Outbreak Investigation Updates by Date
Posted December 18, 2018 at 3:30 PM ET
This outbreak appears to be over. In general, people who are at higher risk for Listeria infection should avoid eating lunch meats, cold cuts, or other deli meats, unless they are heated to an internal temperature of 165°F or until steaming hot just before serving. Learn more about how you can take steps to prevent Listeria infection.
CDC and public health and regulatory officials in several states are investigating a multistate outbreak of Listeria monocytogenes infections. The U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS)External is monitoring this outbreak.
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 technique called whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. WGS performed on bacteria isolated from ill people showed that they were closely relatedly genetically. This means that people in this outbreak are more likely to share a common source of infection.
As of October 3, 2018, four people infected with the outbreak strain of Listeria monocytogenes have been reported from two 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 from ill people were collected from July 8, 2017, to August 11, 2018. Ill people range in age from 70 to 81 years, with a median age of 76 years. Fifty percent of ill people are female. All four ill people (100%) were hospitalized. One death has been reported from Virginia.
Illnesses that occurred after September 3, 2018, might not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 10 weeks. Please see the Timeline for Reporting Cases of Listeria Infection for more details.
Investigation of the Outbreak
Epidemiologic, laboratory, and traceback evidence indicates that deli ham from Johnston County Hams, Inc. in Smithfield, North Carolina is a likely source of the outbreak.
In interviews, ill people answered questions about the foods they ate and other exposures in the four weeks before they became ill. Three people were interviewed and all three (100%) reported eating deli ham or other deli meat from a grocery store or restaurant.
USDA-FSIS and state partners traced the source of the deli ham that ill people ate to Johnston County Hams, Inc. in Smithfield, North Carolina. The traceback investigation also showed Johnston County Hams products were served at an assisted living facility where the one ill person who could not be interviewed was a resident.
During routine inspections, federal regulatory officials collected deli ham from the Johnston County Hams, Inc. facility in 2016 and in early 2018. Whole genome sequencing results showed that Listeria identified in the deli ham in both years was closely related genetically to Listeria from ill people. These results provide more evidence that ill people became sick from eating contaminated deli ham.
On October 3, 2018, Johnston County Hams, Inc. recalled ready-to-eat deli ham products because they might be contaminated with Listeria bacteria. Recalled ham products were produced from April 3, 2017 through October 2, 2018. Return them to the store for a refund or throw them away. Restaurants and retailers should not serve or sell recalled Johnston County Hams products.
This investigation is ongoing, and CDC will provide updates when more information is available.