Bird flu strain raises alarm as virus kills South American wildlife

SAO PAULO — The deadly H5N1 bird flu virus has spread more aggressively than ever before in wild birds and marine mammals since arriving in South America in 2022, raising the risk of it evolving into a bigger threat to humans, according to interviews with eight scientists.

Of more immediate concern is evidence the disease, once largely confined to bird species, appears to be spreading between mammals. This strain has already killed a handful of dolphins in Chile and Peru, some 50,000 seals and sea lions along the coasts, and at least half a million birds regionwide.

To confirm mammal-tomammal transmission, scientists would likely need to test infections in live animals.

“It’s almost certainly happened,” said Richard Webby, a virologist at St. Jude’s Children’s Research Hospital in Memphis, Tennessee. “It’s pretty hard to explain some of these large infections and die off without having mammalto-mammal spread.”

The strain has shown up in dozens of bird species, including some migrating species, which can spread it beyond the region, scientists told Reuters.

As climate change escalates, animals will be forced to move into new territories, mixing with one another in new ways and possibly boosting opportunities for the virus to further mutate.

“It’s a matter of time before you will detect the first South American strain in North America,” said Alonzo Alfaronunez, a viral ecologist at University of Copenhagen.

HUMAN RISK

The growing concern has prompted the 35 countries in the Pan American Health Organization (PAHO) to convene regional health experts and officials at a meeting this week in Rio de Janeiro.

The group plans to launch the world’s first regional commission to oversee bird flu monitoring and response efforts, a PAHO official told Reuters. This has not been previously reported.

Since the virus was first detected in Colombia in October 2022, there have been two known cases in humans on the continent, one each in Ecuador and Chile. Both came from exposure to infected birds.

While those patients survived, H5N1 bird flu is deadly to humans in roughly 60 per cent of cases worldwide.

The World Health Organization is unlikely to raise the risk level for humans from the current “low” without evidence of human-to-human transmission or mutations adapted to human receptors, experts said.

Drugmakers, including GSK and Moderna, have said they are developing bird flu vaccines for humans, and have the capacity to produce hundreds of million so doses within months utilizing production lines used for seasonal flu vaccines.

“We’re seeing (the virus) doing little evolutionary steps that are on the long-term moving towards a potential human infection,” said Ralph Vanstreels, a University of California, Davis researcher studying South American variants of H5N1.