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. 2026 Feb 1;105(4):106580.
doi: 10.1016/j.psj.2026.106580. Online ahead of print.

Research note: Molecular characteristics and genetic evolution of H1N1 avian influenza virus from wild birds in Shanghai, China

Ling Tang  1 , Rui Wang  1 , Guimei He  2
Affiliations

Research note: Molecular characteristics and genetic evolution of H1N1 avian influenza virus from wild birds in Shanghai, China

Ling Tang et al. Poult Sci. .

Abstract

The H1N1 influenza virus is a major pandemic and seasonal pathogen with a broad host range, posing a substantial threat to human health and underscoring the need for continuous surveillance. Wild birds, as natural reservoirs of avian influenza viruses (AIVs), carry H1N1 strains capable of reassorting with other influenza viruses, which can drive pandemic emergence. The global migration of wild birds facilitates the spread of these viruses, and their interactions with poultry increase the risk of cross-species transmission, further amplifying the public health threat. However, knowledge of H1N1 genetic diversity in wild birds remains limited. Database analysis shows 80% of avian-origin H1N1 isolates come from wild birds across over 40 countries, mainly in North America, Europe and Asia. This study characterized the molecular traits and genetic evolution of four H1N1 AIVs isolated from common teal and spot-billed ducks during 2019-2021. Phylogenetic and sequence analyses revealed these viruses cluster into distinct lineages, divergent from mammalian H1N1 strains, with complex genetic origins involving frequent recombination and high diversity. Frequent wild bird-poultry transmission elevates zoonotic risks. Our findings highlight wild birds' critical role in H1N1 transmission and confirm their role as an H1N1 gene pool, emphasizing the need for sustained monitoring and research.

Keywords: Avian influenza virus; H1N1 subtype; Molecular characteristics; Phylogenetic analysis; Wild bird.

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Conflict of interest statement

Disclosures The authors declare that the research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest.

Figures

Fig. 1 dummy alt text
Fig. 1
Spatial and temporal distribution of global H1N1 isolates. (a)-(d) Proportion chart of H1N1 isolates classified by different hosts. (e) The global distribution of H1N1 isolates in human and avian species. Map generated using ArcGIS version 10.2. Size of each circle represents the number of isolates and the legend circle represents 300 isolates. The shades of orange represent the number of H1N1 isolates from human in different countries. Red, blue, green, and yellow colors represent the number of H1N1 isolates from wild duck, duck, chicken, and other avian, respectively. (f) Number of H1N1 isolates from wild birds in the world from 1976 to 2024.
Fig. 2 dummy alt text
Fig. 2
Phylogeny of HA and NA genes of H1N1 isolates. In the phylogenetic tree, HA genes (c, n = 479) and NA genes (d, n = 435) sequences were respectively classified into different gene groups. The size of the pink circle indicated neighbour-joining bootstrap values, values less than 75% were not shown. Four H1N1 isolates characterized in this study are indicated by red five stars. The region and host information of major clades are labeled in different colors next to the phylogenetic tree.
See this image and copyright information in PMC

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