The week after the November 2024 report, public health officials identified and interviewed 6 persons who consumed the bear jerky. We used the 2014 case definition from the Council for State and Territorial Epidemiologists (4) for case classification. We defined probable cases as the presence of clinically compatible symptoms in a person who shared an epidemiologically implicated meal or ate a meat product in which the parasite was found. We defined confirmed cases as the presence of clinically compatible symptoms with a positive laboratory test such as Trichinella antibody screening. Clinically compatible signs and symptoms included fever, myalgia, periorbital edema, and eosinophilia. This activity was reviewed by the Centers for Disease Control and Prevention (CDC), was deemed not research, and was conducted consistent with applicable federal law and CDC policy.

The bear was hunted in Graham County in western North Carolina at the start of bear season (October). Approximately half the meat was frozen as various cuts and half was prepared as jerky without prior freezing. Because the process involved only marination and dehydration, the jerky preparation likely did not reach the suggested >165°F (>74°C) internal temperature necessary to kill Trichinella spp. parasites. At the time of notification, purportedly no jerky remained, but 4 remaining frozen meat pieces were sent for testing at the CDC’s Division of Parasitic Diseases and Malaria, National Center for Emerging and Zoonotic Infectious Diseases.

The implicated bear jerky was shared among 6 persons. Trichinellosis symptoms developed in 3 persons, including 1 who was hospitalized with severe symptoms characteristic of trichinellosis: periorbital edema, eosinophilia, and muscle weakness. The patient’s physician had read of an outbreak of trichinellosis in western North Carolina reported in Morbidity and Mortality Weekly Report (3) and informed NCDPH. Public health officials advised those involved to cease further jerky consumption. State wildlife officials emailed a notice to a listserv of registered hunters about proper handling and cooking of bear meat.

The overall attack rate was 50% (n = 3), including probable cases in persons who ate the implicated meal and reported symptoms (Table 1). For confirmed cases only, the attack rate was 16% (n = 1). Median incubation period for symptomatic cases was 33 (range 27−40) days. The hospitalized patient was tested for Trichinella IgG twice. The first results were negative (collected 12 days after symptom development), but convalescent serum results (collected 31 days after symptom development) were positive (Table 2). Public health officials advised the remaining symptomatic persons of the value of testing, including convalescent testing, because of potential early false negatives. However, because they did not have health insurance, both were discouraged by the high cost (>$200) of testing. All symptomatic persons were treated with albendazole and recovered (Table 1).

CDC’s Division of Parasitic Diseases and Malaria tested 4 bear meat specimens. The meat was frozen at an unknown temperature for >57 days. Testing found encapsulated Trichinella spp. larvae in all 4 specimens; the parasite loads ranged from 18.6 to 47.9 larvae/g (Figure; Table 3). Two specimens contained a few larvae with very slight motility. Molecular testing using real-time PCR targeting the encapsulated North American Trichinella spp. identified the larvae as T. spiralis nematodes (Table 3).

We describe a trichinellosis outbreak in western North Carolina, providing additional evidence of changing trichinellosis patterns. Trichinellosis was rarely reported in North Carolina until 2023, when a probable outbreak of trichinellosis resulted in 10 symptomatic cases (3). However, the causative Trichinella species could not be determined. In the outbreak described in this article, T. spiralis nematodes were identified from leftover meat. This finding was somewhat unexpected because T. spiralis infection is rarely reported from bear meat, compared with rates for other Trichinella spp.(6). Wildlife disease surveillance is needed to update our knowledge of Trichinella prevalence, host affinities, and associated public health risks.

The outbreak we report also underscores the need for prevention to avoid painful, debilitating infections. Despite the risk for severe disease from trichinellosis, including persistent myalgia or even death, persons preparing wild game and other potentially affected meats for consumption still neglect to follow the recommended cooking measures. Furthermore, provider awareness of trichinellosis can help enable appropriate treatment and guide public health action. Treatment of trichinellosis is typically with albendazole or mebendazole and can be supplemented with steroid drugs for severe cases (7).

Trichinellosis is rare in the United States. The disease was once mostly associated with pork, but changes in husbandry practices coincided with a decrease in trichinellosis cases domestically (8). More recently, the few cases reported each year are mostly associated with consumption of wild game meat (8), with bear meat being the suspected or confirmed food source for recently reported outbreaks in the United States (9). The trichinellosis outbreak reported in this article and the 2023 probable outbreak in North Carolina (3) were both linked to undercooked bear meat harvested in-state. An increasing number of bears are harvested each year in North Carolina; ≈1,500 were harvested in 2023 (10). In the United States and Canada, human trichinellosis outbreaks associated with bear meat are more commonly attributed to infection with T. nativa nematodes (9,11), whereas contemporary outbreaks of T. spiralis infection are mostly associated with consumption of wild boar (6). A report from 2003 suggested that 2 T. nativa trichinellosis cases in Tennessee occurred because of a bear hunted in Canada (11), rather than in the southeastern United States. In Canada, polar bears and grizzly bears have been confirmed to carry Trichinella spp. nematodes (6).

Trichinellosis outbreaks associated with jerky prepared from bear (12) and other wild game (13) have been reported previously. In the outbreak described in this article, jerky preparation consisted of marinade and drying steps that likely did not reach sufficient temperatures for safe consumption. Freezing wild game meat before jerky preparation is sometimes recommended as a treatment step (https://nchfp.uga.edu) but might not be sufficient for killing freeze-resistant Trichinella spp. nematodes, such as T. nativa (7,9). Although T. spiralis nematodes are usually considered freeze-susceptible, experimental infection trials have demonstrated persistent larval motility after several weeks of freezing, albeit with declining infectivity over time (14). The weak motility noted in larvae from this report is not evidence of persistent infectivity after freezing, but because of the uncertainties and potential diversity of Trichinella in bear meat, freezing alone cannot be assumed to reliably eliminate infection risk. Cooking meat to an internal temperature >165°F (>74°C) verified by a meat thermometer remains the best method for killing all Trichinella species across different types of meat. Safe food handling practices, such as processing raw or undercooked meat separately from other foods, can prevent trichinellosis spread by cross-contamination (9,15).

Trichinellosis symptoms can be severe, and diagnosis can be challenging. Serologic testing for Trichinella IgG is often used to diagnose trichinellosis; however, IgG seroconversion might not be detectable until weeks after infection, potentially causing false negatives if serum is collected during acute infection. Convalescent serum samples are crucial for diagnostic and public health purposes, but their acquisition remains challenging. In addition, healthcare visits, diagnostic tests, and treatment are more difficult for uninsured patients, as demonstrated by the 2 symptomatic patients who did not receive testing during this outbreak.

In conclusion, we report an outbreak of trichinellosis in North Carolina that resulted from undercooked, locally harvested bear prepared as jerky, providing evidence of changing trichinellosis patterns. Low-cost safety measures can help prevent illness, and communication of disease prevention through safe wild game preparation is critical to avoid future outbreaks.