Investigation Update: Listeria Outbreak, June 2026

CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) are collecting different types of data to investigate a multistate outbreak of Listeria monocytogenes infections.

Epidemiologic, laboratory, and traceback data show that some requesón/soft ricotta cheese are contaminated with Listeria monocytogenes and are making people sick. The investigation is ongoing to determine the source of contamination and whether additional cheeses are linked to the outbreak.

Epidemiologic Data

As of June 4, 2026, a total of 8 people infected with the outbreak strain of Listeria have been reported from 3 states. Sick people's samples were collected on dates ranging from March 6, 2023, to May 9, 2026. Of 8 people with information available, 7 have been hospitalized and 1 death has been reported from Maryland.

The true number of sick people in this outbreak is likely higher than the number reported, and this outbreak may not be limited to the states with known illnesses. This is because some people recover without medical care and are not tested for Listeria. In addition, recent illnesses may not yet be reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak.

Public health officials collect many different types of information from sick people, including their age, race, ethnicity, other demographic characteristics, and the foods they ate in the month before they got sick. This information provides clues to help investigators identify the source of the outbreak.

The table below has information about sick people in this outbreak ("n" is the number of people with information available for each demographic).

State and local public health officials are interviewing people about the foods they ate in the month before they got sick. Of the 7 people interviewed, 5 reported eating any cheese. Two people reported eating requesón cheese made by Clover Hill Dairy. Other people reported exposures to different types of cheeses. The investigation is ongoing to determine if those cheese exposures relate to Clover Hill Dairy.

Public health investigators continue to gather information on what people ate before getting sick to determine whether additional products are linked to the outbreak.

Laboratory and Traceback Data

Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. CDC PulseNet manages a national database of DNA fingerprints of bacteria that cause foodborne illnesses. DNA fingerprinting is performed on bacteria using a method called whole genome sequencing (WGS). WGS showed that bacteria from sick people's samples are closely related genetically. This suggests that people in this outbreak got sick from the same food.

New York State Department of Agriculture and Markets (NYS AGM) collected samples at a retail location shopped at by sick people. One sample of requesón that was repackaged at this retailer tested positive for Listeria monocytogenes. WGS confirmed the Listeria in this cheese is the same as the Listeria making people sick in this outbreak.

NYS AGM also went to the distributor who supplied cheese to the retail location. They collected a sample from an unopened 18-pound bucket of requesón that was supplied by Clover Hill Dairy. This sample tested positive for Listeria monocytogenes. WGS is pending to see if it is the same strain as the strain that is making people sick in this outbreak.

Due to the public health risk, the Maryland Department of Health has suspended Clover Hill Dairy's operating license and is conducting a follow up evaluation in cooperation with the facility.

FDA's traceback investigation is ongoing.