August 14, 2015
The Washington State Department of Health (DOH) and Public Health—Seattle & King County (SKC), with CDC and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS), are investigating an outbreak of Salmonella I 4,,12:i:- infections linked to pork.
Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet, the national subtyping network of public health and food regulatory agency laboratories, is coordinated by CDC. DNA “fingerprinting” is performed on Salmonella bacteria isolated from ill people by using a technique called pulsed-field gel electrophoresis, or PFGE. PulseNet manages a national database of these DNA “fingerprints” to identify possible outbreaks. Five DNA “fingerprints” (outbreak strains) are included in this outbreak investigation. The five strains are rare in Washington.
A total of 134 ill people infected with the outbreak strains of Salmonella I 4,,12:i:- have been reported from Washington.
Among people for whom information is available, illnesses started on dates ranging from April 25, 2015 to August 1, 2015. Ill people range in age from 1 year to 90, with a median age of 35. Forty-six percent of ill people are female. Among 111 ill people with available information, 16 (14%) report being hospitalized. No deaths have been reported.
This outbreak can be illustrated with a chart showing the number of people who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that occurred after July 27, 2015 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 4 weeks. Please see the Timeline for Reporting Cases of Salmonella Infection for more details.
Investigation of the Outbreak
CDC is assisting DOH and SKC with the epidemiologic investigation. A CDC Epi-Aid team arrived in Seattle, Washington on August 3, 2015.
Epidemiologic, laboratory, and traceback findings identified pork produced by Kapowsin Meats as a likely source of this outbreak of Salmonella I 4,,12:i:- infections. This investigation is ongoing.
In ongoing interviews, ill people answered questions about foods eaten and other exposures in the week before they became ill. Of 55 people for whom information is available, 37 (67%) reported eating pork in the week before becoming ill. This proportion was significantly higher than results from a survey [PDF – 29 pages] of healthy people in which 43% reported eating pork in the week before they were interviewed. In addition, numerous ill people were identified as part of illness clusters following events such as whole hog roasts. An illness cluster is defined as two or more people who do not live in the same household who report eating at the same restaurant location, attending a common event, or shopping at the same location of a grocery store in the week before becoming ill. Investigating illness clusters can provide critical clues about the source of an outbreak. If several unrelated ill persons ate or shopped at the same location of a restaurant or store within several days of each other, it suggests that the contaminated food item was served or sold there.
On July 31, 2015, USDA-FSIS issued a public health alert due to concerns about illnesses caused by Salmonella I 4,,12:i:- that may be associated with pork products, specifically whole pigs used for roasts. USDA-FSIS advises all consumers to safely prepare raw meat products and only consume pork products that have been cooked to an internal temperature of 145°F with 3 minutes of rest time.
Laboratory testing of environmental samples collected from Kapowsin Meats by DOH confirmed the outbreak strain was present in the facility. The business, which is regulated by USDA-FSIS, has cooperated with the investigation.
As a result of this investigation, on August 13, 2015, Kapowsin Meats voluntarily recalled approximately 116,262 pounds of whole pigs that may be contaminated with Salmonella I 4,,12:i:-. The product subject to recall bears the establishment number “est. 1628” inside the USDA mark of inspection and was produced on various dates between April 18, 2015 and July 27, 2015. The product was shipped to various individuals, retail locations, institutions, and distributors in Alaska and Washington.
The National Antimicrobial Resistance Monitoring System (NARMS) is a U.S. public health surveillance system that tracks antibiotic resistance in foodborne and other enteric bacteria found in people, raw meat and poultry, and food-producing animals. NARMS is a partnership among the CDC, the U.S. Food and Drug Administration (FDA), USDA, and state and local health departments.
The NARMS human surveillance program at CDC monitors antibiotic resistance in Salmonella and other bacteria isolated from clinical specimens submitted to NARMS by public health laboratories. CDC’s NARMS laboratory conducted antibiotic resistance testing on clinical isolates collected from three ill people infected with one of the outbreak strains. Of the three isolates tested, all (100%) were multidrug resistant. This included resistance to ampicillin, streptomycin, sulfisoxazole, and tetracycline. Antibiotic resistance may be associated with increased risk of hospitalization, development of a bloodstream infection, or treatment failure in patients. CDC’s NARMS laboratory continues to conduct antibiotic resistance testing on additional clinical isolates collected from ill persons infected with the outbreak strains. Results will be reported when they become available.
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.