The United States has entered a "forever war" with bird flu, as the H5N1 pandemic threat continues to loom large, with experts warning of a potentially devastating outbreak. According to Martha Nelson, a computational biologist and staff scientist at the National Institutes of Health, the virus is "evolving in ways we haven't seen before" and is "adapting to mammals, and it continues to show new tricks."

The Centers for Disease Control and Prevention (CDC) and other experts have described the threat posed by the virus as low, but Nelson warns that the likelihood of an H5N1 human pandemic "is growing." While the vast majority of the 70 confirmed human cases in the US have been mild, there have been at least four hospitalizations and one death in North America since November. The virus has also spread widely in domestic and wild animals, with exact transmission routes remaining unclear.

The outbreak has been ongoing for over two years, with almost 1,000 dairy herds infected since the virus was first detected in cows in March 2024. Initially, scientists thought the outbreak would burn itself out, but the latest events have proven that unlikely. The virus has mutated into a potentially more dangerous version, known as the D1.1 genotype, which is now circulating among wild birds and poultry and has spilled over into dairy cows at least twice in 2025.

Experts warn that the virus could potentially spread from mammal to mammal, with rodents being a particular concern given their ability to infest human dwellings and act as vectors of disease. While there have been no confirmed instances of human-to-human transmission, the risk remains, and experts are urging for increased mitigation and monitoring efforts.

Backyard poultry and pets, especially cats, are also vulnerable to the virus and could potentially transmit it to humans. Health officials have confirmed dozens of infections in domestic cats, and pet owners are being advised to take precautions to prevent transmission.

Farms are seen as a key locus of prevention, with experts calling for increased surveillance and biosecurity efforts to reduce the risk of transmission. However, the task is daunting, and major challenges remain, including the need for sustained investment in vaccination efforts and the lack of communication from federal agencies.

The USDA has begun requiring states to submit samples of raw milk for H5N1 testing, but experts say this is not enough, and individual cows on affected farms need to be tested to reduce overall human exposure to the virus. Biosecurity efforts on farms also need to be ramped up and sustained, with measures such as sanitizing vehicles and equipment, preventing contact between wildlife and farmed animals, and restricting animal transport.

Despite the challenges, experts are urging for a sustained response to the outbreak, warning that the consequences of inaction could be devastating. As Nelson puts it, "We are flirting with a massive global pandemic that could be equal to or greater than COVID-19," and it's essential that we harness the knowledge and tools built during the pandemic to respond to this new threat.