Mainly marked by the rampant spread of a new coronavirus, the year 2020 also saw the explosion of another deadly pathogen that could pose a threat to global public health.
A strain that worries
Highly pathogenic avian influenza virus subtype, strain H5N8 was originally identified decades ago, but during the year 2020 a series of emerging and continuing outbreaks H5N8 in bird populations in dozens of countries has resulted in the death or culling of millions of birds worldwide.
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« The geographic regions affected have continued to expand and at least 46 countries have reported outbreaks of the highly pathogenic H5N8 virus “, Write the researchers Weifeng Shi and George F. Gao in a new article published in Science, highlighting the danger the virus would pose if it got out of control.
If the animals most vulnerable to H5N8 birds remain (in particular farmed chickens and ducks, but also wild and migratory birds), cases of transmission of the virus to humans have also been reported in recent months.
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In December 2020, an avian influenza epidemic broke out in Russiaand affected workers in the poultry industry. Seven people working on a farm in the south of Russiahad shown signs of infection. While these were the first human cases identified for the H5N8, it was certainly not a first for the clades and subclades linked to the H5N8, nor for the avian influenza virus in general.
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« To date, a total of 862 laboratory-confirmed human cases of H5N1 infection have been reported to the WorldHealth Organization (WHO), including 455 deaths », Explain Shi and Gao. « These cases originated from 17 countries, of which around 76% were from Egypt and Indonesia. »
Signs of constant evolution
But zoonotic risks are only part of the problem posed by H5N8 and his ilk. In most recent epidemics, a clade of H5N8 called 2.3.4 has become the dominant pathogen worldwide, first observed in a Chinese wet market in 2010.
« H5 avian viruses of the 2.3.4 clade, in particular the H5N8 subtype, have clearly shown a propensity to spread rapidly worldwide in migratory birds Write the researchers, who note that these viruses are also showing signs of constant evolution, genetically reassorting with parts of other avian virus subtypes.
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Shi and Gao, respectively from the First Medical University of Shandong and the Chinese Center for Disease Control and Prevention, were among the first scientists to document the novel coronavirus in early 2020. They note that the pandemic of Covid-19 that followed (and the prevention and control measures adopted by the world’s populations as a result) resulted in a sharp reduction in the spread of seasonal human influenza A and B viruses over the past year.
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Nevertheless, during the same period, a number of highly pathogenic avian viruses H5Ny, whose subtypes H5N1, H5N2, H5N5 and H5N8, have spread in China, on South Africa or in Europe.
Special adaptations in terms of cell binding
At the same time, research has shown that viruses of the 2.3.4 clade exhibit particular adaptations in cell binding that could induce greater risks in terms of transmission to humans, including potential transmissibility to humans. to human.
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Overall, the researchers say there is a need to dramatically strengthen our surveillance of avian influenza viruses in poultry farms, before these pathogens get out of hand.
« Due to the long-distance migration of wild birds, the innate tendency to reassortment of avian influenza viruses, the increased binding capacity to human-type receptors, and the constant antigenic variation of highly pathogenic forms, it is imperative not to ignore the global spread and potential risk of the H5N8 virus to poultry, bird life and global public health », Conclude the researchers.
