Avian flu is infecting more mammals. What does this mean for us?

In her three decades of working with elephant seals, Dr. Marcela Uhart had never seen anything like the scene on the beaches of Argentina's Valdés Peninsula , last October.

It was high breeding season; the beach should have been teeming with harems of fertile females and enormous males fighting for dominance. Instead, it was "just carcasses upon carcasses," recalls Dr. Uhart, who directs the Latin American Wildlife Health Program at the University of California, Davis.

H5N1, one of several viruses that cause avian flu, has already killed at least 24,000 South American sea lions along the continent's coasts in less than a year. Now it was the turn of the elephant seals.

Pups of all ages, from newborns to completely weaned, lay dead or dying on the line high tide. The sick puppies lay listless, foam oozing from their mouths and noses.

Dr. Uhart called it "a picture of hell."

In the weeks that followed, she and a colleague protected themselves from head to toe with gloves, gowns and masks, and watered themselves periodically. themselves with bleach - carefully documented the devastation. Team members stood atop nearby cliffs and assessed the toll with drones.

What they discovered was astonishing: the virus had killed around 17,400 seal pups, or more than 95% of the young animals in the colony.