by A. J. Campbell, Meredith Shephard, Abigail P. Paulos, Matthew D. Pauly, Michelle N. Vu, Chloe Stenkamp-Strahm, Kaitlyn Bushfield, Betsy Hunter-Binns, Orlando Sablon, Emily E. Bendall, William J. Fitzimmons, Kayla Brizuela, Grace E. Quirk, Nirmal Kumar, Brian McCluskey, Nishit Shetty, Linsey C. Marr, Jenna J. Guthmiller, Jefferson J. S. Santos, Scott E. Hensley, Edith S. Marshall, Kevin Abernathy, Adam S. Lauring, Blaine T. Melody, Marlene K. Wolfe, Jason Lombard, Seema S. Lakdawala Transmission routes of highly pathogenic H5N1 between cows or to humans remain unclear due to limited data from affected dairy farms. We performed air, farm wastewater, and milk sampling on 14 H5N1-positive dairy farms across two different California regions. Infectious virus was detected in the air in milking parlors and in wastewater streams, while viral RNA was found in exhaled breath of cows. Sequence analysis of infectious H5N1 virus from air and wastewater samples on one farm revealed viral variants