Cyclospora Outbreak 2026: Why "Explosive Diarrhea" Cases Are Surging Across 31+ U.S. States (Full Guide)

Last updated: July 14, 2026

If your feed is suddenly full of headlines about a parasite causing "explosive diarrhea" across America, you're not imagining it. As of mid-July 2026, the United States is in the middle of one of the worst cyclosporiasis seasons in over a decade — with more than 4,000 reported or confirmed cases nationwide, dozens of hospitalizations, and health departments in over 30 states scrambling to trace the source.

This isn't your average summer stomach bug. It's caused by a microscopic parasite called Cyclospora cayetanensis, and it's spreading through the U.S. food supply in ways investigators still can't fully explain. Here's everything you need to know — what it is, where it's spreading, why cases are exploding this year, and how to protect yourself and your family.

What Is Cyclosporiasis, Exactly?

Cyclosporiasis is an intestinal infection caused by Cyclospora cayetanensis, a single-celled parasite too small to see without a microscope. Unlike bacteria such as E. coli or Salmonella, this parasite has an unusual life cycle: it needs time outside the human body — usually in soil or water — to mature into a form that can actually infect someone. That's a big part of why it's so hard to trace back to a single source.

People typically get infected by eating food or drinking water contaminated with feces carrying the parasite. It is not something you catch from being near a sick person the way you might catch a cold or the flu, because the parasite isn't infectious right away after leaving the body.

Symptoms to Watch For

The hallmark symptom is watery diarrhea, often described by health officials as "frequent and sometimes explosive." Beyond that, people report:

• Loss of appetite and unexplained weight loss

• Abdominal cramping and bloating

• Nausea and fatigue

• Symptoms that fade, then unexpectedly return days later

Left untreated, symptoms can drag on for weeks or even a month. The illness is rarely fatal, but it can be miserable, and severe cases can lead to dehydration serious enough to require hospitalization.

How Bad Is the 2026 Outbreak, Really?

This is the part that's got public health officials worried. According to CDC surveillance data, the agency had confirmed 843 domestic cases across 31 states as of July 9, 2026 — but independent tallies paint a much bigger picture. News organizations tracking state-by-state health department data put the real number well above 4,000 cases nationally as of July 13, compared to roughly 2,700 cases in all of 2025.

To put that in perspective: mid-June saw just 145 confirmed cases. Within about a month, that number multiplied more than tenfold.

States hit hardest so far:

• Michigan — the epicenter of the outbreak, with over 2,600 cases and 44 hospitalizations as of July 9. Health officials there describe the surge as "sudden and large," roughly 50 times the state's typical annual average of 40–50 cases.

• New York — around 470 cases reported since May 1.

• Ohio — over 360 cases and dozens of hospitalizations.

• Illinois, Texas, North Carolina, and Florida — each reporting well over 100 cases.

In total, 31 to 32 states have reported cases, meaning more than half the country now has confirmed cyclosporiasis activity in some form.

What's Causing the Outbreak?

This is the frustrating part: as of this writing, investigators have not identified a definitive source. Michigan health officials, who are leading much of the investigation given their outlier case numbers, say early evidence points toward lettuce or salad greens as a common thread — but they've been careful to note that no specific grower, supplier, or product has been confirmed, and other foods haven't been ruled out.

"Early information has shown lettuce as a common product that regularly comes up during the investigation," Dr. Natasha Bagdasarian, Michigan's chief medical executive, said in a statement.

Historically, cyclosporiasis outbreaks in the U.S. have been linked to a fairly consistent list of fresh produce items:

• Bagged lettuce and salad mixes

• Fresh basil and cilantro

• Snow peas

• Raspberries

• Green onions

These foods share two things in common: they're often eaten raw, and they're grown close to the ground where contaminated irrigation water or soil can make contact with the crop before it's ever harvested.

Interestingly, the CDC itself has pushed back a bit on the "single outbreak" framing, stating it has "no evidence of a single, multistate Cyclospora outbreak" and that it's still investigating whether current case clusters are connected or represent multiple, unrelated contamination events happening at the same time.

A Surveillance Gap Is Making This Harder to Track

There's a policy wrinkle complicating the investigation. Before July 2025, a CDC monitoring network called FoodNet tracked eight major foodborne pathogens, including cyclospora. That network has since been scaled back to track only two pathogens — Salmonella and a dangerous strain of E. coli — with reporting on the rest, including cyclospora, now optional for many states.

Former CDC Director Dr. Robert Redfield told reporters the timing couldn't be worse: "I don't think it's in our country's interest to cut these programs back. Surveillance is sort of the key to early identification." Public health experts note this gap means the real scope of the outbreak is almost certainly larger than what's being officially reported, since many mild cases go untested entirely.

Who's Getting Sick?

CDC data offers a demographic snapshot of domestic cases reported so far in 2026:

• Ages ranged from 5 to 88 years old, with a median age of 44

• 59% of patients were female

• Median symptom onset was tied closely to the outbreak's rapid escalation through late June

A separate group of 343 cases were linked to international travel rather than domestic food exposure, reported across 32 states, skewing slightly older (median age 46).

As of the CDC's most recent count, 86 hospitalizations have been reported nationwide, with no deaths.

How Is Cyclosporiasis Treated?

The standard treatment is a 7-to-10-day course of the antibiotic combination sulfamethoxazole-trimethoprim, sold under brand names like Bactrim or Septra. Alongside medication, doctors recommend rest and staying well-hydrated, since prolonged watery diarrhea can quickly lead to dehydration — the main reason people end up hospitalized.

If you've had unexplained, persistent diarrhea for several days — especially after eating fresh salad, herbs, or berries — doctors recommend seeing a healthcare provider for testing rather than assuming it's a routine stomach bug. Cyclospora requires a specific lab test to detect; it won't necessarily show up on a standard stool culture.

How to Protect Yourself: Food Safety Tips That Actually Work

Health departments across affected states, including Michigan's, have issued a consistent set of recommendations for reducing your risk:

For lettuce and leafy greens:

• Buy whole heads of lettuce instead of pre-washed, bagged salad mixes when possible

• Remove and discard the outer two to three leaves

• Wash remaining leaves thoroughly under running water

• Cook leafy greens when you can — heat kills the parasite

For herbs like cilantro and basil:

• Separate the leaves and rinse thoroughly under running water

• Cooking is the safest option if you're worried about exposure

For green onions:

• Trim the root end and remove the outer layer before washing thoroughly

For raspberries:

• Their bumpy surface is nearly impossible to fully clean, so consider using cooked or frozen raspberries instead of fresh ones during outbreak periods (freezing reduces but doesn't eliminate the parasite)

General kitchen hygiene:

• Heat food to at least 158°F (70°C) — this is the threshold that reliably kills Cyclospora

• Wash all fresh produce under clean running water, even items you plan to peel

• Scrub firm produce like melons and cucumbers with a dedicated produce brush

• Cut away any bruised or damaged sections of fruits and vegetables before eating

• Wash your hands with soap and water before and after handling food

• Sanitize cutting boards, countertops, and utensils used for fresh produce

Unfortunately, experts are candid that washing alone can't guarantee full protection — cyclospora organisms can cling tightly to the surface of produce in a way that plain rinsing doesn't always remove. Cooking remains the only fully reliable method.

Is This a National Emergency?

Not officially — at least not yet. As of the most recent updates, health officials have stopped short of declaring this a national health emergency, even as case numbers climb well past historical norms. The CDC and FDA continue to monitor clusters across multiple states, and additional cases are expected to be identified in the coming weeks due to reporting delays that typically run several weeks behind real-world infection rates.

Public health experts, including academic microbiologists tracking the outbreak, are striking a "aware, not alarmed" tone — emphasizing that while case numbers are genuinely unusual for 2026, the illness itself is treatable and not fatal when properly managed.

The Bottom Line

The 2026 cyclospora outbreak is real, it's growing, and it's already surpassed last year's entire annual case count in a matter of weeks — with Michigan bearing the brunt of it. Investigators suspect fresh produce, possibly lettuce, but haven't confirmed a definitive source, which means the safest move for now is simple: wash your produce carefully, cook leafy greens when you can, and don't shrug off diarrhea that lingers more than a few days. If you're experiencing symptoms, especially after eating fresh salad greens, herbs, or berries, talk to a healthcare provider about getting tested.

This story is still developing. Health departments are updating case counts weekly, and the source investigation is ongoing — we'll keep this guide updated as new information comes in.

Frequently Asked Questions

Is cyclosporiasis contagious from person to person? No, not directly. The parasite needs time outside the human body to mature before it can infect someone else, so it doesn't spread the way a cold or flu virus does.

How long do symptoms last? Symptoms can last anywhere from a few days to over a month if untreated, and may improve and then unexpectedly return.

What food has been linked to this outbreak? Investigators haven't confirmed a definitive source, but early evidence in Michigan points toward lettuce or salad greens. Previous outbreaks have also been tied to basil, cilantro, snow peas, and raspberries.

Should I stop eating salad? Health officials aren't recommending people avoid produce entirely — the guidance is to wash thoroughly, buy whole heads of lettuce over pre-bagged mixes, and cook greens when possible, especially in outbreak hotspot states.

Sources

CDC Cyclosporiasis Surveillance, Michigan Department of Health and Human Services, CNN, NPR, PBS NewsHour, ABC News, NBC News/TODAY, Newsweek, U.S. News & World Report, Texas State University Newsroom.