With Thanksgiving and turkey dinners just around the corner, food-safety investigators are still trying to pinpoint the source of drug-resistant salmonella that has shown up in some raw turkey around the country over the past year.

While more than 1 million Americans get sick from salmonella each year, this particular outbreak of drug-resistant salmonella has vexed experts because it is so diffuse, appearing in a variety of products and in most of the country.

The outbreak began shortly before Thanksgiving last year, but it has gotten relatively little attention because its source is unknown and there have been no product recalls.

The Centers for Disease Control and Prevention (CDC) said in an update last week that 164 people have been sickened by the strain, including 17 in Minnesota — the most of any U.S. state. There’s been one reported death, in California.

“Any type of antibiotic resistance is concerning,” said Sean Buuck, epidemiologist at the Minnesota Department of Health. But he noted that the list of antibiotics that the strain resists does not include some of the drugs that doctors most commonly use to treat a person with salmonella.

The CDC and the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) say that turkey is still safe to eat. But they also stress the importance of proper handling of raw turkey and thorough cooking.

Consumers should always wash their hands and all surface areas where the meat has been prepared. And turkey should be cooked and reheated to an internal temperature of 165 degrees Fahrenheit, the agencies said.

“No raw meat or poultry is sterile,” the FSIS said in a statement Thursday. “Consumers can protect themselves by cooking their turkey, other poultry products, and meat thoroughly. The cooking process kills the Salmonella. No one should be eating partially cooked or raw turkey.”

Cases of the drug-resistant salmonella have been surfacing at a slow but steady rate in multiple turkey products, including pet food, raw turkey products and live turkeys. It has been found in different brands, processing facilities and retailers in 35 states. Some turkey plant workers, including some in Minnesota, have become ill with the strain through contact with live birds.

The CDC and FSIS know of at least 22 slaughter facilities and seven processing plants where tainted product passed through, but the agencies have not released details.

“If FSIS had the ability to identify the source of this Salmonella strain, then the agency would immediately recall the items,” the agency said Thursday. “If we had specific products that we could alert consumers to with a Public Health Alert, we would issue one.”

Minnesota is the nation’s top turkey producing state, raising around 45 million birds a year. Two of the nation’s three largest turkey-producing companies, Hormel’s Jennie-O Turkey Store and Cargill, are based in Minnesota. Both referred questions to the National Turkey Federation. Joel Brandenberger, president of the federation, said turkey producers and processors are taking the outbreak seriously. “Food safety is not a competitive issue. When something like this happens, there is instant and immediate information shared between companies,” he said.

Ryan Osterholm, a Minneapolis attorney who is representing a 5-year-old Minnesota girl and several other people who have been severely sickened by the outbreak, said this is among the worst strains of salmonella he’s seen. “I try not to be an alarmist … but in my opinion, this is a major public health risk not being fully addressed by industry or the USDA,” he said.

The child he is representing developed osteomyelitis, a painful bone infection. She and at least one other sickened Minnesota child live in homes that fed their dogs raw pet food containing ground turkey, according to the Minnesota Department of Health.

“[My clients] were doing exactly what everyone else does with their turkey. They weren’t doing anything crazy,” Osterholm said. “But when it is this virulent, just a little can get you sick, even under the very best of preparation methods.”

Consumer Reports and the Center for Science in the Public Interest, a Washington, D.C.-based watchdog and consumer advocacy group, are urging the FSIS to release the names of the suppliers it has identified as being associated with products in the outbreak.

“When you are coming up on a major holiday where you know consumers are likely to consume the food in question, we think the agency has an obligation to give consumers whatever information it does have,” Laura MacCleery, CSPI’s policy director, said.

The FSIS rebuffed that idea Thursday. “It would be grossly irresponsible and reckless to associate producers with an outbreak investigation, when a link from an establishment to an illness has not been made,” the agency said.

“To be abundantly clear, FSIS has not identified a source or supplier of the product or products that are making consumers ill, but we continue to work around the clock with our federal and state public health partners to solve this,” it added.

Symptoms of salmonella include diarrhea, fever and stomach cramps and usually develop within 12 to 72 hours after exposure.