The disclosure that dairy herds in Nevada have been infected by a version of the H5N1 bird flu not previously seen in cows has put virologists and researchers on high alert. Among other things, the news from the Nevada Department of Agriculture suggests that driving the virus out of the U.S. cattle population won’t be nearly as simple as federal officials once suggested—or perhaps hoped.
On Friday came a second and potentially more serious blow: A technical brief by the U.S. Department of Agriculture reported that the genotype, known as D1.1, contains a genetic mutation that may help the virus more easily copy itself in mammals—including humans.
