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Abstract The introduction and subsequent detection of highly pathogenic avian influenza (HPAI) in poultry is influenced by the virus replication fitness, transmission fitness, and virulence in poultry. These viral fitness parameters are important for implementing surveillance and control measures for poultry. This study investigates the potential application of an avian in vitro model using primary chicken embryo (CEF) and duck embryo fibroblasts (DEF) to identify the viral fitness for a reference panel of eight dominant HPAI clade 2.3.4.4 virus genotypes : four H5N1 viruses isolated between 2021 and 2024, as well as three H5N8 and one H5N6 virus isolated between 2014 and 2020. Infectious virus titre and cytopathogenicity were measured in the primary cell cultures over time and these data were analysed using a mathematical model which delineates cell populations into susceptible, latent, infectious, and dead compartments. In addition to obtaining traditional virological parameters such...

Abstract In November 2022, we reported a fatal case of human infection caused by a highly pathogenic avian influenza A(H5N6) virus bearing a clade 2.3.4.4b HA gene in Changsha City . We investigated the transmission route and distribution of the H5N6 virus in the largest live-poultry market (LPM), which is linked to the human infection. A total of 1357 samples from the LPM were collected for avian influenza A virus detection from 2020 to 2023. The proportion of LPM samples positive for H5 subtype avian influenza virus was 14.30% (194/1357). Sequences of H5N6 (n = 10) and H5N1 (n = 4) avian influenza viruses were obtained from the LPM samples using next-generation sequencing. The complete genome sequence of the H5N6 virus from the human infection case, A/Changsha/1/2022(EPI_ISL_16466440), was determined and analyzed. The PB1 and PB2 segments shared 99.65% and 99.23% sequence identity with A/duck/Hunan/S40199/2021(H5N6) and A/Whooper swan/Sanmenxia/H615/2020(H5N8), respectively. The othe...

February 2025  The development of influenza candidate vaccine viruses (CVVs),  coordinated by WHO, remains an essential component of the overall global  strategy for influenza pandemic preparedness . Selection and development of  CVVs are the first steps towards timely vaccine production and do not imply a  recommendation for initiating manufacture. National authorities may consider the  use of 1 or more of these CVVs for pilot lot vaccine production, clinical trials and  other pandemic preparedness purposes based on their assessment of public health  risk and need. Zoonotic influenza viruses continue to be identified  and evolve both antigenically and genetically, leading to the need for additional  CVVs for pandemic preparedness purposes. Changes in the antigenic and genetic  characteristics of these viruses relative to existing CVVs and their potential risks  to public health justify the need to develop new CVVs. This docume...

FAO calls for increased vigilance and preparedness for avian influenza (AI) during the traditional New Year festivities that will take place across Asia on the week of 27 January 2025 . In the past year, outbreaks of AI have continued to be reported in domestic poultry, wild birds and mammals in Asia . Several AI virus subtypes including H5N1, H5N2, H5N3, H5N5, H5N6, H5N8, H7N3, H7N6, H7N8, H7N9, H10N5 , and H3N2 are currently well-established in both wild and domestic bird populations in the region. In addition, subtype H5N1 subclade 2.3.4.4b continues to circulate in both wild and domestic birds worldwide. Highly pathogenic avian influenza (HPAI) can lead to heavy losses for the poultry industry, in particular to the livelihoods of vulnerable small-scale producers . Poultry trade and related activities play a key role in AI spread and amplification in domestic bird populations, including the trade of infected live poultry and their products, handling or slaughtering infected poultry,...

{Excerpt} Dear Editor, The highly pathogenic avian influenza viruses (HPAIVs) are important epizootic and zoonotic pathogens that cause significant economic losses to the poultry industry and pose a serious risk to veterinary and public health . Wild birds have been recognized as the primary reservoirs for influenza A virus, and some species show little sign of clinical disease or even can be asymptomatic during long distance carriers of the virus (Lycett et al., 2019). Since it was first discovered in 1959, the H5Nx HPAIVs have spread globally and cause outbreaks in wild birds, poultry and sporadic human and other mammalian infections (Lycett et al., 2019). Due to the reassortant events of diverse strains facilitated by migratory waterfowl, the clade 2.3.4.4 of H5Nx viruses acquiring neuraminidase (NA) gene from other low pathogenicity avian influenza viruses (LPAIVs) emerged in 2014 and gradually became the dominant sub-clade (Lee et al., 2017). The genetic diversity of clade 2.3.4.4...

Abstract During the 2023–2024 winter, 11 high pathogenicity avian influenza (HPAI) outbreaks caused by clade 2.3.4.4b H5N1 and H5N6 HPAI viruses were confirmed in Japanese domestic poultry among 10 prefectures (n = 10 and 1, respectively). In this study, we aimed to genetically and pathologically characterize these viruses. Phylogenetic analysis revealed that H5N1 viruses were classified into the G2d-0 genotype , whereas the H5N6 virus was a novel genotype in Japan, designated as G2c-12. The G2c-12 virus shared PB2, PB1, PA, HA, and M genes with previous G2c viruses , but had NP and NS genes originating from avian influenza viruses in wild birds abroad. The N6 NA gene was derived from an H5N6 HPAI virus that was different from the viruses responsible for the outbreaks in Japan in 2016–2017 and 2017–2018. Experimental infections in chickens infected with H5N1(G2d-0) and H5N6(G2c-12) HPAI viruses showed no significant differences in the 50% chicken lethal dose, mean death time, or virus ...