In November 2015 samples of raw chocolate milk were collected from a raw milk conference held in Anaheim, California. The raw chocolate milk was produced by Miller's Organic Farm in Bird-In-Hand, Pennsylvania. The FDA isolated Listeria from the raw milk and conducted Whole Genome Sequencing (WGS) on the isolate. On January 29, 2016 FDA informed CDC that WGS determined that the Listeria bacteria from the raw chocolate milk was closely related genetically to Listeria bacteria isolated in two persons in the United States who got sick in 2014. One patient was from California. One patient was from Florida. Both ill persons were hospitalized. The ill person in Florida died.

Once the illnesses were identified in late January 2016, public health officials interviewed their family members about exposures prior to illness onset. It was reported that both ill people drank raw milk before they got sick. the family of the deceased person in Florida reported purchasing raw milk from Miller's Organic Farm.