Outbreak Investigation Updates by Date

Published on November 19, 2019 at 12:15 PM ET

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November 1, 2019

CDC, public health and regulatory officials in several states, and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) are investigating a multistate outbreak of Salmonella Dublin infections linked to ground beef.

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 Salmonella 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 November 1, 2019, a total of 10 people infected with the outbreak strain of Salmonella Dublin have been reported from 6 states. A list of the states and the number of cases in each can be found on the Map of Reported Cases page.

Illnesses started on dates ranging from August 8, 2019, to September 22, 2019. Ill people range in age from 48 to 74 years, with a median age of 68. Eighty percent of ill people are male. Of nine ill people with information available, eight (89%) were hospitalized, and one death has been reported in California. In five (50%) ill people, Salmonella was found in samples of blood, which indicates their illnesses may have been more severe. Salmonella Dublin is known to commonly cause more severe illnesses than other Salmonella strains, particularly in older people.

Illnesses might not yet be reported due to the time it takes between when someone becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks. Please see the Timeline for Reporting Cases of Salmonella Infection for more details.

Whole genome sequencing analysis did not identify any antibiotic resistance in 16 bacterial isolates from 10 ill people and 6 food specimens. Testing of clinical isolates using standard antibiotic susceptibility testing methods by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) is underway.

Investigation of the Outbreak

Epidemiologic and laboratory evidence indicates that ground beef might be contaminated with Salmonella Dublin and is making people sick. At this time, the investigation has not identified a single, common supplier of ground beef.

In interviews, ill people answered questions about the foods they ate and other exposures in the week before they became ill. Of eight people interviewed, six (75%) reported eating ground beef at home. This percentage is significantly higher than results from a survey pdf icon[PDF – 787 KB] of healthy people in which 40% of respondents reported eating any ground beef at home in the week before they were interviewed. Ill people reported buying ground beef from various stores.

Laboratory testing identified the outbreak strain of Salmonella Dublin in repackaged leftover ground beef collected from an ill person’s home in California. The outbreak strain of Salmonella Dublin has also been identified in six samples of raw beef products from slaughter and processing establishments. Samples from slaughter and processing establishments were collected as part of FSIS’s routine testing under the Salmonella performance standards. WGS showed that the Salmonella strain from these samples was closely related genetically to the Salmonella from ill people. These results provide more evidence that people in this outbreak got sick from eating ground beef. At this time, the investigation has not identified a single, common supplier of ground beef.

This outbreak investigation is ongoing and CDC will update the public if more information becomes available.