Investigation Announcement: Multistate Outbreak of Human Salmonella Heidelberg Infections

August 1, 2011

Introduction

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 Heidelberg infections that is likely caused by eating ground turkey. 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. The outbreak strain of Salmonella Heidelberg is resistant to many commonly prescribed antibiotics; this antibiotic resistance can increase the risk of hospitalization or possible treatment failure in infected individuals.

A total of 77 persons infected with the outbreak strain of Salmonella Heidelberg have been reported from 26 states between March 1 and August 1, 2011. The number of ill persons identified in each state is as follows:AL (1), AZ (2), CA (6), GA (1), IA (1), IL (7), IN (1), KY (2), LA (1), MA (1), MI (10), MN (1), MO (2), MS (1), NC (1), NE (2), NV (1), NY (2), OH (10), OK (1), OR (1), PA (5), SD (3), TN (2), TX (9), and WI (3).

Among persons for whom information is available, illnesses began on or after March 9, 2011. Ill persons range in age from less than 1 year to 88 years old, with a median age of 23 years old. Forty-eight percent are female.  Among the 58 ill persons with available information, 22 (38%) have been hospitalized. One death has 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 epi curve.  Illnesses that occurred after July 5, 2011, 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. Please see the Timeline for Reporting of Salmonella Cases for more details.

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Investigation of the Outbreak

Collaborative investigative efforts of state, local, and federal public health and regulatory agencies indicate that eating ground turkey is the likely source of this outbreak. Among the 51 ill persons with available information, 25 (49%) reported consuming ground turkey. This proportion is significantly higher than results from a survey of healthy persons in which 11% of persons of reported consuming ground turkey in the 7 days before they were interviewed. 

Cultures of four ground turkey samples purchased from four retail locations between March 7 and June 27, 2011 yielded Salmonella Heidelberg with the outbreak strain. Preliminary information indicates that three of these products originated from a common production establishment; the fourth is still under investigation. These were obtained as part of routine sampling in the National Antimicrobial Resistance Monitoring System (NARMS), and have not been linked to illnesses. Product information (such as date and location of purchase of ground turkey) is also being collected from ill persons and is being used by local, state, and federal public health, agriculture, and regulatory agencies to conduct traceback investigations.

On July 29, 2011 USDA-FSIS released a public health alert for frozen or fresh ground turkey products.  This alert reminds consumers of the critical importance of following package cooking instructions for frozen or fresh ground turkey products and general food safety guidelines when handling and preparing any raw meat or poultry. The alert advises that, in particular, while cooking instructions may give a specific number of minutes of cooking for each side of the patty in order to attain 165°F internal temperature, consumers should be aware that actual time may vary depending on the cooking method (broiling, frying, or grilling) and the temperature of the product (chilled versus frozen); therefore, it is important that the final temperature of 165 °F must be reached for safety.  The alert recommends that consumers not rely on the cooking time for each side of the patty, but use a food thermometer. For more information on this public health alert, please see FSIS Issues Public Health Alert for Frozen, Fresh Ground Turkey Products.

CDC, USDA-FSIS, and its public health partners are vigorously working to identify the specific contaminated product or products that are causing illnesses and will update the public on the progress of this investigation as information becomes available.  

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Clinical Features/Signs and Symptoms

Most persons infected with Salmonella bacteria develop diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. The illness usually lasts 4 to 7 days, and most persons recover without treatment. However, in some persons, the diarrhea may be so severe that the patient needs to be hospitalized. Salmonella infection may spread from the intestines to the bloodstream and then to other body sites and can cause death unless the person is treated promptly with antibiotics. Older adults, infants, and those with impaired immune systems are more likely to have a severe illness from Salmonella infection. More general information about Salmonella can be found here.

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Advice to Consumers, Retailers, and Others

• Wash hands, kitchen work surfaces, and utensils with soap and water immediately after they have been in contact with raw meat or poultry including frozen, fresh ground turkey. Then, disinfect the food contact surfaces using a freshly prepared solution of 1 tablespoon unscented liquid chlorine bleach to 1 gallon of water.
• Cook poultry thoroughly. Ground turkey and ground turkey dishes should always be cooked to 165 °F internal temperature as measured with a food thermometer; leftovers also should be reheated to 165 °F. The color of cooked poultry is not always a sure sign of its safety. Only by using a food thermometer can one accurately determine that poultry has reached a safe minimum internal temperature of 165 °F throughout the product. Turkey can remain pink even after cooking to a safe minimum internal temperature of 165 °F. The meat of smoked turkey is always pink. Be particularly careful with foods prepared for infants, older adults, and persons with impaired immune systems. For more information, please visit FoodSafety.gov.
• If served undercooked poultry in a restaurant, send it back to the kitchen for further cooking.
• Cross-contamination of foods should be avoided. Uncooked meats should be kept separate from produce, cooked foods, and ready-to-eat foods. Hands, cutting boards, counters, knives, and other utensils should be washed thoroughly after touching uncooked foods. Hands should be washed before handling food, and between handling different food items.
• Refrigerate raw and cooked meat and poultry within 2 hours after purchase (one hour if temperatures exceed 90° F). Refrigerate cooked meat and poultry within two hours after cooking. Refrigerators should be set to maintain a temperature of 40 °F or below.
• Persons who think they might have become ill from eating possibly contaminated ground turkey should consult their health care providers. Infants, older adults, and persons with impaired immune systems are more likely than others to develop severe illness.

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CDC's Role in Food Safety

CDC leads federal efforts to gather data on foodborne illnesses, investigate foodborne illnesses and outbreaks, and monitor the effectiveness of prevention and control efforts. CDC is not a food safety regulatory agency but works closely with the food safety regulatory agencies, in particular, with the U.S. Food and Drug Administration and USDA-FSIS. CDC also plays a key role in building state and local health department epidemiology, laboratory, and environmental health capacity to support foodborne disease surveillance and outbreak response. Notably, CDC data can be used to help document the effectiveness of regulatory interventions.

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