The world is currently witnessing the largest outbreak of avian influenza, commonly known as bird flu, with experts warning that the virus is rapidly changing. While the risk to humans is currently low, the surge in bird flu cases among mammals is a cause for concern. Calls for countries to vaccinate their poultry are increasing in order to contain the spread of the virus.
Unprecedented Outbreak and Evolution of Bird Flu Virus:
Avian influenza, specifically the H5N1 virus, has been known to cause seasonal outbreaks since its emergence in 1996. However, in mid-2021, something changed, leading to a significant increase in its infectiousness. Richard Webby, a researcher at St Jude Children’s Research Hospital and head of a World Health Organization collaborating center studying influenza in animals, describes this as “absolutely” the largest outbreak of avian influenza ever recorded. The outbreaks are no longer confined to specific seasons and have spread to new areas, resulting in massive deaths among wild birds and the culling of millions of poultry.
A study published in the journal Nature Communications, led by Webby, reveals the rapid evolution of the virus as it spread from Europe to North America. The virus showed increased virulence upon reaching North America, causing more severe diseases. In an experiment involving a ferret, researchers found a significantly higher viral load in its brain when infected with the new strains of bird flu, suggesting a greater pathogenicity compared to previous strains.
Changing Dynamics and Concerns:
While the risk to humans remains low, experts are alarmed by the rising number of bird flu cases in mammals. Chile recently reported a substantial number of deaths among sea lions, penguins, otters, porpoises, and dolphins due to bird flu. Most mammals contract the virus by consuming infected birds. However, there are indications that the virus can now transmit between mammals, posing a potential risk for human transmission.
Ian Brown, the head of virology at the UK’s Animal and Plant Health Agency, highlights that there is no clear evidence yet of sustained transmission of the virus in mammals. Nevertheless, the possibility of the virus adapting to humans cannot be ignored. Avian viruses bind to different receptors on host cells than human viruses, which has limited their ability to infect humans. However, experts warn that with a few minor genetic changes, the virus could become more adapted to human hosts, increasing the risk of human-to-human transmission.
The Importance of Vaccinating Poultry:
To curb the spread of bird flu and reduce the risk to humans, experts emphasize the need to vaccinate poultry. Some countries, including China, Egypt, and Vietnam, have already implemented vaccination campaigns. However, many nations have been reluctant due to import restrictions and concerns that vaccinated birds may still become infected. In the United States, several vaccine candidates for birds are currently undergoing testing, while France aims to commence poultry vaccination in the upcoming autumn.
Christine Middlemiss, the UK’s chief veterinary officer, acknowledges that vaccination is not a foolproof solution, as the virus continues to evolve. However, she suggests that traditionally reluctant countries should consider vaccinating poultry more frequently to mitigate the risk. Monique Eloit, the director general of the World Organisation for Animal Health, emphasizes the need to prioritize poultry vaccination, as the threat of a pandemic is no longer a mere fantasy but a potential reality.
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The ongoing outbreak of avian influenza presents a significant challenge as the virus rapidly evolves and spreads among birds and mammals. While the risk to humans remains low, the increasing number of cases among mammals raises concerns about potential human transmission. Vaccinating poultry is seen as a crucial step in reducing bird flu cases and minimizing the risk to humans. As the world faces the largest outbreak in history, it is imperative to prioritize vigilance, research, and proactive measures to effectively contain the spread of the virus and protect public health.
