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Investigation Details
Posted July 19, 2024
CDC, public health and regulatory officials in several states, and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are collecting different types of data to identify the food source of a multistate outbreak of Listeria monocytogenes infections.
Epidemiologic information shows that many people in this outbreak report eating meats sliced at deli counters. We do not have information to show that people are getting sick from prepackaged deli meats.
Epidemiologic Data
As of July 19, 2024, a total of 28 people infected with the outbreak strain of Listeria have been reported from 12 states (see map). Sick people’s samples were collected from May 29, 2024, to July 5, 2024 (see timeline). Of 28 people with information available, all have been hospitalized. One person got sick during their pregnancy and remained pregnant after recovering. Two deaths have been reported, 1 in Illinois and 1 in New Jersey.
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 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 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).
| Demographics | Information |
|---|---|
| Age (n=27) |
Range from 32 to 94 years Median age of 75 |
| Sex (n=28) |
46% female 54% male |
| Race (n=22) |
72% White 23% African American/Black 5% Asian |
| Ethnicity (n=22) |
96% non-Hispanic 4% Hispanic |
State and local public health officials are interviewing people about the foods they ate in the month before they got sick. People are reporting eating a variety of meats sliced at deli counters. Of the 18 people able to be interviewed, 16 (89%) reported eating meats sliced at a deli, most commonly deli-sliced turkey, liverwurst, and ham. Meats were sliced at a variety of supermarket and grocery store delis.
CDC conducted an analysis comparing foods reported by people in this outbreak to foods reported by people who got sick with Listeria but were not part of an outbreak. The analysis showed that people in this outbreak were more likely to eat deli-sliced turkey and liverwurst. This information suggests that meats sliced at the deli are a likely source of this outbreak. However, at this time CDC doesn’t have enough information to say which deli meats are the source of this 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 may have gotten sick from eating this food.
USDA-FSIS is working to identify the suppliers of deli meats, sliced at deli counters, purchased by people in this outbreak.
Public Health Actions
CDC advises people who are pregnant, aged 65 or older, or have a weakened immune system to contact their healthcare provider if they have any Listeria symptoms. Additionally, CDC advises people to take steps to protect themselves from getting Listeria from deli meats by avoiding eating meats sliced at the deli unless they are heated before eating.
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.
CDC investigated this outbreak in 2017 and 2021. Epidemiologic evidence in previous investigations identified queso fresco and other similar cheeses as a potential source of the outbreak, but there was not enough information to identify a specific brand. CDC reopened the investigation in January 2024 after new illnesses were reported in December 2023 and the outbreak strain was found in a cheese sample from Rizo-López Foods.
Epidemiology and recent laboratory data show that queso fresco and cotija made by Rizo-López Foods are making people in this outbreak sick.
Epidemiologic Data
As of February 6, 2024, a total of 26 people infected with the outbreak strain of Listeria have been reported from 11 states (see map). Illnesses started on dates ranging from June 15, 2014, to December 10, 2023 (see timeline). Of 26 people with information available, 23 have been hospitalized. Two deaths have been reported, one from California and one from Texas.
Among people who are pregnant, Listeria can cause pregnancy loss, premature birth, or a life-threatening infection in their newborn. In this outbreak, two people got sick during their pregnancy and one person had a pregnancy loss. There are also two newborns in the case count for this outbreak because Listeria can be passed to newborns during pregnancy.
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 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 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).
| Demographics | Information |
|---|---|
| Age (n=26) |
Range from <1 to 88 years Median age of 52 |
| Sex (n=26) |
58% female 42% male |
| Race (n=21) |
71% White 5% Native American or Alaska Native 24% reported another race category |
| Ethnicity (n=26) |
85% Hispanic 15% non-Hispanic |
State and local public health officials are interviewing people about the foods they ate in the month before they got sick. Of the 22 people interviewed, 16 (73%) reported eating queso fresco, cotija, or other similar cheeses. Among people who remembered specific brands, three people who got sick between 2014 and 2022 reported Don Francisco brand queso fresco or cotija. Don Francisco is one of the brands of recalled cheeses.
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 from 2014 to present are closely related genetically. This suggests that people in this outbreak got sick from the same food.
In January 2024, the Hawaii State Department of Health’s Food and Drug Branch collected a sample of aged cotija cheese product made by Rizo-López Foods during routine sampling. Testing identified the outbreak strain of Listeria in the product.
FDA conducted inspections at the Rizo-López Foods facility and collected food and environmental samples for testing. FDA found the outbreak strain of Listeria on a container where cheeses are kept before they are packaged.
Public Health Actions
On January 11, 2024, Rizo-López Foods, Inc. recalled the aged cotija cheese product after Hawaii state officials found Listeria in it.
On February 6, 2024, Rizo-López Foods, Inc. recalled all cheese and other dairy products made in their facility. They have also temporarily stopped producing and distributing these products while their investigation is ongoing.
Do not eat, sell, or serve any recalled products.
