While a bird flu pandemic remains unlikely, the growing outbreak of H5N1 in mammals, including dairy cattle and humans, is raising alarm among health experts, the New York Times reports.
The virus, which first emerged in 2022, has infected millions of birds and has now spread to other animal species, including cats, raccoons, and sea lions. Infections in cattle, which were previously thought to be immune to the virus, have become increasingly common, further complicating efforts to control its spread. Experts are monitoring the situation closely, as there are growing concerns that the virus could evolve to spread more easily among humans, triggering a more severe public health threat.
Since 2022, H5N1 has affected more than 136 million birds across the US, contributing to disruptions in agriculture and soaring egg prices. The virus has also been linked to a growing number of infections in mammals, with dairy cattle experiencing lasting health effects, including reduced milk production and spontaneous abortions. The spread of the virus to domesticated animals, such as cats, has raised further concerns, particularly after reports of contaminated raw pet food in the US.
While the virus is still considered a low risk to humans, with only a small number of infections reported so far, some experts worry that its continued spread and potential mutations could increase the risk of human-to-human transmission.
“This is a dangerous virus,” said Dr. Nirav Shah, principal deputy director of the Centers for Disease Control and Prevention (CDC).
Although the general public’s risk remains low, experts have acknowledged that the situation could change rapidly, and the virus may evolve in ways that make it more capable of infecting humans.
Health experts emphasize that H5N1’s potential to evolve into a more dangerous virus is cause for concern. The virus is currently circulating on farms without causing noticeable symptoms in some animals, making it harder to detect and contain. The virus’s ability to reinfect dairy herds after initial exposure and show milder symptoms raises the possibility that it could become endemic, with long-term risks of further mutations.
Despite these concerns, the response to the outbreak has been criticized for delays and inadequate measures. For example, the US Department of Agriculture (USDA) has faced criticism for its slow response to testing and its failure to implement thorough surveillance programs for dairy herds, particularly in Idaho. Meanwhile, farmworkers, who are at higher risk of exposure to infected animals, often lack the necessary protective gear and knowledge about how the virus spreads.
The lack of timely testing and data collection has hindered efforts to understand the virus’s evolution and assess its true impact. Experts like Dr. James Lawler from the University of Nebraska’s Global Center for Health Security argue that these missteps are reminiscent of the early days of the COVID-19 pandemic, when delayed responses led to missed opportunities for containment.
The virus’s capacity to infect humans has sparked increased attention, particularly after two severe cases in 2024—one involving a Louisiana resident who died from complications related to H5N1 and another involving a Canadian teenager who required life support due to organ failure. These cases are significant because, historically, most human infections have been linked to close contact with infected birds. However, the recent infections suggest the virus may be evolving to spread more efficiently in humans.
Experts are also concerned about the potential for the virus to mutate further, as a lab study in December demonstrated that a single mutation allowed the virus to infect human cells more easily. If such mutations continue, it could enhance the virus’s ability to spread among people, making the outbreak more difficult to contain.
While the federal government has taken steps to prepare for the possibility of a larger outbreak, experts believe that more needs to be done. The CDC recommends basic precautions, such as avoiding contact with sick or dead birds, avoiding raw milk or meat, and getting tested if flu-like symptoms develop. The federal government has also invested in surveillance and testing programs, but much of this funding has yet to yield results.
The US currently has a limited stockpile of vaccines for H5N1, although experts point out that these vaccines may need to be updated to match the evolving virus. The CDC also recommends the use of antiviral medications like Tamiflu, but studies have shown that the drug is not particularly effective in treating infections. Given the uncertainties surrounding the virus’s potential to evolve into a pandemic strain, some experts are concerned that the US may not be adequately prepared for a larger-scale outbreak.
While there is no immediate threat of a bird flu pandemic, health experts are cautious about the virus’s evolving threat. The spread of H5N1 to mammals and the increasing frequency of human infections highlight the need for ongoing surveillance and rapid response strategies. As Dr. Louise Moncla, an evolutionary biologist at the University of Pennsylvania, warned, the virus’s potential to evolve into a more dangerous form means that health authorities must remain vigilant.
