The H5N1 Avian influenza is decimating bird populations around the world. More than 136 million birds have been affected in the US since the disease arrived in 2022. More than 5 million egg-laying chickens died in the first 16 days of 2025.

H5N1 vaccines have been previously licensed, and millions are in the national stockpile. But even with the news of the country’s first human death due to bird flu, vaccination isn’t yet recommended.

The United States has reported its first outbreak of H5N9 bird flu in poultry on a duck farm in California, the World Organisation for Animal Health (WOAH) said on Monday.

A new strain of bird flu has been detected in California, which could make the ongoing outbreak more challenging to handle.