In April 2023, the Utah Department of Health (UT DOH) and Salt Lake County Health Department (SLCoHD) investigated an outbreak of Salmonella related to a local market. On April 5, 2023, UT DOH was informed of an outbreak of gastrointestinal (GI) illness among a large group that purchased at least two cooked, ready-to-eat, whole pigs from Kim Thanh Marketplace, located at 3825 S Redwood Rd., West Valley City, Utah on April 2, 2023, and ate them for lunch that same day.
In total, 15 individuals associated with the family group outbreak were reported. Seven individuals sought medical care, of which three were reported to UT DOH with Salmonella through routine surveillance. At least one individual sought medical care for febrile seizures, although their stool cultures were negative for Salmonella and other enteric pathogens. All onsets occurred on April 3 and 4, 2023, except for one individual with an onset on April 10, 2023, who was likely a secondary case. Age data was available for nine individuals; the ages of cases ranged from 4 to 55 years.
Whole genome sequencing (WGS) conducted as part of routine surveillance identified the three lab-confirmed cases as serotype Salmonella I 4:i:- and closely related (within 0-2 SNPs) to each other. These cases were also closely related (within 12-14 SNPs) to a raw ground pork isolate collected by USDA-FSIS in Michigan in April 2022. The Utah Department of Agriculture and Food (UDAF) tested leftover pork from Kim Thanh Marketplace, which resulted positive for Salmonella on April 20, 2023. A total of 5 isolates from these samples were serotyped as Salmonella I 4:i:- at the Utah Public Health Laboratory (UPHL). These pork isolates are closely related (within 0-3 SNPs) to isolates from the three lab-confirmed cases.
On April 28, 2023, an environmental assessment was conducted at Kim Thanh Marketplace. No employees then reported any recent GI illness. Investigators were unable to observe the pig roasting process since no orders were being fulfilled at the time. However, investigators learned that the initial preparation step involves hanging the pig on a rack and splashing hot water on it before partially cooking the pig and placing it back in the walk-in cooler with other raw meat. To finish cooking the pig, the owner reportedly places the pig in the oven and cooks until it reaches a temperature of 170°F. The owner then turns the oven temperature down and hot-holds the pig until it is picked up by the customer.
While the owner says the pork is cooked to 170°F, investigators discovered that only two thermometers were in the establishment; one thermometer was broken, and the other still had the sticker on it, indicating that it was brand new and did not appear to have ever been used. The owner also made comments about using the color of the pig to determine if it was done cooking (i.e., kept cooking if the pig still looked pink). Another major concern was that raw meat and other food items were being held in the walk-in cooler at 50°F, a temperature warm enough to still allow proliferation of Salmonella and other pathogenic bacteria. A lack of sanitation was also identified; the only sanitizer found in the establishment was an empty bottle of Clorox bleach. Additionally, cockroaches were found in the kitchen area.
A total of 32 environmental samples were taken from the facility. Only one environmental swab (from a shopping cart) was presumptively positive for Salmonella. However, Salmonella never grew in culture. The owner also provided investigators with contact information for other customers who ordered roast pigs the weekend of April 1, 2023. SLCoHD attempted to contact these customers for case finding purposes but was unsuccessful. Invoices were also collected by investigators, showing that the source of the whole pigs was Tooele Valley Meats.
Salmonella-positive isolates from the leftover pork samples closely related to clinical samples from the family which confirms that the whole roast pig was the food vehicle in this outbreak. Investigators suspect the roast pig was undercooked; family members reported that the roast pig was room temperature upon pick-up. Additionally, observations regarding available thermometers in the establishment support this hypothesis.