Investigation Details
Posted April 10, 2024
This outbreak is over. Learn what you can do to protect yourself from getting sick from Listeria.
CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) collected different types of data to investigate a multistate outbreak of Listeria monocytogenes infections.
Epidemiologic and laboratory data showed that queso fresco and cotija cheese made by Rizo-López Foods made people in this outbreak sick.
Epidemiologic Data
A total of 26 people infected with the outbreak strain of Listeria were 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 had been hospitalized. Two deaths were 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 were also two newborns with Listeria infections.
The true number of sick people in this outbreak was 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. In addition, recent illnesses may not yet have been reported as it usually takes 3 to 4 weeks to determine if a sick person is part of an outbreak.
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.
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 interviewed 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, four people reported eating brands made by Rio Lopez.
Laboratory Data
Public health investigators used the PulseNet system to identify illnesses that may have been 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 suggested 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 from two environmental samples that were collected at the facility.
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.
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.
