The mutation found in the PB2 gene is T271A. In vitro studies suggest that H5N1 viruses with this mutation can more easily infect humans.
An outbreak of H5N1 bird flu at a farm in A Coruña forced the culling of more than 50,000 mink
In the first week of October 2022, a sharp increase in mortality of American mink was identified (NeoVision Vision) raised on a Galician farm in the municipality of Caral in the province of A Coruña. The analysis revealed that the animals were affected by an outbreak of highly pathogenic H5N1 avian influenza (HPAI). The origin of the outbreak is unknown, but it is likely that wild birds were involved in bringing the virus to the farm, because The onset of symptoms in mink coincided with a wave of H5N1 infections in seabirds. in Galicia
Mink census amount on the farm over 51,000 copies, On November 17, 2022, all mink at the infected facility were euthanized and all carcasses, fomites and debris destroyed.
Recent analyzes have shown that the influenza A H5N1 virus involved in the outbreak belongs to the 18.104.22.168b clade, which is currently circulating in Europe. The H5N1 highly pathogenic avian influenza virus is capable of infecting many mammals, including foxes, dogs, cats, tigers, leopards, bears or raccoons, but This is the first time that infection by an H5N1 virus of clade 22.214.171.124b has been detected in Europe, which are found in minks bred to sell their fur.
In fact, the ancestral reservoir of all influenza A viruses, including H5N1, are waterfowl, specifically those in the order Anseriformes, which includes swans or ducks, and the order Charadriiformes, where seagulls belong. All known influenza pandemics have been caused by the influenza A virus. Influenzavirus A is responsible only for bird flu, as well as the causative agent of common flu in humans and swine and equine flu.
dozens of possible combinations
In influenza virus A High mutation rates and a phenomenon known as genetic shuffling are what allow the virus to generate many different combinations. Type A influenza viruses can be divided into different subtypes based on the genes that make up the surface proteins, hemagglutinin (H) and neuraminidase (N). The hemagglutinin (H) and neuraminidase (N) proteins of the virus are the main sites of antigen recognition by the host’s immune system. There are 18 different hemagglutinin subtypes and 11 neuraminidase subtypes, from H1 to H18 and N1 to N11, respectively, so there can be dozens of influenza A subtype combinations, H5N1 being one of them. It is noteworthy that within each subtype there is considerable genetic, antigenic and phenotypic variation, which affects the pathogenicity of the strain.
What is the danger to humans?
The persistence of highly pathogenic H5N1 virus in wild birds since the pandemic wave of the 2020–2021 season indicates that May be endemic in wild bird populations in Europe, This implies that there is a significant risk to the health of birds, humans and European wildlife as the virus is present throughout the year with the greatest risk in the autumn and winter months.
In fact, The lethality of H5N1 virus in humans is more than 50%. Fortunately, bird-to-human transmission is rare and sustained person-to-person transmission has not been observed.
a new mutation
However, a recent report published on January 19, 2023 warns that the viruses found in mink farms are different from all H5N1 viruses of the 126.96.36.199b clade because they have A rare mutation (T271A) in the PB2 gene, which may have public health implications. In fact, the same mutation is present in the avian-type PB2 gene of the 2009 pandemic swine-origin influenza A (H1N1) virus (H1N1pdm). This mutation could have arisen de novo in the mink, but it cannot be ruled out that it is circulating in avian populations.
Unfortunately, H5N1 viruses with the T271A mutation in the PB2 gene show growth in mammalian cells in vitro, which indicate that they can more easily infect humans. Direct infection of humans with highly pathogenic H5N1 avian influenza virus suggests that viral mutation is a mechanism for the emergence of novel human influenza A viruses.
Most human-pathogenic influenza virus subtypes originate from birds and pigs. The latter is considered an ideal recombination vessel for variants of different origins. Now, experimental and field evidence has shown that mink are susceptible and permissive to avian and human influenza A viruses, which can lead to dangerous conditions, such as This species may serve as a potential mixing vessel for transmission between birds, mammals and humans. Therefore, it is prudent to strengthen surveillance systems in mink farms to prevent and control the incidence of disease transmission from mink to workers and vice versa.
Today, H5N1 bird flu represents a major pandemic threat, both because it causes severe disease in humans, and because there is a possibility that bird flu viruses can mutate and spread more easily from person to person. Can get the ability to spread from.