Macaques exposed to doses of the 2.3.4.4b clade of H5N1 via the nose and windpipe had more severe disease.
The latest confirmation likely reflects follow-up testing of a San Francisco child whose exposure to the virus is still under investigation.
As sporadic H9N2 infections continue in China, rarer H10N3 infections in the past few years now total 4.
Tests results are pending for additional commercial raw pet food samples.
Officials are still investigating how the child contracted the virus. In other developments, the USDA today confirmed the first outbreak in Puerto Rico's poultry.
Also, Maryland reported a preliminary positive in a broiler flock, its first at a commercial farm since 2023.
This is the 19th human H5N1 case identified in Cambodia since early 2023.
In other developments, the USDA confirmed a few more H5N1 avian flu detections in dairy cattle and poultry.
H5N5 viruses continue to expand their geographic and species range, with spillovers to domestic birds reported in a few European countries.
Testing has now scaled up to 28 states, covering at least 65% of the nation's production.
