In recent decades, dozens of countries across the world have seen cases of poultry and wild birds falling sick with influenza A H5N8, a highly pathogenic avian influenza virus (AIV). The subtype of flu was not generally associated with human infections, but that changed in February 2021 when seven poultry farm workers in southern Russia became the first documented human cases of H5N8 bird flu.
Writing in Science, scientists from the Chinese Center for Disease Control and Prevention and Shandong First Medical University warn that H5N8 has demonstrated that it can leap from species to species and holds the potential to erupt into a “disastrous pandemic".
"At least 46 countries have reported highly pathogenic H5N8 AIV outbreaks," the researchers write. "The global spread of AIVs, particularly the H5N8 subtype, has become a major concern to poultry farming and wildlife security but, critically, also to global public health."
Avian flu strains are able to hop around the world through the migration of wild birds. If the virus then manages to make its way into a poultry farm, an outbreak can easily take root, often resulting in the death or culling of millions of birds. The “strain” of the virus that emerged in Russia belongs to H5N8 AIV clade 126.96.36.199.b, which is a branch on the family tree of clade 2.3.4. The clade 2.3.4 was first isolated from a domestic duck at a wet market in Jiangsu, China in 2010 and has become increasingly dominant across the world in the past two decades.
After first being picked up in Jiangsu, routine surveillance studies then showed the clade started to spring up in neighboring countries before eventually making its way to wider Asia and Europe. Outbreaks among birds have now been seen across the world, including the US, the UK, mainland Europe, India, Israel, South Korea, Mongolia, China, Japan, Russia, Nigeria, South Africa, and more.
As mentioned, there have only been a very small number of cases in humans. In the case of the recent Russian outbreak, all the patients remained asymptomatic, according to the World Health Organization. While there was some speculation that human-to-human transmission may occur, health authorities currently say the risk of this is low.
As per the new paper in Science, H5N8 has the potential to cause serious trouble for global public health. However, it isn’t all bad news. The researchers argue that there is still the opportunity to prevent a potential H5N8 pandemic. COVID-19 has brought the always existing threat of a global virus outbreak into very real terms and helped to refine much of the world’s measures to control and contain disease outbreaks. But this shouldn't make us complacent. To negate the risk of H5N8 and other potentially troublesome flu strains, they argue, the world needs to see major changes to agriculture, as well as the surveillance of emerging diseases.