By Margaret Battistelli Gardner
Bird flu—specifically H5N1—is no longer just a poultry problem in Asia. What started as a major United States outbreak, first in wildlife, then in poultry, and later in dairy cattle, is raising new concerns about food security, the economy, the health of farm workers, and the potential for future human outbreaks.
In a commentary published in The Journal of Infectious Diseases, Dr. Gregory Gray, a professor in the Division of Infectious Disease and Department of Microbiology and Immunology at The University of Texas Medical Branch (UTMB), writes that vaccinating dairy cattle could be one of the most important steps the U.S. takes to get ahead of this evolving threat.
"This virus has changed and now seems to have become entrenched or 'enzootic' in North American wildlife," Gray said. "We used to think of H5N1 as a bird problem in Asia. Now it's clearly something bigger and here in our own backyard, and we need to respond accordingly. At first, people thought this was a one-off event, but it spread—and it's still spreading."
The current wave of H5N1 began sweeping through U.S. poultry flocks in 2022, leading to the loss of more than 190 million birds. By 2024, the virus had made an unexpected jump into dairy cattle. So far, more than 1,000 dairy herds across at least 19 states have been affected, contributing to an estimated $14 billion hit to the U.S. economy, including roughly $4 billion in losses to the dairy sector alone.
Viruses like H5N1 evolve over time. The more they spread and the more species they infect, the more opportunities they have to change. Dairy cattle may now be acting as what researchers describe as a kind of "training ground" for the virus to adapt to mammals, including humans.
"Every H5N1 infection in animals or humans is like a roll of the dice," Gray said. "Most of the time, nothing major happens. But the more chances the virus gets, the greater the risk that the virus will become more dangerous to animals or humans."
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