When bird flu [H5N1] first struck dairy cattle a year ago, it seemed possible that it might affect a few isolated herds and disappear as quickly as it had appeared.

Instead, the virus has infected more than 900 herds and dozens of people, killing one, and the outbreak shows no signs of abating.

...

For at least a year, H5N1 has been infecting dairy cattle, which were not known to be susceptible to this type of influenza. [...]

And in 2024, the virus infected 67 Americans, compared with just one in the years before, in 2022. The sources of these infections are not all known; one person may have transmitted the virus to someone in their household.

Many of these developments are classic steps toward a pandemic, said Dr. James Lawler, a director at the University of Nebraska's Global Center for Health Security. But, he noted, "where those were really supposed to trigger accelerated and amplified actions at the federal, state and local level, we've just kind of shrugged when each milestone has passed."