Sustained cross-species transmission of gammacoronavirus in wild birds reveled by viral characterization in China

Gammacoronavirus ({gamma}-CoV) primarily infects poultry, wild birds, and marine mammals. The widespread distribution and circulation of {gamma}-CoV in the ecological environment may lead to sustained transmission and economic loss. To better understand the diversity of {gamma}-CoV in wild birds, we collect 482 wild-bird fecal samples from Yunnan, encompassing fourteen bird species. We detected twelve {gamma}-CoV positive samples in five bird species, with the characterization of five complete genomes - HNU5-1, HNU5-2, HNU5-3, HNU6-1, and HNU6-2-indicating that these genomes represent two viral species. The HNU5 strains were derived from Black-headed gull (Chroicocephalus ridibundus), while the HNU6 strains were came from Mallard (Anas platyrhynchos), and both of those were recombinant. The HNU5 strain exhibited the highest sequence identity (95.45%) with a {gamma}-CoV strain isolated from Numenius phaeopus (GenBank accession: PP845452). Similarly, the HNU6 strain showed 95.18% nucleotide identity with a {gamma}-CoV strain (GenBank accession: PP845437) derived from Anas platyrhynchos. Taxonomic analysis confirmed that HNU6s belong to the Gammacoronavirus anatis species, while HNU5s attributed to a new species. Cross-species analysis revealed active host-switching events among {gamma}-CoVs, indicating potential transmission of {gamma}-CoVs from marine mammals to wild bird, from wild bird to poultry, and inter-wild bird and inter-poultry transmission. In summary, we report five new {gamma}-CoV strains in wild birds and outline the cross-species transmission of {gamma}-CoVs. Our findings link {gamma}-CoV hosts across different natural environments and provide new insights for exploring {gamma}-CoVs.