The outbreak that has spread in the United States has killed 19,000 people: the cause remains unknown.

The food‑borne health crisis that has been raging in the United States for months and is recorded as the largest Cyclospora outbreak in the country's history is coming to an end. Federal officials are reportedly preparing to announce that the outbreak, which has seen more than 19,500 confirmed cases, has ended. However, the source of thousands of cases still remains a mystery.

More Than 19,500 Cases

Since May 1, more than 19,500 Cyclospora infections confirmed by laboratories across the United States have been reported. Health officials say the true case count could be much higher because many people neither get tested nor seek care.

The outbreak has claimed at least two lives in Michigan, and hundreds of people nationwide have been hospitalized. The worst Cyclospora season recorded in the United States before 2026 occurred in 2019, with about 4,700 cases identified.

Suspicions Turned to Fragmented Marula

As investigations progressed, a significant portion of cases was linked to fragmented iceberg lettuce processed by Taylor Farms in Mexico. According to CDC data, the outbreak cluster associated with these products sickened 11,458 people in 20 states, and the two deaths in Michigan were also linked to that cluster.

In the early stages of the investigation, many people who fell ill reported eating at Taco Bell restaurants, which helped investigators narrow down the possible source. The widespread use of the products in restaurant and food supply chains emerged as a significant factor in the spread of the outbreak.

However, No Definitive Source Found.

One of the most striking aspects of the outbreak is that the investigations have still failed to reach a definitive conclusion. Although epidemiological data and backtracking of the supply chain of the products strongly point to lettuce, scientists have not identified a lettuce sample that tested positive for Cyclospora.

Moreover, federal health agencies investigated thousands of other cases with no link to lettuce. In a significant portion of these cases, a definitive source of infection could not be identified. According to experts, the source of some cases may never be discovered.

What is Cyclospora?

Cyclospora is a microscopic parasite that can infect humans through contaminated food or water. The parasite that causes the intestinal disease known as "Cyclosporiasis" can lead to symptoms such as severe diarrhea, abdominal cramps, nausea, and fatigue.

Past outbreaks in the United States have been linked to lettuce and other leafy greens as well as fresh products such as cilantro and various fruits. Removing the parasite from the products by washing alone can also be difficult. Although heat can inactivate the parasite, many of the fresh items associated with the outbreaks are consumed raw.

Is Lettuce Safe to Eat Right Now?

According to health officials, consumers do not need to stay completely away from lettuce at this stage. The last-use dates of the recalled products linked to the outbreak have passed, and those items should no longer be found in stores or restaurants.

However, experts say that washing fruits and vegetables can reduce dirt and some bacteria, but it does not guarantee the complete elimination of Cyclospora. In cooked vegetables, the risk is considered lower because heat inactivates many pathogens.

The Outbreak Could Bite, Questions Remain

Under months-long investigations by federal agencies, product shipments were examined, patients were interviewed, and facilities in the United States and Mexico were inspected. The findings revealed a strong link between the largest cluster of cases and shredded iceberg lettuce, yet the outbreak's remaining unknowns could not be resolved.

After the drop in new case numbers, the announcement that the outbreak has officially ended is expected. However, this decision will not mean that all the mysteries of the health crisis have been solved. Because some cases can still be recorded even weeks after contaminated food has been removed from the market, due to late onset of symptoms and reporting processes.