Commonground
Senior Moderator
5/4/2024 Viet Nam Department of Animal Health (DAH), and the Food and Agriculture Organization of the United Nations (FAO) urge the public to keep vigilance on the Highly Pathogenic Avian Influenza (HPAI) A(H5N1) upon the detection of new re- assorted HPAI A(H5N1) viruses in chickens and muscovy ducks through active surveillance in Viet Nam.
There has been dominance of influenza A(H5N1) clade 2.3.4.4b virus circulation around the world since 2021. Avian influenza A - H5N2, H5N4, H5N5, H5N6 and H5N8 subtypes have all been sporadically detected in poultry or wild birds. From December 2023 to February 2024, at least 646 HPAI outbreaks have been reported in five geographic regions caused mainly by A(H5N1) (610). In Asia, several clades continue to circulate, including A(H5N1) 2.3.4.4b, 2.3.2.1c and others, which can lead to reassortment and the appearance of viruses with new characteristics. A novel reassortant influenza A(H5N1) virus has been detected across the Greater Mekong Subregion (GMS), causing infections in both humans and poultry since mid- 2022. This virus has recently caused human outbreaks in Cambodia early this year. This virus contains the surface proteins from clade 2.3.2.1c that has circulated locally, but internal genes from a more recent clade 2.3.4.4b virus. The introduction and widespread circulation of this reassortant influenza A(H5N1) virus into the GMS poses a significant risk to both animal and human health, given the historical impact of HPAI outbreaks in the region. Further, this reassortment event indicates not only the adaptive capacity of the virus but also the ever-present risk of the emergence of new, potentially more virulent strains.
In Vietnam, HPAI A(H5N1) viruses persist among poultry, albeit with sporadic outbreaks. Active surveillance across the country indicates circulation of HPAI A(H5) virus in recent years. Poultry vaccination against HPAI A(H5) viruses has been a crucial strategy in Vietnam's HPAI control efforts. Phylogenetic examination of HPAI A(H5N1) viruses sampled from live poultry markets and outbreaks between January 2022 and December 2023 revealed continued circulation of both clades 2.3.2.1c and 2.3.4.4b in Vietnam. Clade 2.3.2.1c predominantly circulated in southern Vietnam, while clade 2.3.4.4b was found nationwide. A small number of HPAI A(H5N1) viruses detected in live poultry markets in the southern provinces collected in 2023 exhibited reassortment between clade 2.3.2.1c and 2.3.4.4b genes, however no PB2-E627K substitution was detected.
continued: https://www.fao.org/vietnam/news/detail-events/en/c/1680337/
There has been dominance of influenza A(H5N1) clade 2.3.4.4b virus circulation around the world since 2021. Avian influenza A - H5N2, H5N4, H5N5, H5N6 and H5N8 subtypes have all been sporadically detected in poultry or wild birds. From December 2023 to February 2024, at least 646 HPAI outbreaks have been reported in five geographic regions caused mainly by A(H5N1) (610). In Asia, several clades continue to circulate, including A(H5N1) 2.3.4.4b, 2.3.2.1c and others, which can lead to reassortment and the appearance of viruses with new characteristics. A novel reassortant influenza A(H5N1) virus has been detected across the Greater Mekong Subregion (GMS), causing infections in both humans and poultry since mid- 2022. This virus has recently caused human outbreaks in Cambodia early this year. This virus contains the surface proteins from clade 2.3.2.1c that has circulated locally, but internal genes from a more recent clade 2.3.4.4b virus. The introduction and widespread circulation of this reassortant influenza A(H5N1) virus into the GMS poses a significant risk to both animal and human health, given the historical impact of HPAI outbreaks in the region. Further, this reassortment event indicates not only the adaptive capacity of the virus but also the ever-present risk of the emergence of new, potentially more virulent strains.
In Vietnam, HPAI A(H5N1) viruses persist among poultry, albeit with sporadic outbreaks. Active surveillance across the country indicates circulation of HPAI A(H5) virus in recent years. Poultry vaccination against HPAI A(H5) viruses has been a crucial strategy in Vietnam's HPAI control efforts. Phylogenetic examination of HPAI A(H5N1) viruses sampled from live poultry markets and outbreaks between January 2022 and December 2023 revealed continued circulation of both clades 2.3.2.1c and 2.3.4.4b in Vietnam. Clade 2.3.2.1c predominantly circulated in southern Vietnam, while clade 2.3.4.4b was found nationwide. A small number of HPAI A(H5N1) viruses detected in live poultry markets in the southern provinces collected in 2023 exhibited reassortment between clade 2.3.2.1c and 2.3.4.4b genes, however no PB2-E627K substitution was detected.
continued: https://www.fao.org/vietnam/news/detail-events/en/c/1680337/
