Investigation Update: Listeria outbreak, Deli Meat and Cheese - November 2022

March 29, 2023

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) investigated a multistate outbreak of Listeria monocytogenes infections.

Epidemiologic and laboratory data showed that meat and cheese from deli counters made people sick. A single deli or food source was not identified.

As of March 29, 2023, this outbreak is over.

Epidemiologic Data

A total of 16 people infected with the outbreak strain of Listeria were 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 have been limited to the states with known illnesses. This is because some people recover without medical care and are not tested for Listeria.

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

Sick people ranged in age from 38 to 92 years, with a median age of 74, and 62% were male. Of 15 people with race or ethnicity information available, 13 were White, 1 was African American/Black, 1 was Asian, and no one reported Hispanic ethnicity. Eleven people were of Eastern European background or spoke Russian.

Of 14 people with healthcare information available, 13 were hospitalized. One person got sick during their pregnancy, resulting in pregnancy loss. Additionally, one death was reported from Maryland.

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.

NetCost Market delis are unlikely to be 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 used the PulseNet system to identify illnesses that were 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 were 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 find 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 find Listeria in the deli.

Public Health Actions

Even when there are no ongoing outbreaks, CDC advises people at higher risk of Listeria illness to reheat deli meat and deli-sliced cheese to an internal temperature of 165°F or until steaming hot.