On August 23, 2019 the CDC announced an investigation of an outbreak of Listeria monocytogenes infections. At the time of the investigation notice, a total of 24 people infected with the outbreak strain had been reported by 13 states. Twenty two people had been hospitalized. Two people had died. Listeria specimens were collected from ill people from July 2017 to August 1, 2019. At the time of the announcement a specific food item, grocery store or restaurant chain had not been identified. On November 7, 2019 the CDC declared the outbreak to be over. The source remained a mystery.

The Public Health Agency of Canada (PHAC) also announced an outbreak of Listeria infections linked to cooked diced chicken. Whole genome sequencing showed that the type of Listeria making people sick in Canadian provinces was closely related genetically to the Listeria making people sick in the United States.