Four black rats in Riverside County, California have tested positive for H5N1 bird flu, marking the first confirmed rat cases in the United States since 2021. The infected rats were found near two previously identified infected poultry farms in the area.
The U.S. Department of Agriculture (USDA) has added black rats to the expanding list of mammals affected by the H5N1 virus. This discovery raises new concerns, as black rats typically inhabit urban areas and could potentially spread the virus between farms and residential areas through their droppings, urine, blood, and saliva.
The identification of H5N1 in rats adds to the growing list of affected North American mammals, which now includes over 50 species such as skunks, domestic cats, dolphins, seals, foxes, mountain lions, and coyotes. The virus has also impacted dairy cattle, with confirmed cases in 973 herds across 17 states.
Details about which agency conducted the initial testing of the rats remain unclear. When contacted, Riverside County's public health department redirected inquiries to the USDA, which has not provided additional information about the cases.
This development coincides with administrative challenges at the USDA, as the agency works to rehire bird flu scientists who were recently dismissed due to cost-cutting measures. The USDA has stated it is prioritizing its response to highly pathogenic avian influenza and is working to address staffing concerns, particularly for veterinarians and emergency response personnel focused on bird flu management.