A new strain of highly pathogenic avian influenza (HPAI) has been detected in dairy cattle in Nevada, according to the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS). The discovery marks a shift from previous bird flu outbreaks in cows, raising fresh concerns over its spread and impact.
New Bird Flu Strain Found in Six Dairy Herds
Officials confirmed that the newly identified strain, genotype D1.1, was discovered in six dairy herds. This differs from genotype B3.13, the bird flu variant that has been spreading in cows across the United States since last year.
The D1.1 strain has been predominantly found in wild birds and mammals over the past fall and winter and has now spilled into domestic poultry and cattle. The USDA identified the strain through genome sequencing of milk samples collected on January 31 as part of its nationwide milk-testing program.
Federal and State Agencies Investigating Spread
APHIS, in coordination with the Nevada Department of Agriculture, is conducting further investigations to understand how the virus is spreading and to limit its reach. Additional testing is underway on affected farms to track the virus’s movement and ensure containment.
The latest outbreak in Nevada has led to quarantines on two dairy cattle herds in Nye and Churchill counties. Officials are testing the Churchill County cases to confirm the specific strain, though early results suggest it matches a bird flu strain previously detected in wild birds across North America.
J.J. Goicoechea, director of the Nevada Department of Agriculture, emphasized the need for strict biosecurity measures to prevent further spread, urging farmers and ranchers to keep equipment clean and follow rigorous animal health safety protocols.
Human Cases Linked to the New Strain
The D1.1 strain has already been linked to severe human infections. In Louisiana, it was tied to the first U.S. human fatality connected to bird flu. The individual, over the age of 65, had underlying health conditions and was exposed to wild birds and a non-commercial backyard poultry flock.
In British Columbia, a teenager infected with the same strain was hospitalized in critical condition last fall. Outbreaks have also been reported in Washington state.
Bird Flu’s Growing Reach in the U.S.
Since March 2024, nearly 958 cow herds across 16 states have tested positive for H5N1 avian influenza, according to the USDA. The Centers for Disease Control and Prevention (CDC) reports 67 confirmed human cases of bird flu in the United States across eight states since April 2024.
Despite the discovery of the new strain, federal officials say the outbreak does not change their strategy for eradicating the virus. The USDA plans to publish a technical brief on the findings in the coming weeks and share genetic data on the virus for further scientific analysis.
Health experts continue to monitor the situation, stressing that early detection and containment efforts remain crucial in preventing wider spread among livestock and humans.
