By Jamie Martin
The US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed a new spillover of H5N1 avian flu in dairy cattle. This new detection involves the D1.1 genotype, which has been circulating in wild birds and linked to human infections.
Previously, all H5N1 cases in dairy herds were linked to the B3.13 genotype, believed to have originated from a single spillover event in late 2023 or early 2024.
While the B3.13 strain has caused mild conjunctivitis in dairy workers and poultry cullers, the D1.1 genotype has been associated with more severe cases.
The new strain was identified through milk testing in Nevada, following the recent detection of H5N1 in multiple dairy herds across the state. Nevada officials have taken action to control the spread by managing large populations of European starlings, a non-native species that can transmit the virus to livestock.
Despite the new spillover, APHIS emphasized that the discovery does not change its eradication strategy. The agency continues to implement its National Milk Testing Strategy, which has expanded to 36 states and now monitors milk from two-thirds of the nation’s dairy herds.
University of Minnesota epidemiologist Michael Osterholm, PhD, MPH, commented on the situation, stating, "We shouldn't be surprised about a new spillover to cattle, given the very significant activity in waterfowl across much of the United States."
USDA is working with Nevada officials to investigate the situation and limit further spread. The agency plans to release a technical brief and post sequencing data on GenBank in the coming week.
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Categories: National