The U.S. Department of Agriculture (USDA), Food and Drug Administration, Centers for Disease Control and Prevention, and State veterinary and public health officials are responding to cases of highly pathogenic avian influenza (HPAI) in livestock.
APHIS is providing confirmatory testing for samples from livestock and keeping pace with the latest science on HPAI. As the situation changes, we will continue to post updated information below.
National Milk Testing Strategy
On December 6, 2024, USDA announced the start of our National Milk Testing Strategy (NMTS), which builds on measures we have taken since the start of the HPAI H5N1 outbreak in dairy cattle. To mark the official beginning of the strategy, USDA issued a new Federal Order (119.6 KB), as well as accompanying guidance (363.27 KB), requiring that raw (unpasteurized) milk samples nationwide be collected and shared with USDA for testing. This new guidance, which was developed with significant input from State, veterinary, and public health stakeholders, will facilitate comprehensive H5N1 surveillance of the Nation’s milk supply and dairy herds.
The NMTS is designed to increase our understanding of the virus’ spread in the United States; support the rapid implementation of enhanced biosecurity measures to decrease the risk of transmission to other livestock; and inform critical efforts to protect farmworkers to help lower their risk of exposure. This strategy is an important additional step to proactively support effective biosecurity measures, which is key for States and farmers to contain and eliminate H5N1 infections from their livestock and to eliminate HPAI in livestock across the U.S. dairy population.
Roadmap: National Milk Testing Strategy (95.32 KB)
Weekly Updates
Testing at the National Animal Health Laboratory Network (NAHLN) and National Veterinary Services Laboratories (NVSL) is complex; the number of tests conducted is not equivalent to animals tested. The testing figure may include multiple samples collected from a single animal, samples tested independently or pooled, samples tested more than once, and testing for purposes such as on-farm research studies to continue to learn more about this virus in livestock. As such, the number of affected herds provides a much more accurate picture of the evolving situation than the number of tests conducted.
Testing information is updated weekly on Fridays by 9 a.m. ET.
- Total PCR tests run at NAHLN and NVSL (since April 2024): >89,319
- Pre-movement tests conducted under the Federal Order: 22,663
Genetic Sequencing
USDA makes genetic sequences from the U.S. H5N1 clade 2.3.4.4b influenza virus, including those from samples associated with the dairy cattle event, available on GISAID (the Global Initiative on Sharing Avian Influenza Data) and the National Center for Biotechnology Information (NCBI) Sequence Read Archive (use search term “WGS of H5N1”).
We post this information—first in raw format and then curated as the sequences are interpreted and quality checked in light of epidemiological information—in the interest of public transparency and ensuring the scientific community has access to this information as quickly as possible to encourage disease research and development.