Study: https://www.nature.com/articles/s41586-024-07766-6
Quotes from the news article:
The bird flu strain found in cows in the United States is not easily transmitted through the air among ferrets, a new study shows, although the scientist who led the work said it had shown some ability to spread this way.
Ferrets are considered to be the best small mammal for studying influenza virus infection and transmission and are often used to inform assessments of the public health risk of emerging viruses.
In the experiment led by researchers at the University of Wisconsin-Madison, ferrets infected with a sample of the H5N1 bird flu strain were placed near healthy animals, but not close enough for physical contact.
None of the four healthy ferrets exposed in this way became ill, and no virus was recovered from them during the study.
However, one of the ferrets had produced antibodies to the virus, the researchers later found, suggesting it had been infected.
TLDR:
"It is good news that the virus does not have extensive transmissibility between ferrets through the air, but it is concerning that it has the ability to transmit [at all in this way]," said study author and flu virologist Yoshihiro Kawaoka.
No evidence yet of human-to-human transmission
A virus that can spread easily through the air between humans would pose a greater pandemic threat than H5N1 currently does.