CDC and several states are investigating an outbreak of Listeria monocytogenes infections (listeriosis). Listeria can cause a serious, life-threatening illness.
Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet, coordinated by CDC, is the national subtyping network of public health and food regulatory agency laboratories. PulseNet performs DNA fingerprinting on Listeria bacteria isolated from ill people by using techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks.
Investigation of the Outbreak
Collaborative investigative efforts of state, local, and federal public health and regulatory officials indicate that raw milk produced by Miller’s Organic Farm in Bird-In-Hand, Pennsylvania is the likely source of this outbreak. Raw milk is milk from cows or other animals that has not been pasteurized to kill harmful bacteria. This raw, unpasteurized milk can carry dangerous bacteria such as Listeria, Salmonella, E. coli, and Campylobacter, which are responsible for causing numerous foodborne illnesses and outbreaks.
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. The U.S. Food and Drug Administration (FDA) isolated Listeria from the raw chocolate milk and conducted WGS testing on the isolate to get more genetic information about the bacteria. 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 from two people in two states who got sick in 2014, one from California and one from Florida.
The age of ill people from California and Florida ranged from 73 to 81 years. Both ill people were hospitalized, and the ill person from Florida died as a result of listeriosis.
Once the two illnesses were identified in late January, public health officials worked over several weeks to interview them or their family members about the foods they may have eaten and other exposures in the month before their illness started. Interviews were conducted with the ill person from California and family members for both ill people. 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.
Raw milk and raw dairy products can pose severe health risks, including death, especially for people at higher risk for foodborne illness, including children younger than 5, pregnant women, adults 65 and older, and people with weakened immune systems. We recommend that people drink and eat only pasteurized dairy products. Learn more about the dangers of drinking raw milk at the CDC Food Safety and Raw Milk website.
Because Listeria was recently found in raw milk produced by Miller’s Organic Farm, we are concerned that contaminated raw milk and other raw dairy products from this company could still be on the market and make people sick.
This investigation is ongoing. CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them. Updates will be provided when more information is available.