It has ravaged farms, decimated wild birds and spilled onto mammals. Could avian flu spark the next human pandemic? The Down to Earth team takes a closer look.
Ducks ‘most vulnerable species’ in France
Jean-Christophe Dardenne is a duck farmer in France's southwestern Gers region. Normally, his flocks would be used to roaming freely in the fields, but not anymore. A bird flu epidemic that has gripped Europe for over a year has forced authorities to impose a lockdown on farms across the country. It's been tough to handle, says Jean-Christophe, who doesn't have the necessary equipment to keep his animals indoors.
"Some flocks will never get to see the sun and daylight," he complains, adding that animals kept indoors will grow less quickly, leading to a loss in meat and foie gras production.
Jean-Christophe is among a lucky few to have been spared so far by the disease. But he lives in constant fear that one day the flu will be detected on his farm, and his ducks culled by local authorities.
"To me this type of management is absurd," he says. "It worries me a lot for the future."
Europe's worst outbreak
The highly infectious strain of bird flu has been ripping through farms for a number of years. Influenza A, also known as H5N1, was first detected at a goose farm in China in 1996. It can spread through entire flocks of birds through the animals' droppings and saliva.
This is the fourth wave of avian influenza to grip Europe since 2015, but also its worst outbreak on record, with nearly 50 million poultry culled in 2022. France ranks among the countries hit hardest by the disease, with nearly 16 million poultry killed to prevent the spread of the virus.
The way the disease is expanding has also set off alarm bells. It usually flares up in autumn before fading away in spring and summer. This outbreak, though, has defied all seasons.
But what really has scientists concerned is the flu's pandemic potential, as infections have been reported across a large spectrum of birds and other species, including mammals.
A Covid-19 scenario?
There's one question on everyone's minds: what about human transmission? H5N1 is currently considered a low risk to humans. But health authorities are on high alert. The more it continues to spread, the greater the chances are that it may evolve.
At France's National reference lab for avian influenza, every mutation is being watched closely to avoid this scenario. Samples from farms and wildlife collected across the country end up here for analysis.
Beatrice Grasland, a virologist, confirms the virulence of this outbreak. In 2022, they recorded 1,400 outbreaks in farms.
"It's unprecedented, nearly three times the numbers we had in previous outbreaks," she says.
For now, it's an avian virus, but the team of scientists is monitoring its possible transmission to other species, mammals in particular. A domestic cat recently became infected: a potential warning sign, according to Grasland.
"A single replication of the virus in this cat created mutations that enable the transmission of the virus among mammals," she warns.
Unlike the Covid-19 pandemic, the influenza vaccine already exists. But a bird flu pandemic could still wreak havoc.
"We're potentially dealing with a virus we humans have never encountered before. We would be facing an epidemic like we've never seen before and we would need to act very fast," Grasland explains.
Wild birds, hosts and latest victims of the virus
Scientists have been taken aback by the magnitude of this outbreak, mostly because wild bird mortalities have reached unprecedented levels.
Wild birds are usually the hosts and transmitters of the disease, but they are able to withstand the virus. Now, they've become the latest victims.
"In France, two major groups of wild birds have been affected: birds of prey, which is unheard of. Then, we have seabirds," explains Cedric Marteau from the French League for the Protection of Birds (LPO).
The rate of infection among France's sole gannet colony in Brittany has been spectacularly high. More than 40 percent of adults have died and 90 percent of chicks.
"It will be very difficult for bird populations to recover," warns Marteau. His main concern now is that species threatened with extinction could suffer a similar fate.
In the outskirts of Paris, the death toll among wild birds has also risen sharply. Some 1,400 dead birds were collected in under three weeks in February: mainly seagulls, but also ducks, a swan and moorhen.
"I’ve never seen anything like it," says Sébastien Viprey, Biodiversity officer for the Paris-Grand Orly region.
Vaccine rollout by 2023
For veterinary officials, it's become increasingly clear that the epidemic won't be tamed without resorting to vaccines.
Vaccines are set to be rolled out in French farms starting in September 2023, according to a deadline set by the government. Jean-Luc Guérin, from the French National Veterinary School in Toulouse, is in charge of carrying out trials before the vaccination campaign officially begins.
His team has partnered with farms in order to test two different vaccines in real-life conditions. They monitor the animals to detect antibodies as well as conducting molecular tests to make sure the virus does not continue to circulate silently among flocks.
"In France, we know that ducks play a major role in what we call the 'dynamics of infection'. That means that if we are able to contain infections in ducks, then we'd be making great strides in the fight against the disease," says Guérin.
One of the main challenges with the avian influenza vaccine is being able to certify that the animals that get jabbed aren't healthy carriers of the disease, he explains. That has long fuelled scepticism in the international community, but for Guérin we have gone past the point of debate.
"We can see quite clearly that the nature of the risk has changed and we no longer have a choice," he concludes.