The next pandemic? Avian flu, a silent pandemic that is decimating animals

I am referring to the highly pathogenic strain of avian influenza H5N1 (HPAI H5N1) which has killed millions of birds and an unknown number of mammals, especially in the last three years.

[Un article de The Conversation écrit par Diana Bell, Professeur de biologie de la conservation, Université d’East Anglia].

This strain appeared in domestic geese in China in 1997 and quickly spread to humans in Southeast Asia, with a mortality rate of 40 to 50%. My research group first came into contact with the virus in 2005 when it caused the death of Owston palm civets, an endangered mammal, that were part of a captive breeding program in Cuc Phuong National Park, Vietnam.

It is unknown how these animals contracted bird flu. Their diet consists mainly of earthworms, so they have not been infected by eating sick poultry, as has happened to captive tigers in the region.

This discovery prompted us to compile all confirmed cases of death from avian flu in order to assess the extent of the danger that this virus could represent for wildlife.

Here’s how a virus recently detected in Chinese poultry farms came to threaten a significant part of the world’s biodiversity.

The H5N1 virus appeared on a Chinese poultry farm in 1997. ChameleonsEye/Shutterstock

The first signs

Until December 2005, most confirmed infections had been found in a few zoos and shelters in Thailand and Cambodia. Our 2006 study showed that almost half (48%) of the different bird groups (or “orders,” depending on taxonomists) included a species that had reported deaths from avian flu. These 13 orders represent 84% of all bird species.

Twenty years ago, we estimated that circulating strains of H5N1 were likely highly pathogenic to all orders of birds. We also observed that the list of species confirmed to be infected included globally threatened species and that important habitats, such as the Mekong Delta in Vietnam, are near outbreak sites. in poultry.

Mammals known to have been exposed to avian flu in the early 2000s include primates, rodents, pigs and rabbits. Large carnivores such as Bengal tigers and clouded leopards have died, as have domestic cats.

Zoo animals that ate infected poultry were among the first victims of avian flu.

Our 2006 paper showed the ease with which this virus crosses the species barrier and suggested that it could one day pose a pandemic threat to global biodiversity.

Unfortunately, we were right.

Avian flu: a spreading disease

Nearly twenty years later, bird flu is killing species from the High Arctic to the Antarctic Peninsula.

In recent years, avian influenza has spread rapidly in Europe and infiltrated North and South America, causing the deaths of millions of poultry and various species of birds and mammals. According to a recent article, 26 countries have reported the deaths of mammals of at least 48 different species from the virus since 2020, when the number of infections last increased.

Sea lions killed by bird flu in Chile, April 2023. In recent years, the virus has spread rapidly in Europe and infiltrated North and South America. (Patricio Banda/EPA-EFE)

Even the ocean is not safe. Since 2020, 13 species of aquatic mammals have been affected, including sea lions, porpoises and dolphins, some of which are dying by the thousands in South America. It is now confirmed that a large number of land-dwelling scavenger and predator mammals, such as cougars, lynx, and brown, black and polar bears, are also affected.

The UK alone has lost more than 75% of its great skuas and experienced a 25% decline in its gannets. The recent decline of sandwich terns (35%) and common terns (42%) is also largely caused by the virus.

A small black and white bird in pain on the shore
A guillemot dying of bird flu in Berwickshire, England. June 2022. (Roy Waller/Alamy Stock Photo)

Scientists have not yet managed to completely sequence the virus in all affected species. Research and sustained monitoring could tell us how well it can adapt and whether it can spread to other species. We know it already infects humans – with a few genetic mutations it may become more contagious.

At the crossroads

From 1er January 2003 to December 21, 2023, there have been 882 cases of human infection with the H5N1 virus reported in 23 countries, of which 461 (52%) were fatal.

More than half of the deaths occurred in Vietnam, China, Cambodia and Laos. Infections transmitted from poultry to humans were first recorded in Cambodia in December 2003. Sporadic cases were reported until 2014, then there was a hiatus until 2023, when there were 41 deaths for 64 cases. The H5N1 subtype has been detected in poultry in Cambodia since 2014.

In the early 2000s, the circulating H5N1 virus had a high mortality rate in humans. It is therefore worrying that people are dying again after coming into contact with poultry.

A person wearing a mask and suit sprays surfaces in a coastal wetland
A quarantine official disinfects a wintering area for migratory birds in Jeju, South Korea. February 2024. (EPA-EFE/Yonhap)

The H5 subtypes of avian influenza are not the only ones of concern to humans. The H10N1 virus was originally isolated from wild birds in South Korea. Its presence has been reported in samples from China and Mongolia.

Recent research has shown that these virus subtypes are pathogenic in laboratory mice and ferrets and could infect humans. The first person confirmed to be infected with the H10N5 virus died in China on January 27, 2024, but they also had seasonal influenza (H3N2). She had been in contact with live poultry which tested positive for the H10N5 virus.

Endangered species have suffered deaths from bird flu over the past three years. It has just been confirmed that the virus has claimed its first victims on the Antarctic Peninsula among great skuas, posing an imminent threat to penguin colonies whose eggs and chicks are eaten by great skuas. The virus has already killed Humboldt penguins in Chile.

A colony of penguins
Penguin colonies are already threatened by climate change. (AndreAnita/Shutterstock)

How can we stem this tsunami of H5N1 and other avian flus? There is a need to completely overhaul poultry production globally and make farms self-sufficient in raising eggs and chicks instead of exporting them. Furthermore, the trend towards mega-farms of more than a million birds must be stopped.

To avoid the worst consequences of this virus, we must look at its primary Source: the incubator that is intensive poultry farming.The Conversation



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