H5N1 avian influenza continues to spread amid commercial and backyard poultry, and additional cases have been reported in domestic cats

California has also reported bird flu infections in cats fed raw milk or pet food. In one Los Angeles household, five cats got sick — and two died — after eating two kinds of raw pet food. Samples from one of the two brands, Monarch Raw Pet Food, tested positive for the virus, officials said.

"The Chinese poultry lineage may have experienced more vaccine-driven selection compared to other lineages," the researchers wrote.

New bird flu cases in animals including cats, bears and skunks are being detected across the country. Meanwhile the outbreak is leading to skyrocketing egg prices and shortages in stores. NBC’s Emilie Ikeda reports for TODAY.

According to the U.S. Bureau of Labor Statistics, the average price of a dozen grade A large eggs was $4.15 during the month of December—an increase from $2.51 in December 2023.