Testing for HPAI H5N1 is crucial to achieve disease freedom from this virus in U.S. dairy cattle. USDA works closely with Federal, State, and industry partners to ensure our testing activities are comprehensive.
APHIS provides all H5 livestock testing through the National Animal Health Laboratory Network (NAHLN) and National Veterinary Services Laboratories (NVSL), free of charge. We receive samples via many efforts and programs:
- Milk testing per the December 2024 Federal Order and National Milk Testing Strategy
- Interstate movement testing under the April 2024 Federal Order
- Voluntary Dairy Herd Status Program
- Testing programs some States have designed per their unique authorities
- Testing before interstate movement to fairs, exhibitions, or sales as part of State programs
- For producers interested in learning the status of their livestock herds
As the situation changes, we will continue to keep pace with the latest science on HPAI and post updated information below.
Weekly Updates
Testing information is updated weekly on Fridays.
- Total PCR tests run at NAHLN and NVSL in year 1 (April 2024-April 2025): 210,146
- Total PCR tests run at NAHLN and NVSL in year 2 (May 2025-present): 47,658
Testing at NAHLN and 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.
Through all testing efforts and programs, we have received samples from each of the 48 contiguous States. We report any confirmed positive findings through our online dashboard. We also upload whole genome sequences of each detected virus to public databases.
APHIS Testing Activities and Programs
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 and accompanying guidance 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, facilitates comprehensive H5N1 surveillance of the Nation’s milk supply and dairy herds.
In April 2024, USDA announced a Federal Order that requires testing of lactating dairy cows before interstate shipment and mandatory reporting of positive test results connected with those tests. These requirements remain in effect. USDA's additional Federal Order announced in December 2024 complements and enhances this existing order.
Learn More About USDA's April 2024 Federal Order and Requirements
The Dairy Herd Status Program is a voluntary program that offers dairy producers the option to monitor their herds via weekly bulk milk samples before moving them across State lines, without having to test each individual animal.
Learn More About the Dairy Herd Status Program and How To Participate
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.