Elephant seals lie dead on a beach in Argentina following an outbreak of avian influenza in the region in 2023. Credit: Maxi Jonas
Key points:
- H5N1 has adapted to spread between birds and marine mammals, posing an immediate threat to wildlife conservation.
- Since 2022, H5N1 in South America has killed at least 600,000 wild birds and 50,000 mammals.
- The virus is now heading southward from South America, and scientists are concerned about its potential impact on penguins and other wildlife in Antarctica.
The highly pathogenic avian influenza virus H5N1 has adapted to spread between birds and marine mammals, posing an immediate threat to wildlife conservation, according to researchers from the University of California, Davis.
For the study, scientists collected brain samples from four sea lions, one fur seal and a tern found dead at the most-affected sea lion rookery in Argentina. All tested positive for H5N1.
Genome sequencing revealed that the virus was nearly identical in each of the samples. The samples shared the same mammal adaptation mutations that were previously detected in a few sea lions in Peru and Chile, and in a human case in Chile. Of note, the scientists found all these mutations also in the tern, the first such finding.
“This confirms that while the virus may have adapted to marine mammals, it still has the ability to infect birds,” said first author Agustina Rimondi, a virologist from the National Institute of Agricultural Technology (INTA) in Argentina. “It is a multi-species outbreak.”
We know this because the virus sequence in the tern retained all mammal-adaptation mutations. Such mutations suggest a potential for transmission between marine mammals.
“This virus is still relatively low risk for humans,” said senior author Marcela Uhart, a wildlife veterinarian with the UC Davis School of Veterinary Medicine’s One Health Institute. “As long as the virus continues to replicate in mammals, it may make it a higher concern for humans. That’s why it’s so important to conduct surveillance and provide early warning.”
In 2020, avian influenza began killing tens of thousands of sea birds in Europe before moving to South Africa. In 2022, it entered the U.S. and Canada, threatening poultry and wild birds. It migrated to Peru and Chile in late 2022. Then, in February 2023, highly pathogenic avian influenza entered Argentina for the first time. In August 2023, the virus was found in sea lions at the tip of South America on the Atlantic coastline of Tierra del Fuego for the first time. From there, it moved swiftly northward with deadly results, first for marine mammals and later for seabirds.
Since 2022, H5N1 in South America has killed at least 600,000 wild birds and 50,000 mammals, including elephant seals and sea lions in Argentina, Chile and Peru, and thousands of albatrosses in the Malvinas/Falkland Islands. Recent studies also show a large outbreak killed 70% of elephant seal pups born in the 2023 breeding season. Mortality rates reached at least 96% by early November 2023 in the surveyed areas of Península Valdés in Argentina.
The virus is now heading southward from South America, and scientists are concerned about its potential impact on penguins and other wildlife in Antarctica.