Background
In late 2023, the first human case caused by an H10N5 avian influenza virus (AIV) was diagnosed in China. H10Ny AIVs have been identified in various poultry and wild birds in Eurasia, the Americas, and Oceania.
Methods
We analyzed the clinical data of the H10N5 AIV-infected patient, isolated the virus, and evaluated the virus receptor-binding properties together with the H10N8 and H10N3 AIVs identified in humans and poultry. The genomic data of the human-infecting H10N5 strain and avian H10Ny AIVs (n = 48, including 16 strains of H10N3 and 2 strains of H10N8) from live poultry markets in China, during 2019–2021, were sequenced. We inferred the genetic origin and spread pattern of the H10N5 AIV using the phylodynamic methods. In addition, given all available nucleotide sequences, the spatial-temporal dynamics, host distribution, and the maximum-likelihood phylogenies of global H10 AIVs were reconstructed.
Findings
The first H10N5 AIV-infected human case co-infected with seasonal influenza H3N2 virus was identified. Unfortunately, the patient died after systematic treatments. The H10N5 virus predominantly bound avian-type receptor, without any known mammalian-adapted mutations. Phylodynamic inference indicated that the H10N5 AIV was generated by multiple reassortments among viruses from Korea and Japan, central Asia, and China in late 2022, acquiring the seven gene segments from H10N7 or other low pathogenic AIVs in wild Anseriformes, except for the PA gene from H5N2 AIVs in Domestic Anseriformes. The HA gene of the H10N5 virus belongs to the North American lineage, which was probably introduced into Asia by migratory birds, subsequently forming local circulation.
Interpretation
Unlike the human-infecting H10N3 and H10N8 AIVs acquiring six internal protein-coding genes from H9N2 AIVs in domestic poultry, the human-infecting H10N5 AIV was generated through multiple reassortments among viruses mainly carried by wild Anseriformes. Furthermore, worldwide distribution, inter-continental transmission, and genetic exchanges between Eurasian and North American lineages call for more concerns about influenza surveillance on H10Ny AIVs, especially in the flyway overlapping areas.