CDC, public health and regulatory officials in several states, the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS), 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 and laboratory data show that meat and cheese from deli counters contaminated with Listeria are making people sick. Investigators are still working to identify any specific products or delis that may be contaminated with the outbreak strain.
Epidemiologic Data
As of November 9, 2022, 16 people infected with the outbreak strain of Listeria have been reported from 6 states (see map). Sick people’s samples were collected from April 17, 2021, to September 29, 2022 (see timeline). The true number of sick people in this outbreak is likely higher than the number reported, and the 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 information about the age, ethnicity, and other demographics of sick people, and the types of foods they have eaten, to provide clues that can help identify the source of the outbreak. Sick people range in age from 38 to 92 years, with a median age of 74, and 62% are male. Of 13 people with ethnicity information available, 11 are of Eastern European background or speak Russian. Of 14 people with information available, 13 have been hospitalized, including one Maryland resident who died. One person got sick during their pregnancy, resulting in pregnancy loss.
State and local public health officials are interviewing people about the foods they ate in the month before they got sick. Of the 12 people interviewed, 11 reported eating meat or cheese from deli counters. Among seven sick people in New York, five bought sliced deli meat or cheese from at least one location of NetCost Market, a grocery store chain that sells international foods. Sick people from other states purchased deli meats or cheeses from other delis.
Investigators do not believe that NetCost Market delis are the only source of illnesses because some sick people in the outbreak did not shop at a NetCost Market. A contaminated food likely introduced the outbreak strain of Listeria into delis in multiple states.
Laboratory 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.
In 2021, health officials in New York state and New York City found the outbreak strain of Listeria in several environmental and food samples:
- Environmental samples from a NetCost Market deli in Brooklyn
- Several open packages of mortadella and ham that were sliced at the same NetCost Market deli in Brooklyn
- Sliced salami that a sick person bought from a NetCost Market deli in Staten Island
NetCost Market voluntarily closed the deli temporarily in Brooklyn after New York officials notified them about the sampling results. NetCost Market performed a deep cleaning and then reopened the deli in Brooklyn after further environmental testing did not identify Listeria.
In September 2022, the outbreak strain was found at the same Brooklyn NetCost Market deli; however, the most recent illness with NetCost Market exposure was in October 2021. After a deep cleaning, additional environmental testing did not identify Listeria in the deli.
Public Health Actions
CDC advises people at higher risk of severe Listeria illness to not eat meat or cheese from any deli counter, unless it is reheated to an internal temperature of 165°F or until steaming hot.
