Ten Cases From One Meal: Trichinellosis and Undercooked Bear Meat in North Carolina

Trichinellosis used to be a disease of pork. Changes in how pigs are raised made it rare in the United States, and most recent cases now come from wild game. In November 2023, a single gathering in western North Carolina where undercooked bear meat was served produced 10 probable cases — six of them in people aged 18 or younger.

How the disease works

Trichinella species are roundworms with a complex life cycle. People are infected by eating raw or undercooked meat that carries dormant larvae. Nationally, myalgia (muscle pain) and fever appear in 54% of cases and facial swelling in 42%; 0.2% of cases are fatal, and severe infection can also leave lasting muscle pain. That is why identifying cases quickly matters.

The outbreak

On November 29, 2023, the North Carolina Division of Public Health was alerted to a suspected case: a patient with flu-like illness and facial swelling. Investigators linked the patient to a gathering in early November where undercooked bear meat was served.

Among the 10 patients, nine had facial swelling, six had myalgia and four had a documented fever.

Days from the bear meat meal to symptom onset among the 10 probable cases, North Carolina, November 2023. CDC.

Why the cases stayed "probable"

The cases were classified on clinical and epidemiologic grounds — symptoms consistent with the 2014 Council of State and Territorial Epidemiologists definition, after eating the implicated meat. Laboratory proof was out of reach:

• Five patients were tested for Trichinella antibodies (IgG), and all were negative — but confirmation needs a second, convalescent blood sample, and none of them came back for one. By then symptoms have often resolved, and a recovered patient has little reason to return.
• No bear meat was left to test.

Treatment had its own problems. Most people with symptoms were prescribed the antiparasitic drug albendazole, but some started it late, and several said the cost — about $100 a course — was prohibitive.

Why bears

Black bears are common hosts of Trichinella, and thousands of bears are harvested each year in North Carolina. The report suggests new surveys of how often wild game species carry the parasite. It is not the first bear-meat outbreak: in 2022, undercooked bear meat harvested in Canada caused six cases, including two people who ate only vegetables — infected by cross-contamination.

How to prevent it

• Cook wild game meat to an internal temperature of at least 165°F (74°C). That kills Trichinella.
• Do not rely on freezing, which might not be enough.
• Keep raw game away from other food, as the 2022 outbreak showed.

Because diagnosis is hard and treatment can be costly and slow, the report concludes that the most effective prevention is for health departments and wildlife managers to spread the word on preparing wild game safely.

Sources

Based on Gowler CD, Lee N, Morrison T, Mears V, Williams C, Fleischauer A, Wilson E, "Notes from the Field: Suspected Outbreak of Trichinellosis Associated with Undercooked Bear Meat — North Carolina, November 2023," MMWR Morbidity and Mortality Weekly Report 2024;73(40), Centers for Disease Control and Prevention and the North Carolina Department of Health and Human Services; a work of the United States government in the public domain.