Bird flu has been detected in rats for the first time, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service confirmed Wednesday.

Four black rats were confirmed to have H5N1 avian flu in late January in Riverside County, California, where two recent poultry outbreaks were reported, the agency said.

Officials have previously confirmed the virus in mice found on affected farms.

The agency's latest update also included other infected mammals in locations around the country, including a harbor seal in Massachusetts, a fox in North Dakota, a bobcat in Washington state and a domestic cat in Oregon. Officials said the cat infection is likely related to a recent report of two pets from Multnomah County that were sickened after eating raw pet food contaminated with the virus.

The latest bird flu discoveries come as the USDA is trying to rehire bird flu experts that the agency recently fired as part of cost-cutting based on recommendations from the Department of Government Efficiency, or DOGE.

"Although several positions supporting [highly pathogenic avian influenza] were notified of their terminations over the weekend, we are working to swiftly rectify the situation and rescind those letters," the USDA said in a statement to CBS News.

The agency said several types of workers, including veterinarians and other emergency response personnel, had been exempted from job cuts so that they could continue to work on the USDA's effort to deal with bird flu. The agency said it "continues to prioritize the response to highly pathogenic avian influenza (HPAI)."

Since the H5N1 strain of the bird flu began spreading in the U.S. in 2022, about 148 million birds on poultry farms have been euthanized to prevent additional infections, which has caused egg prices to spike. In March 2024, the illness was found in dairy cows for the first time, while almost 70 human cases have been identified, mostly in dairy and poultry workers. So far, one person, a Louisiana resident, has died from the virus.