Bird flu virus circulated in cows for four months before outbreak confirmed by USDA, analysis shows
As agricultural authorities and epidemiologists try to get their arms around the scope of the latest confounding chapter in the decades-long story of the H5N1 avian influenza virus — its jump into U.S. herds of dairy cattle — they’re turning to the genetic breadcrumbs the virus leaves behind in the animals’ nose, lungs, and primarily, milk.
On Wednesday, U.S. Department of Agriculture scientists released a preprint — a study that has not yet been peer-reviewed — describing for the first time what their investigations of 220 viral genomes from infected cows have so far turned up. The study’s authors suggest that the spread in cattle started from a single spillover event from birds in the Texas panhandle that may have happened in early December. The USDA didn’t confirm the presence of H5N1 in a Texas herd until March 25.
