H5N1 bird flu found in four Southern California rats

The U.S. Department of Agriculture has added black rats to the growing list of mammals that have been infected by H5N1 bird flu.

The rats were located in Riverside County, and news reports suggest they were living in an area where two infected poultry farms had recently been identified.

The discovery of H5N1 in black rats — a typically urban species — provides another route for potential…