MINNEAPOLIS (AP) — The federal Centers for Disease Control and Prevention has reaffirmed the importance of properly cooking wild game after six people became sick from a parasite traced to undercooked bear meat that was served at a family reunion in South Dakota.

The six — one in South Dakota, four in Minnesota and one in Arizona — became infected when bear meat that was served rare turned out to be contaminated with roundworms that cause trichinellosis, also known as trichinosis. Two of the people ate only the vegetables that were grilled with the meat. While the meat had been frozen for 45 days, the trichinella worms were from a freeze-resistant species.

“Persons who consume meat from wild game animals should be aware that that adequate cooking is the only reliable way to kill Trichinella parasites and that infected meat can cross-contaminate other food,” the CDC said in its report on the outbreak last week.

The first case turned up after the 2022 reunion in a 29-year-old Minnesota man who had been hospitalized twice with fever, muscle aches and pain and swelling around his eyes, among other abnormalities. A sample of the meat, from a black bear harvested in Saskatchewan, tested positive. Three of the victims were hospitalized in all. All six, ranging in age from 12 to 62, eventually recovered.

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Trichinellosis has become rare in the U.S. While it was once commonly associated with undercooked pork, most U.S. cases nowadays are attributed to consumption of wild game. From 2016 to 2022, seven outbreaks, including 35 probable and confirmed cases, were reported to the CDC. Bear meat was the suspected or confirmed source in most of those outbreaks.

The larvae can settle into intestinal, muscle, heart and brain tissues, according to the National Institutes of Health. Most patients fully recover within two to six months.

The CDC recommends cooking wild game to at least 165 degrees Fahrenheit (74 degrees Celsius), as verified with a meat thermometer. Meat color is not a good indicator. The family members ate some of the meat before realizing it was undercooked and recooking it, the report said. Raw and undercooked meat and their juices should be kept separate from other foods.