map Shows Cyclospora Outbreak Still Spreading
The CDC's latest surveillance update suggests cyclospora activity remains widespread across the country, with the CDC's map reflecting the continued geographic expansion of reported illnesses.
Health officials caution that the map likely understates the true scope of infections because not everyone who gets sick seeks medical care or receives testing. The CDC also estimates there is approximately a six-week reporting lag between illness onset and national reporting, meaning additional cases are expected to be added in future updates.
Montana, New Mexico, Hawaii, Maine, and South Carolina are the only states without confirmed cyclospora cases, according to CDC data.
In addition to the 6,707 laboratory-confirmed domestically acquired infections, the CDC said it is aware of more than 11,500 additional cases that have not yet been laboratory confirmed or require further investigation, including determining whether patients traveled internationally before becoming ill. Many of those additional reports have come from Michigan and Ohio, the agency said.
Which States Have Seen the Highest Number of Cases?
The CDC's surveillance map groups states by case-count ranges rather than publishing exact figures directly on the graphic. The agency notes that some states have reported substantially more cases than others, with multiple jurisdictions experiencing far higher numbers than seen during the same period in 2025.
Michigan and Ohio are the states with the highest cyclospora case counts, if both confirmed and unconfirmed cases are taken into account, according to the CDC map. Final rankings may continue to shift as laboratory testing is completed and more reports are verified.
Which Fruits, Vegetables Are Safe from Cyclospora?
Outbreaks are most often linked to fresh produce consumed raw, since cooking can kill the parasite. This year's major multistate outbreak that has affected at least nine states has been linked to iceberg lettuce, prompting an investigation by the CDC, Food and Drug Administration (FDA) and state health officials.
Food safety experts stress that no fresh produce is completely risk-free during a cyclospora outbreak, since contamination can occur before a fruit or vegetable reaches consumers. However, some products may be lower risk than others. Produce with a thick outer skin or peel that is removed before eating—such as bananas, avocados, oranges, pineapples, mangoes and kiwi—offers an extra layer of protection because the edible portion is shielded from contamination. Experts have also suggested that whole heads of lettuce or cabbage may be preferable to pre-cut or bagged salads, since consumers can discard the outer leaves before washing and eating the inner layers.
By contrast, bagged greens, chopped lettuce, fresh herbs such as cilantro and basil, and berries have been linked to previous cyclospora outbreaks because the parasite can cling to rough surfaces, crevices and cut edges that are difficult to clean completely. Cooking vegetables may provide additional protection, as heat is known to kill cyclospora, whereas washing alone cannot guarantee removal of the parasite.
Consumers should pay close attention to recall notices and public-health advisories. On July 17, Taylor Farms recalled certain iceberg lettuce products sourced from central Mexico as investigators worked to trace illnesses linked to the ongoing outbreak, although a Taylor Farms spokesperson previously told Newsweek that none of their products tested positive for the parasite. The CDC, FDA, and state health departments are continuing to trace illnesses and determine whether additional food products may be involved.
How Many Cases Aren't Reported?
The CDC says the official count represents only laboratory-confirmed cases that have been investigated and reported through public health surveillance systems.
At the same time, the CDC said it is aware of more than 11,500 additional cases that either have not yet been laboratory confirmed or require further analysis, such as determining whether patients traveled internationally before becoming sick. The agency also notes that the true number of illnesses is likely even higher because some people recover without seeking medical care and are never tested, leaving many infections outside official tallies.
Cyclospora cases typically increase during the warmer months, with the CDC noting that the U.S. cyclosporiasis season generally runs from May through August. Because the outbreak season is still ongoing and additional reports are under review, health officials expect case counts to keep climbing in the coming weeks.
Cyclosporiasis Outbreak
Check out Newsweek's latest coverage:
- Taylor Farms Says FDA Has Apologized Over ‘False Positive’ Cyclospora Test
- Cyclospora Patient Reveals What Symptoms are Really Like as Outbreak Spreads
- Which Salad Greens Are Safe From Cyclospora Parasite? List of Companies, Where to Buy
- What Kills Cyclospora? Food Safety Tips Amid Explosive Diarrhea Outbreaks
- Medicine To Treat ‘Explosive’ Diarrhea Outbreaks Could Cause More Diarrhea
- Cyclospora Isn’t the Only Parasite in Fresh Produce—Experts Warn of Others
- How Long Does Cyclospora Incubate? Symptoms To Watch For, How to Treat It
- Where Does Cyclospora Parasite Come From? How to Protect Yourself
Contact Newsweek editors for this story: Jason Lemon and Robert Greenall
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