Connecticut, Maryland, New York and Virginia.
As of February 11, 2021, seven people infected with the outbreak strain of Listeria monocytogenes have been reported from four states. Illnesses started on dates ranging from October 20, 2020, to January 22, 2021, with six recent illnesses in 2021.
The true number of sick people in an 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 2 to 4 weeks to determine if a sick person is part of an outbreak.
Sick people range in age from 45 to 75 years, with a median age of 61. Six people are Hispanic, and 43% are female. All seven people have been hospitalized. No deaths have been reported.
State and local public health officials are interviewing people about the foods they ate in the month before they got sick. Of the four people interviewed, three reported eating at least one type of Hispanic-style fresh and soft cheeses and all three reported eating queso fresco. Public health officials are continuing to interview sick people to try to identify a specific type or brand of cheese.
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 means that people in this outbreak likely got sick from the same food.
State officials are testing samples of Hispanic-style fresh and soft cheeses that they collected from stores where sick people report purchasing cheeses from.