Mexico investigates U.S. diarrhea outbreak linked to lettuce, denies contamination originated domestically

Mexico's Secretariat of Health is actively investigating a severe intestinal infection outbreak, cyclosporiasis, occurring in the United States. The investigation is prompted by indications that contaminated lettuce, possibly originating from Mexico, may be the source.

A traceability analysis conducted by Mexican authorities identified a single supplier of lettuce that served establishments involved in the outbreak. However, the Secretariat emphasized that pinpointing the country of origin for the product does not definitively confirm that the contamination began within Mexican territory. The investigation remains ongoing in coordination with U.S. health agencies.

U.S. health authorities have reported a significant number of cases linked to shredded iceberg lettuce served at a fast-food chain across various states. As of the latest reports, the outbreak is associated with 1,644 cases, 94 hospitalizations, and no fatalities. Symptoms began appearing between May 13 and July 13, 2026.

The Mexican inter-institutional technical group, comprising Cofepris, the General Directorate of Epidemiology, and the Ministry of Agriculture and Rural Development, is collaborating with the FDA. Their actions, including inspection visits and traceability analyses within Mexico, are primarily preventive and conducted under a continuous exchange of technical information to mitigate any potential health risks.

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According to the FDA, the traceability converges on a single supplier of lettuce that supplied the establishments involved. However, the investigation is ongoing, so it is important to specify that identifying the country of origin of the product constitutes a traceability data point, but does not in itself confirm that the contamination occurred in Mexican territory.