TL;DR: A highly pathogenic avian influenza (HPAI) strain, H5N1, is causing significant mortality among elephant seal pups in Patagonia, Argentina, with an estimated 17,000 deaths in 2023. This event is notable for its scale and suggests mammal-to-mammal transmission, raising concerns about the virus’s potential to spread among other mammals, including humans.

Massive Elephant Seal Mortality: Nearly 96% of elephant seal pups at three breeding sites in Patagonia died due to H5N1, contrasting sharply with the previous year’s successful weaning of 18,000 pups.

Mammal-to-Mammal Transmission: The seals likely had little interaction with infected birds, indicating a possible mammal-to-mammal transmission route.

Global Impact of H5N1: The virus has affected over 150 bird species worldwide, causing significant deaths in bird populations in South America, Greece, and the Netherlands.

Spread Among Mammals: H5N1 has been detected in various mammals, including pumas, foxes, skunks, brown bears, and endangered Caspian seals, with a polar bear death reported in Alaska.

Human Health Concerns: The World Health Organization urges preparedness for potential human spillover. Human infections are rare but could become more common if the virus evolves to transmit more easily between mammals.

Call for Collaborative Approach: There’s a need for a global, collaborative effort to monitor bird flu strains and develop vaccines to prevent another pandemic.