You’ve probably heard of bird flu, a severe respiratory disease that’s highly infectious in birds. The pathogen responsible — a virus known as H5N1 — has caused thousands of deaths globally in other animals too, including already threatened or endangered marine mammals.
Polar bears have been dying from bird flu, likely after eating infected bird carcasses. Adding insult to injury, pollution interferes with the bears’ immune system, making them less able to fight off infections.
In late 2023, over 17,000 southern elephant seal pups died from bird flu in Argentina. The pups were still nursing, so the only way to account for the mass die-off is seal-to-seal transmission of the virus — an ominous development in the virus’ spread.