Biological features of human influenza A(H3N8) viruses in China.

Influenza A(H3N8) viruses first emerged in humans in 2022, but their public health risk has not been evaluated. Here, we systematically investigated the biological features of avian and human isolated H3N8 viruses. The human-origin H3N8 viruses exhibited dual receptor binding profiles but avian-origin H3N8 viruses bound to avian type (sialic acid α2, 3) receptors only. All H3N8 viruses were sensitive to the antiviral drug oseltamivir. Although H3N8 viruses showed lower virulence than the 2009 pandemic H1N1 (09pdmH1N1) viruses, they induced comparable infectivity in mice. More importantly, the human population is naïve to H3N8 virus infection and current seasonal vaccination is not protective. Therefore, the threat of influenza A(H3N8) viruses should not be underestimated. Any variations should be monitored closely and their effect should be studied in time for the pandemic potential preparedness purpose.