TEXAS PANHANDLE — Researchers from the University of Pittsburgh School of Public Health published a study in Science Advances on June 19, 2026, detailing how H5N1 bird flu infects dairy cattle. The study found that H5N1 primarily infects cattle through udder tissue, not the lungs, distinguishing it from how the virus affects other mammalian species.

H5N1 bird flu began infecting U.S. cattle in early 2024, with the disease first appearing in dairy cattle in the Texas Panhandle. In cows, H5N1 infection caused severe infection in the udders and largely spared the lungs, resulting in mammary gland tissues developing severe necrotizing mastitis, an inflammatory condition that causes damage.

The research team employed various scientific methods, including binding experiments, staining methods, and ultra-high-resolution imaging, to reach their conclusions. They determined that only N-linked sialic acid receptors could bind to H5N1. These N-linked sialic acid receptors were pervasively present in cow udders but were virtually absent in cow airway tissue. Initial studies by other groups had suggested that flu-related glycan receptors were present in the noses, tracheas, and lungs of cows.

Suresh Kuchipudi, chair of Infectious Diseases and Microbiology at Pitt Public Health, collaborated on the study with Lauren E. Pepi of Harvard Medical School. Kuchipudi stated, "We hadn't even remotely considered that cattle could be a host for H5N1." He added, "If a cow is infected, it sheds a lot of virus into the milk."

The virus spread from herd to herd and contaminated environments before it was identified. There have been instances of cats dying after being fed raw milk, while pasteurization is effective at killing the H5N1 virus. H5N1 affects more than 100 bird and mammal species globally.

Kuchipudi also noted the implications of this research for future disease monitoring. "We can preemptively screen different species and different tissues within them for susceptibility," he said. Other authors from the University of Pittsburgh on the study included Surabhi Srinivas, Shubhada K. Chothe, Santhamani Ramasamy, Sougat Misra, Noel Chandan Nallipogu, and Lindsey LaBella. Yin-Ting Yeh from Pennsylvania State University, May Wang from Harvard University, and Heidi L. Pecoraro and Brett T. Webb from North Dakota State University were also authors. The research received support from Pitt Public Health and the U.S. Department of Agriculture's National Institute of Food and Agriculture.