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Historically these hitchhikers were predominantly low pathogenic avian influenza viruses, meaning they did not cause high mortality in wild birds. Then about two years ago, a highly pathogenic lineage of avian influenza took advantage of the flyways and became an unprecedented global pandemic. Likely millions of wild birds have been killed worldwide and the breadth of species impacts have been astounding:

• 250,000 birds have died in Peru, including Peruvian pelican (Pelecanus thagus), guanay cormoran (Phalacrocorax bougainvillii), and sanderlines (Calidirs alba).
• 13,200 Barnacle geese (Branta leucopsis) that breed in Svalbard have died, representing 30 percent of the population in that flyway.
• 8,000 migratory common cranes (Grus grus) died in Israel's Hula Valley during their migration to Africa between December 2021 and January 2022.

As the virus traversed continents, it crossed species barriers: 

• Outbreaks were reported in blue fox fur farms in Finland and in a mink farm in Spain.
• 8,000 South American sea lions (Otaria flavescens) have died along the Peruvian coastline.
• Grizzly bears, foxes, coyotes, skunks, raccoons, and other animals that feed on dead birds have been infected and died with severe disease, often showing neurological signs.
• 2,500 Caspian seals (Pusa caspica) were reported dead in a mass mortality event in Russia in early 2023.

Specialist of the Peruvian National Service of Protected Areas (SERNANP) collecting samples from a south American sea lion (Otaria flavescens). ©P. Colchao, WCS thanks to SERNANP.

For good reasons, scientists are advocating a watchful approach. Since 1900, avian influenza has caused five human pandemics, nearly all tracing back to an animal source—with the largest in 1918 killing an estimated 50 million people. In the last two decades, there have been hundreds of isolated human fatalities of people exposed to sick animals.

So far these spillover events have been self-limiting, and virologists point out that the ability to transmit among mammals is concerning but not yet reason to panic. The contemporary lineage that is wreaking havoc spent 25 years evolving in poultry, resulting in the deaths of at least 400 million domestic animals and US$20 billion of economic losses. In recent years it was likely responsible for egg and turkey shortages and rationing in your local grocery store. 

Beyond watchful waiting, efforts like Preventing ZOonotic Disease Emergence (PREZODE) are advocating salient steps to address the emergence of viruses at the source. The current avian influenza pandemic demands a reevaluation of our food systems and practices. Wild birds and mammals are the most current victims of our unsafe and unsustainable agricultural practices. If business as usual continues, there is a risk we could be next and victims of our own industrial food animal production.

It is clear that human intensification of poultry farming contributed to the emergence and spread of the virus. Prevention initiatives like PREZODE are needed to bring public, conservation, and livestock sectors together so that better policies are informed by health risks and costs alongside the economic drivers and constraints of the industry. We need to consider a reorientation of our approach to food production and promote sustainable practices that prioritize the health of ecosystems, all animals, and the well-being of humans.

The challenge at hand is not one that any nation or community can face alone. World Migratory Bird Day is a yearly reminder of the need for both international collaboration and action. Yes, it is imperative that we all work to increase surveillance of avian influenza virus in animals to track the continuing evolution and impacts of the pathogen. Moreover, the mass mortalities and frequency of outbreaks of migratory birds and other animals from this virus are sending us an urgent message.

We need more than watchful waiting. Efforts like PREZODE that get to the source and help foster better poultry industry practices and policies will help our oceans, lakes and wetlands continue to provide a safe stopover point for birds on their long journeys. The deaths of these incredible migratory birds are a direct result of our actions, and it is time to change course. Governments, NGOs, scientists, and communities must come together to implement prevention strategies, reevaluate food systems, and safeguard the health of our shared environment for generations to come. 

Dr. Sarah Olson is Director of Health Research at WCS (Wildlife Conservation Society) and a Member of PREZODE Steering Committee.

Carcass of a Sanderling (Calidris alba) positive to HPAI. Before dying, this migratory shorebird was found signs of disorientation, ataxia and nystagmus. ©P. Colchao, WCS. 

Specialist of the Peruvian National Service of Agricultural Health (SENASA) inspecting the mass mortality of Peruvian pelicans (Pelecanus thagus) in a breeding colony in the beginning of the outbreak in Peru. ©P. Colchao, WCS thanks to SERNANP.

Carcass of a common dolphin (Delphinus delphis) positive to HPAI found in the north of Peru. ©P. Colchao, WCS.