FDA Raises a Listeria monocytogenes Outbreak in the United States to 50 Cases with No Food Identified

The U.S. Food and Drug Administration (FDA) updated its table of foodborne illness outbreak investigations in late October 2026. The Listeria monocytogenes outbreak with reference number 1417, which the agency added to the table on September 23, rises from 46 to 50 cases. The investigation is active, the outbreak is ongoing and the linked food is still listed as “not yet identified.”

It is one of two Listeria outbreaks the FDA has open with no known vehicle: the other, reference number 1415, was posted on September 30 with 11 cases. The agency explains that it only issues a public health advisory when the investigation allows it to give consumers concrete actions, and that it does not name a product until it has sufficient evidence that it caused the illnesses. In the meantime, it asks anyone who thinks they have a foodborne illness to see a doctor and report what they ate to health authorities.

Identifying the food in a listeriosis outbreak is especially difficult. The incubation period can last several weeks, so patients struggle to remember what they ate, and the bacterium is mainly associated with refrigerated ready-to-eat foods such as soft cheeses, deli meats, prepared salads and smoked seafood, in which it can multiply even in the cold. Invasive listeriosis is severe in pregnant women, newborns, older adults and immunocompromised people.

Until the vehicle is known, industry protection relies on environmental monitoring and lot-by-lot testing of ready-to-eat products. TAAG's Ampliora 2.3 kit detects Listeria spp. and L. monocytogenes by real-time PCR in food and in living and inert surfaces, in industries such as dairy, meat, ready-to-eat and seafood. The association with this outbreak is indirect as long as the FDA has not identified the food, and presumptive results must be confirmed with the reference method.