In late March 2024, scientists were taken by surprise when the bird flu virus, H5N1, was detected in cows a development that shifted long-standing concerns about the virus’s jump from birds to pigs. Even more surprising was the discovery of the virus in cows’ mammary glands, as it had previously been considered a respiratory pathogen.
By April and May, human cases began appearing, first in Texas and Michigan, and later in Colorado, suggesting the virus was spreading more widely among livestock than initially understood. Alarm grew when extremely high levels of virus particles between 10,000 and 10 million per milliliter were found in milk samples, prompting urgent meetings between scientists and government agencies.
Despite these developments, the response was slow and underwhelming, hindered further by government cutbacks in public health funding. Over a year later, experts are grappling with two major questions: could H5N1 become a pandemic, and how can such an event be prevented?
As of early May 2025, the CDC still considers the risk to the public low. No known person-to-person transmission has occurred. Of the 70 confirmed U.S. cases, most were traced to exposure on dairy farms. Still, the virus’s ability to mutate means continued monitoring is essential.
For a virus to spread efficiently between people, it must bind to human cell receptors in the nose, throat, or lungs. So far, H5N1 does not appear to have developed this capacity. However, experts caution that viruses can evolve quickly, and just a few mutations could potentially allow efficient human-to-human transmission. At that point, household transmission would likely precede wider community spread.
The possibility of a rapid shift to pandemic status is not theoretical. COVID-19 demonstrated how quickly a virus can spread once human-to-human transmission is established. Within two months of initial detection, COVID-19 had become a global pandemic. A similar scenario with H5N1 is possible, although the exact path to such a transition remains uncertain.
There are ongoing efforts to monitor the situation. Dairy herds are tested before interstate transport, and bulk milk samples are analyzed in many states. Most of the milk supply is tested regularly under national programs. However, testing among farm workers is lagging, and experts have identified potential signs of exposure in some workers, with about 7% showing antibodies to the virus in one study.
Public awareness remains low. A survey of 10,000 people in 2024 found that fewer than 20% were aware the virus had infected cows. Less than 30% said they would change their behavior or diet in response, and many expressed unwillingness to get vaccinated if a shot became available.
Experts urge the public to take basic precautions. Avoid raw milk and cheeses, which can carry the virus. Keep pets, especially cats, indoors to avoid exposure to infected birds. Take care when handling bird feeders or coming into contact with wild birds. And during flu season, get the flu shot to reduce the risk of dual infections.
Crucially, people are encouraged to reach out to their state departments of agriculture, urging more oversight and control of H5N1 in livestock. Strengthening local monitoring and response capabilities may be key to preventing the next pandemic.
