2012 Salmonella Outbreak Linked to Ground Beef

Introduction

CDC collaborated with public health officials in many states and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) to investigate a multistate outbreak of Salmonella Enteritidis infections linked to ground beef produced on May 25, 2012 by Cargill Meat Solutions at a single production facility (EST. 9400). Public health investigators used DNA “fingerprints” of Salmonella bacteria obtained through diagnostic testing with pulsed-field gel electrophoresis (PFGE) to identify cases of illness that may be part of this outbreak. They used data from PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections.  Since the PFGE pattern of the outbreak strain is typically associated with 8 to 12 cases per month, Multiple-Locus Variable-number tandem repeat Analysis (MLVA) was used in addition to PFGE to define the outbreak strain.

A total of 46 individuals infected with the outbreak strain of Salmonella Enteritidis were reported from 9 states. The number of ill persons identified in each state was as follows: Maine (2), Massachusetts (3), New Hampshire (3), New York (20), North Carolina (1), Rhode Island (3), Vermont (11), Virginia (2), and West Virginia (1).

Among 46 persons for whom information was available, illness onset dates ranged from June 6, 2012 to July 27, 2012. Ill persons ranged in age from 3 years to 101 years, with a median age of 50 years; 54% were female. Among 36 persons with available information, 12 (33%) reported being hospitalized. No deaths were reported.

This particular outbreak appears to be over. While the use-by date of the recalled ground beef has passed, consumers might still have recalled ground beef in their homes if the ground beef was frozen at home. Consumers should check freezers for recalled ground beef products and should not eat them.

Investigation of the Outbreak

Epidemiologic, laboratory, and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies linked this outbreak to ground beef produced by Cargill Meat Solutions at a single production facility (EST. 9400).

In interviews, ill persons answered questions about foods consumed and other exposures during the week before becoming ill. By July 20, 2012, 26 (90%) of 29 ill persons interviewed reported consuming ground beef in the week before their illness began. This proportion is significantly higher when compared with results from a survey [PDF – 29 pages] of healthy persons, in which 69% of persons interviewed during the month of June reported consuming ground beef in the 7 days before they were interviewed. Among the 26 ill persons who reported consuming ground beef, 17 (65%) reported purchasing ground beef from various locations of the same grocery store chain. Among the 14 ill persons who remembered the type of ground beef, 9 (64%) recalled purchasing 85% lean ground beef.

Laboratory testing conducted by state public health laboratories isolated the outbreak strain of Salmonella Enteritidis from 2 unlabeled packages of leftover ground beef reportedly purchased from this grocery store chain and collected from 2 separate case-patient homes in New York and Vermont. Results of antibiotic susceptibility testing indicate that this strain of Salmonella is susceptible to commonly prescribed antibiotics.

Working in conjunction with the CDC, Vermont Department of Health, New York State Department of Health, and New York State Department of Agriculture & Markets, FSIS was able to link illnesses in five case-patients to ground beef products produced at a single Cargill Meat Solutions establishment (EST. 9400) based on epidemiologic and traceback investigations, as well as in-store reviews.

On July 22, 2012, Cargill Meat Solutions recalled 29,339 pounds of fresh ground beef products. The products subject to recall bear the establishment number “EST. 9400” inside the USDA mark of inspection. While the use-by date has passed and these products are no longer available for retail sale, FSIS and the company are concerned that some product may be frozen in consumers’ freezers. Consumers should not eat the recalled ground beef, and retailers and food service establishments should not serve it.

Salmonella is an important cause of human illness in the United States. More information about Salmonella infections, and steps people can take to reduce their risk of infection, can be found on the CDC Salmonella Web Page and the CDC Vital Signs Web Page.

September 13, 2012

Final Case Count Update

A total of 46 individuals infected with the outbreak strain of Salmonella Enteritidis were reported from 9 states. Since the last update, 6 new cases were reported from 4 states: Maine (1), New Hampshire (1), New York (2), North Carolina (1), and Rhode Island (1).

Among 46 persons for whom information was available, illness onset dates ranged from June 6, 2012 to July 27, 2012. Ill persons ranged in age from 3 years to 101 years, with a median age of 50 years; 54% were female. Among 36 persons with available information, 12 (33%) reported being hospitalized. No deaths were reported.

August, 6, 2012

Case Count Update

A total of 40 individuals infected with the outbreak strain of Salmonella Enteritidis have been reported from 8 states. The 7 new cases are from 4 states: New York (4), Rhode Island (1), Vermont (1), and West Virginia (1).

Among 40 persons for whom information is available, illness onset dates range from June 6, 2012 to July 9, 2012. Ill persons range in age from 3 years to 101 years, with a median age of 50 years; 53% are female. Among 33 persons with available information, 11 (33%) reported being hospitalized. No deaths have been reported.

Illnesses that occurred after July 10, 2012 might not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported.

Initial Announcement

July 23, 2012

CDC is collaborating with public health officials in many states and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS) to investigate a multistate outbreak of Salmonella Enteritidis infections. Public health investigators are using DNA “fingerprints” of Salmonella bacteria obtained through diagnostic testing with pulsed-field gel electrophoresis, or PFGE, to identify cases of illness that may be part of this outbreak. They are using data from PulseNet, the national subtyping network made up of state and local public health laboratories and federal food regulatory laboratories that performs molecular surveillance of foodborne infections.

A total of 33 individuals infected with the outbreak strain of Salmonella Enteritidis have been reported from 7 states. The number of ill people identified in each state with the outbreak strain is as follows: Maine (1), Massachusetts (3), New Hampshire (2), New York (14), Rhode Island (1), Virginia (2), and Vermont (10).

Among 33 persons for whom information is available, illness onset dates range from June 6, 2012 to June 26, 2012. Ill persons range in age from 12 years to 101 years, with a median age of 55 years; 55% are female. Among 30 persons with available information, 11 (37%) reported being hospitalized. No deaths have been reported.

The outbreak can be visually described with a chart showing the number of people who became ill each day. This chart is called an epidemic curve or epi curve. Since this PFGE pattern is typically associated with 8 to 12 cases per month, Multiple-Locus Variable-number tandem repeat Analysis (MLVA) is being used in addition to PFGE to define the outbreak strain. Illnesses that occurred after June 29, 2012 might not be reported yet 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 3 weeks. For more details, please see Salmonella Outbreak Investigations:Timeline for Reporting Cases.

Investigation of the Outbreak

Epidemiologic and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies indicate that ground beef is the likely source of this outbreak of Salmonella Enteritidis infections. In interviews, ill persons answered questions about foods consumed and other exposures during the week before becoming ill. Twenty-six (90%) of 29 ill persons interviewed reported consuming ground beef in the week before their illness began. This proportion is significantly higher when compared with results from a survey [PDF – 29 pages] of healthy persons, in which 69% of persons interviewed during the month of June reported consuming ground beef in the 7 days before they were interviewed. Among the 26 ill persons who reported consuming ground beef, 17 (65%) reported purchasing ground beef from various locations of the same grocery store chain. Among the 14 ill persons who remembered the type of ground beef, 9 (64%) recalled purchasing 85% lean ground beef.

Laboratory testing conducted by state public health laboratories isolated the outbreak strain of Salmonella Enteritidis from 2 unlabeled packages of leftover ground beef reportedly purchased from this grocery store chain and collected from 2 separate case-patient homes in New York and Vermont. Preliminary results of antibiotic susceptibility testing indicate that this strain of Salmonella is susceptible to commonly prescribed antibiotics.

Working in conjunction with the CDC, Vermont Department of Health, New York State Department of Health, and New York State Department of Agriculture & Markets, FSIS was able to link illnesses in five case-patients to ground beef products produced at a single Cargill Meat Solutions establishment (EST. 9400) based on epidemiologic and traceback investigations, as well as in-store reviews.

CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview ill persons about foods eaten before becoming ill. FSIS is continuing to work closely with CDC and state partners during this investigation. CDC will update the public on the progress of this investigation as information becomes available.

Recall

On July 22, 2012, Cargill Meat Solutions recalled 29,339 pounds of fresh ground beef products. The products subject to recall bear the establishment number “EST. 9400” inside the USDA mark of inspection. While the use-by date has passed and these products are no longer available for retail sale, FSIS and the company are concerned that some product may be frozen in consumers’ freezers.

It is important for consumers to note that the recalled products were repackaged into consumer-size packages and sold under different retail brand names and may not bear “EST. 9400” on the packaging, so consumers were advised to visit the FSIS site for a list of stores that sold these meat products. More information on recalled products can be found at: FSIS Recalls: Current Recalls & Alerts.