A multistate outbreak of cyclosporiasis linked to iceberg lettuce has become a major U.S. food-safety investigation, with federal and state health officials expanding their response as the number of reported illnesses rises sharply.
The outbreak is part of an unusually large 2026 cyclosporiasis season. The CDC says it is investigating a multistate outbreak linked to iceberg lettuce in 20 states, while continuing to investigate other Cyclospora illnesses that are not connected to the lettuce outbreak.
The investigation has put fresh attention on the risks associated with contaminated fresh produce and the challenges involved in identifying a parasite that can be difficult to diagnose.
Lettuce Investigation Expands
The FDA and CDC began investigating illnesses associated with processed shredded iceberg lettuce from central Mexico earlier this summer.
The FDA initially announced a five-state investigation involving illnesses linked to certain shredded iceberg lettuce served at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio and West Virginia.
As investigators gathered additional information, the outbreak expanded to more states.
The CDC now describes the investigation as a multistate outbreak linked to iceberg lettuce involving 20 states.
Taylor Farms Lettuce at the Center of the Investigation
Federal investigators identified iceberg lettuce supplied by Taylor Farms de Mexico as a major focus of the investigation.
The company voluntarily removed iceberg lettuce sourced from central Mexico from the U.S. market because of the potential for Cyclospora contamination, according to the FDA.
The FDA and CDC have worked with state and local health departments to trace illnesses and identify potentially affected products.
A Record-Breaking Year for Cyclospora Illnesses
The lettuce investigation comes as the United States is already experiencing an unusually high number of domestically acquired cyclosporiasis cases.
In a July 2026 health advisory, the CDC reported 1,645 confirmed domestic cases since May 1, compared with 249 cases during the same period in 2025.
More than 5,100 additional reports required further analysis at that time to determine whether they represented domestically acquired cyclosporiasis.
The CDC said the actual number of illnesses could be higher because cyclosporiasis is often underdiagnosed and underreported.
What Is Cyclosporiasis?
Cyclosporiasis is a gastrointestinal illness caused by the microscopic parasite Cyclospora cayetanensis.
People become infected when they consume food or water contaminated with the parasite.
Fresh fruits and vegetables have been associated with previous U.S. outbreaks, making produce safety an important part of the current investigation.
Unlike many bacterial foodborne illnesses, cyclosporiasis is caused by a parasite with a complex life cycle.
Symptoms Can Last for Weeks
The most common symptom is watery diarrhea, which can be frequent and sometimes severe.
Other symptoms can include:
- Loss of appetite
- Weight loss
- Stomach cramps
- Bloating
- Increased gas
- Nausea
- Fatigue
- Vomiting
- Body aches
- Headache
- Fever
Symptoms commonly begin about a week after exposure, although onset can occur between two and 14 days.
Without treatment, illness can follow a pattern of improving and returning and may last for weeks or longer.
Hospitalizations Have Been Reported
The outbreak has not been associated with reported deaths, according to the CDC’s July health advisory.
However, the illness can become serious.
Among the 1,645 confirmed domestic cases reported at that point, 141 people, or 9%, had been hospitalized.
That figure highlights why health officials are urging healthcare providers to consider Cyclospora when patients experience prolonged or recurring diarrhea.
Diagnosis Can Be Difficult
One of the challenges facing doctors is that Cyclospora can be difficult to identify through routine testing.
The CDC says standard ova-and-parasite examinations may not reliably detect the parasite.
Doctors who suspect cyclosporiasis may need to specifically request testing for Cyclospora.
That diagnostic challenge can contribute to delays in identifying cases and linking illnesses to a common food source.
The Outbreak Is Not the Only Source of Illness
Health officials are making an important distinction between the lettuce-linked outbreak and other cyclosporiasis cases.
The CDC says the iceberg lettuce outbreak was a major driver of the increase in cases this year, but investigators are also examining other outbreaks and illnesses that appear unrelated to the lettuce investigation.
That means the national case count should not automatically be attributed to a single food product.
Recalled Products Should Not Be Consumed
The FDA and CDC have advised consumers to avoid recalled products associated with the investigation.
The CDC says recalled food should not be eaten, even if it looks or smells normal.
Consumers should also monitor food-safety alerts as investigations develop.
Why Fresh Produce Can Be Difficult to Monitor
Leafy greens and other fresh produce create particular food-safety challenges.
They are often eaten raw, meaning there may be no cooking step to kill microorganisms or parasites before consumption.
Produce can also pass through multiple stages of harvesting, processing, packaging, distribution and food-service preparation.
Tracing contamination therefore requires cooperation across a complicated supply chain.
Washing Produce Helps, but Is Not a Guarantee
The CDC recommends washing raw fruits and vegetables thoroughly under running water before eating, cutting or cooking them.
However, washing cannot guarantee that Cyclospora will be removed.
The agency says cooking produce to at least 158°F (70°C) can kill the parasite.
For products intended to be eaten raw, consumers should follow current recall and food-safety guidance rather than relying solely on washing.
Food-Service Businesses Face Additional Pressure
Restaurants and other food-service businesses are also closely watching the investigation.
A contaminated ingredient can potentially be distributed across multiple locations before an outbreak is recognized.
That makes supplier records and traceability critical to quickly identifying affected products.
The initial FDA investigation specifically involved lettuce served at Taco Bell locations across several states.
Summer Is a Key Season for Cyclospora
The timing of the outbreak is also significant.
The CDC considers May 1 through August 31 the annual cyclosporiasis season in the United States.
Reported cases typically increase during spring and summer.
That seasonal pattern means health officials continue to monitor cases even as the summer season approaches its end.
The Investigation Could Take Time
Foodborne-outbreak investigations are rarely resolved overnight.
Health officials must compare patient interviews, laboratory results, food histories and distribution records.
They may also conduct traceback investigations to determine where contaminated products originated.
In the case of Cyclospora, the process can be especially challenging because symptoms may appear days after exposure and patients may not immediately remember everything they ate.
What Consumers Should Watch For
Consumers should pay attention to FDA and CDC food-safety announcements.
Anyone who develops persistent or recurring watery diarrhea should consider contacting a healthcare professional, particularly if they recently consumed fresh produce associated with an outbreak.
Patients should tell their healthcare provider about recent food consumption and travel history.
The CDC specifically recommends that clinicians ask patients with suspected or confirmed cyclosporiasis about recent food and travel exposures.
Treatment Is Available
Cyclosporiasis can be treated.
The CDC recommends trimethoprim-sulfamethoxazole, commonly known as TMP-SMX, for confirmed infections in immunocompetent adults and children older than two months, with treatment typically lasting seven to 10 days.
Patients should follow medical advice and focus on maintaining adequate hydration, particularly when diarrhea is frequent.
A Broader Food-Safety Warning
The lettuce outbreak is another reminder of the challenges involved in protecting America’s increasingly complex food supply.
Fresh produce can travel across borders and through multiple businesses before reaching consumers.
When contamination occurs, federal agencies must coordinate quickly with state health departments, restaurants, distributors and suppliers.
The Bottom Line
The U.S. response to the 2026 cyclosporiasis surge is expanding as federal investigators examine a multistate outbreak linked to iceberg lettuce and work to determine how the parasite entered the food supply.
The CDC says the lettuce-linked investigation involves 20 states, while other Cyclospora illnesses are being investigated separately.
The broader numbers are also significant.
The CDC reported 1,645 confirmed domestically acquired cases by July 14, substantially higher than the 249 reported during the comparable period the previous year.
For consumers, the most important steps are to monitor food recalls, avoid recalled products, wash fresh produce carefully and seek medical attention for persistent symptoms.
For healthcare providers, recognizing cyclosporiasis and requesting appropriate testing can help identify cases that might otherwise go undiagnosed.
For federal and state investigators, the priority remains identifying contaminated products, tracing their distribution and preventing additional illnesses.
The 2026 outbreak demonstrates how a microscopic parasite can create a nationwide food-safety challenge—and why rapid detection, supply-chain traceability and clear public-health communication remain essential to protecting American consumers.
Source angle: CDC cyclosporiasis surveillance, CDC multistate outbreak investigation, FDA food-safety investigation, iceberg lettuce recall, fresh-produce safety and 2026 domestic case data.
