Analysis Suggests H5N1 D1.1 Genotype May Have Jumped to Nevada Cows Weeks Before Detection

By Lisa Schnirring

In new findings regarding the recent detection of the D1.1 H5N1 avian flu genotype in Nevada dairy cattle, an international team of virologists today reported that the jump from birds to dairy cattle may have occurred in early December, more than a month before quarantines were placed on two affected farms following detection through the national milk testing stem. 

The investigators published an analysis of viruses from four D1.1 bovine cases from a Nevada herd on Virological, an online hub for prepublication data designed to assist with public health activities and research. The study has not yet been peer-reviewed.

The four cattle D1.1 genomes were shared by the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS). The team said their analysis suggests all four came from a single herd, and they said more studies are needed to gauge the diversity of D1.1 in cattle.

Detection of the virus in Nevada cows supports the key role of the National Milk Testing Strategy, but quarantining all possibly-contributing herds when a milk silo tests positive could make it more effective, the team said. "Considering the currently widespread nature of H5N1 in the United States, frequent on-site testing, including of individual herds, may be necessary for timely and maximally effective control measures for bovine H5N1 outbreaks," they wrote.

USDA confirms detections in live markets in 2 states

In other H5N1 developments, APHIS today reported confirmations in poultry from live-bird markets in Pennsylvania and New Jersey. The detection from Pennsylvania is from Philadelphia County and the one from New Jersey is from Union County.