PDF(Pubmed)
Abstract：
In 2023, South Africa continued to experience sporadic cases of clade 2.3.4.4b H5N1 high-pathogenicity avian influenza (HPAI) in coastal seabirds and poultry. Active environmental surveillance determined that H5Nx, H7Nx, H9Nx, H11Nx, H6N2, and H12N2, amongst other unidentified subtypes, circulated in wild birds and ostriches in 2023, but that H5Nx was predominant. Genome sequencing and phylogenetic analysis of confirmed H5N1 HPAI cases determined that only two of the fifteen sub-genotypes that circulated in South Africa in 2021-2022 still persisted in 2023. Sub-genotype SA13 remained restricted to coastal seabirds, with accelerated mutations observed in the neuraminidase protein. SA15 caused the chicken outbreaks, but outbreaks in the Paardeberg and George areas, in the Western Cape province, and the Camperdown region of the KwaZulu-Natal province were unrelated to each other, implicating wild birds as the source. All SA15 viruses contained a truncation in the PB1-F2 gene, but in the Western Cape SA15 chicken viruses, PA-X was putatively expressed as a novel isoform with eight additional amino acids. South African clade 2.3.4.4b H5N1 viruses had comparatively fewer markers of virulence and pathogenicity compared to European strains, a possible reason why no spillover to mammals has occurred here yet.
摘要：
2023年，南非继续在沿海海鸟和家禽中发生零星的进化枝2.3.4.4bH5N1高致病性禽流感（HPAI）病例。积极的环境监测确定H5Nx，H7Nx,H9Nx,H11Nx,H6N2和H12N2，以及其他身份不明的亚型，2023年在野生鸟类和鸵鸟中传播，但H5Nx占主导地位。对已确认的H5N1HPAI病例的基因组测序和系统发育分析确定，2021-2022年在南非传播的15种亚基因型中，只有2种在2023年仍然存在。SA13亚型仍然限于沿海海鸟，在神经氨酸酶蛋白中观察到加速突变。SA15引起了鸡肉的爆发，但是帕尔德贝格和乔治地区的疫情爆发，在西开普省，和夸祖鲁-纳塔尔省的坎珀顿地区互不相关,暗示野生鸟类是源头。所有SA15病毒在PB1-F2基因中都含有截短，但是在西开普SA15鸡病毒中，PA-X被推定表达为具有八个额外氨基酸的新型同种型。与欧洲毒株相比，南非进化枝2.3.4.4bH5N1病毒的毒力和致病性标记相对较少，这可能是为什么这里还没有向哺乳动物溢出的原因。
