2019 Outbreak of Listeria Infections Linked to Unknown Source – Investigation Updates
Final Update
Posted November 7, 2019 at 1:00 PM ET
This outbreak appears to be over. CDC, several states, and federal partners investigated a multistate outbreak of Listeria monocytogenes infections. A single, common source of infections was not identified. Learn more about how you can take steps to prevent Listeria infection.
August 23, 2019
CDC, several states, and federal partners are investigating a multistate outbreak of Listeria monocytogenes infections. This investigation is ongoing and has not identified a specific food item, grocery store, or restaurant chain as the source of infections.
Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA fingerprinting is performed on Listeria bacteria isolated from ill people by using a standardized laboratory and data analysis method called whole genome sequencing (WGS). CDC PulseNet manages a national database of these sequences that are used to identify possible outbreaks. WGS gives investigators detailed information about the bacteria causing illness. In this investigation, WGS showed that bacteria isolated from ill people were closely related genetically. This means that people in this outbreak are more likely to share a common source of infection.
As of August 23, 2019, a total of 24 people infected with the outbreak strain of Listeria monocytogenes has been reported from 13 states. A list of the states and the number of cases in each can be found on the Map of Reported Cases page.
Listeria specimens were collected from ill people from July 20, 2017, to August 1, 2019. Ill people range in age from 35 to 92 years, with a median age of 72. Sixty-three percent of ill people are female. Of 23 ill people with information available, 22 hospitalizations have been reported. Two deaths have been reported.
The Public Health Agency of Canada is also investigating an outbreak of Listeria monocytogenes infections in several Canadian provinces linked to cooked diced chicken. Whole genome sequencing showed that the type of Listeria making people sick in Canada is closely related genetically to the Listeria making people sick in the United States.
This investigation is ongoing and a specific food item, grocery store, or restaurant chain has not been identified as the source of infections in the United States. State and local public health officials are interviewing ill people to determine what they ate and other exposures they had before their illness started. CDC will provide more information as it becomes available.
