The expert who predicted Covid-19 already knows what the next pandemic will be

A virus already present in animals

The H5N1 virus is no longer just a theoretical threat. In April 2025, it was detected in a sheep on a Yorkshire farm—a first in the UK. Meanwhile, the United States is facing a surge of infections in dairy herds: more than 1,000 farms affected,  more than 168 million birds culled , and more than 70 confirmed human cases, including one death.

This isn’t the story of a thriller series: it’s reality.  The virus is actively circulating among birds, but also among mammals, which significantly increases the risk of transmission to humans.

The mechanics of pandemics: one mutation is enough

Quammen explains a simple but disturbing biological phenomenon: each infected bird harbors billions of replicas of the virus. Each replication is an opportunity for the virus to mutate. And one day, it could become capable of being easily transmitted between humans.

This is how Covid-19 went from an animal virus to a global scourge.  Bird flu could follow the same path.