case_images: PMC11682823_01
case_images: Evolutionary origins of isolate A/Victoria/149/2024(H5N1) (red circles and bold text) in study of influenza A(H5N1) virus clade 2.3.2.1a in traveler returning to Australia from India, 2024. A) Reassortant origins of A/Victoria/149/2024 based on analysis of each segment; detailed phylogenies for all segments are provided in Appendix Figure 1). B-D) Maximum-likelihood trees for HA (B), PB2 (C), and M (D) genes with a sample of BLAST-matched sequences (https://blast.ncbi.nlm.nih.gov). Bootstrap values >90% for key nodes are shown. Scale bars indicate number of nucleotide substitutions per site for each gene. HA, hemagglutinin; LPAI, low pathogenicity avian influenza; M, matrix protein; NP, nucleoprotein; NS, nonstructural; PA, polymerase acidic; PB1, polymerase basic 1; PB2, polymerase basic 2.
case_images: 24-1210-F1.jpg
case_images: PMC11682823_01_24-1210-F1.jpg
case_images: F1
case_images: Figure 1). Four segments (HA, neuraminidase [NA], nucleoprotein, and nonstructural) were most similar to clade 2.3.2.1a viruses circulating in Bangladesh (Appendix Those results mirror the features of the 2021 H5N1 human case in India (Figure 1, panel A), including the multiple basic amino acid cleavage site with only 1 change (HA R323K); both cases lacked classic mammalian adaptations.
case_images: Numbers and diversity of highly pathogenic avian influenza A(H5Nx) virus isolates reported in South and East Asia in GISAID (https://www.gisaid.org) during January 1, 2020-July 29, 2024. Pie charts for India and Bangladesh, the only 2 countries in which clade 2.3.2.1a hemagglutinin sequences (light green, arrow) have been deposited into GISAID, have been enlarged.
case_images: 24-1210-F2.jpg
case_images: PMC11682823_01_24-1210-F2.jpg
case_images: F2
case_images: Further analysis of the A/Victoria/149/2024 HA sequence on a maximum-clade credibility tree demonstrated that the virus diverged from the most closely related clade 2.3.2.1a HA sequences in GISAID in June 2020 (95% highest posterior density December 2019-January 2021) (Appendix Figure 2). During 2020-2024, only 322 H5 isolates were reported from South Asia (India, Pakistan, and Bangladesh) in GISAID; most arose from Bangladesh (n = 314) (Figure 2).