Though H5N1 has been circulating nationwide in wild birds, domestic poultry, and mammals since 2022, you may have only been hearing about it recently because of its jump to dairy cattle. The first positive case was documented in Texas on March 25, 2024.

Gov. Newsom declared a state of emergency as the virus continues to infect dairy herds across the country — including more than 600 in California.

When, where and how the H5N1 bird flu virus may evolve and its capacity to spark a pandemic is hard to predict — in part, some researchers say, because of federal restrictions on gain-of-function research.