tetano
Editor, Senior Moderator
Proc Natl Acad Sci U S A
. 2026 Jul 7;123(27):e2400023123.
doi: 10.1073/pnas.2400023123. Epub 2026 Jun 29.
Genomic and structural evidence of SARS-CoV-2 and MERS-CoV in migratory birds
Jian Cao[SUP] #[/SUP][SUP] 1 2 [/SUP], Sheng Liu[SUP] #[/SUP][SUP] 3 4 [/SUP], Chao Su[SUP] #[/SUP][SUP] 1 [/SUP], Liang Wang[SUP] 1 [/SUP], Zhiyuan Li[SUP] 1 [/SUP], Jianxun Qi[SUP] 1 2 [/SUP], Peiyi Wang[SUP] 4 [/SUP], George F Gao[SUP] 1 [/SUP]
Affiliations
Migratory birds are the natural reservoir of influenza A virus (IAV), but their role as a carrier of SARS-CoV-2 remains unclear. Here, we report the identification of three almost full-length viral genome sequences of SARS-CoV-2 variants of concern (VOCs) in Tundra swans. These sequences are named hCoV-19/Tundra swan/Jiangxi/IMCAS_M1/2021 (IMCAS_M1), hCoV-19/Tundra swan/Jiangxi /IMCAS_M2/2021 (IMCAS_M2), and hCoV-19/Tundra swan/Jiangxi/IMCAS_M3/2021 (IMCAS_M3). IMCAS_M1 and IMCAS_M3 have the same mutations as the Beta VOC (K417N, E484K, and N501Y) in the receptor-binding domain (RBD) of the viral spike (S) protein, whereas IMCAS_M2 shares the same mutations as the Gamma VOC (K417T, E484K, and N501Y) in the RBD with all three showing their distinct mutations in the genomes. Virus receptor angiotensin-converting enzyme 2 (ACE2) proteins from both Tundra swan (tsACE2) and Black swan (bsACE2) can bind to the RBDs of all three viruses and the Alpha VOC, but not to RBD of the prototype (PT) virus. The polar contacts and hydrophobic interactions revealed by cryo-electron microscopy (cryo-EM) structures of the RBD-ACE2 complex, play key roles in virus-receptor engagement. Furthermore, HeLa cells expressing bsACE2 and tsACE2 proteins could be transduced by pseudotyped SARS-CoV-2 variants (Alpha, Beta, and Gamma) but not PT SARS-CoV-2. In addition, we obtained one partial genome of MERS-CoV named Bar-headed goose/Tibet/IMCAS_M4/2022 (IMCAS_M4) with 20,180 bp (~70.0% coverage). Our findings highlight the importance of migratory birds as potential carrier of both SARS-CoV-2 and MERS-CoV, thereby posing potential threat to public health.
Keywords: MERS-CoV; SARS-CoV-2; Tundra swan; genome; migratory birds.
. 2026 Jul 7;123(27):e2400023123.
doi: 10.1073/pnas.2400023123. Epub 2026 Jun 29.
Genomic and structural evidence of SARS-CoV-2 and MERS-CoV in migratory birds
Jian Cao[SUP] #[/SUP][SUP] 1 2 [/SUP], Sheng Liu[SUP] #[/SUP][SUP] 3 4 [/SUP], Chao Su[SUP] #[/SUP][SUP] 1 [/SUP], Liang Wang[SUP] 1 [/SUP], Zhiyuan Li[SUP] 1 [/SUP], Jianxun Qi[SUP] 1 2 [/SUP], Peiyi Wang[SUP] 4 [/SUP], George F Gao[SUP] 1 [/SUP]
Affiliations
- PMID: 42372155
- DOI: 10.1073/pnas.2400023123
Migratory birds are the natural reservoir of influenza A virus (IAV), but their role as a carrier of SARS-CoV-2 remains unclear. Here, we report the identification of three almost full-length viral genome sequences of SARS-CoV-2 variants of concern (VOCs) in Tundra swans. These sequences are named hCoV-19/Tundra swan/Jiangxi/IMCAS_M1/2021 (IMCAS_M1), hCoV-19/Tundra swan/Jiangxi /IMCAS_M2/2021 (IMCAS_M2), and hCoV-19/Tundra swan/Jiangxi/IMCAS_M3/2021 (IMCAS_M3). IMCAS_M1 and IMCAS_M3 have the same mutations as the Beta VOC (K417N, E484K, and N501Y) in the receptor-binding domain (RBD) of the viral spike (S) protein, whereas IMCAS_M2 shares the same mutations as the Gamma VOC (K417T, E484K, and N501Y) in the RBD with all three showing their distinct mutations in the genomes. Virus receptor angiotensin-converting enzyme 2 (ACE2) proteins from both Tundra swan (tsACE2) and Black swan (bsACE2) can bind to the RBDs of all three viruses and the Alpha VOC, but not to RBD of the prototype (PT) virus. The polar contacts and hydrophobic interactions revealed by cryo-electron microscopy (cryo-EM) structures of the RBD-ACE2 complex, play key roles in virus-receptor engagement. Furthermore, HeLa cells expressing bsACE2 and tsACE2 proteins could be transduced by pseudotyped SARS-CoV-2 variants (Alpha, Beta, and Gamma) but not PT SARS-CoV-2. In addition, we obtained one partial genome of MERS-CoV named Bar-headed goose/Tibet/IMCAS_M4/2022 (IMCAS_M4) with 20,180 bp (~70.0% coverage). Our findings highlight the importance of migratory birds as potential carrier of both SARS-CoV-2 and MERS-CoV, thereby posing potential threat to public health.
Keywords: MERS-CoV; SARS-CoV-2; Tundra swan; genome; migratory birds.