In 2024, at least 66 human cases of bird flu have been reported in the United States, each one raising the risk of another pandemic like COVID-19. So far, most cases have been described as “mild,” which means they weren't hospitalized.

It’s an ecological wonder not seen anywhere else in the world, and a bonanza for scientists who are looking to stop the next pandemic. This year, their work has taken on new urgency as a dangerous flu virus,