Genetic Characteristics and Pathogenicity of Recent G4 Eurasian Avian-like H1N1 Swine Influenza Viruses in China

Abstract

Simple Summary Swine influenza viruses can cause respiratory disease in pigs and may occasionally infect humans, making their continued monitoring important for both animal and public health. In this study, six recently detected Eurasian avian-like H1N1 swine influenza viruses collected from pigs in different regions of China between 2023 and 2025 were examined. Genetic analysis showed that these viruses belonged to an established group that has circulated in Chinese pigs for several years, while several changes were found in proteins involved in immune recognition and attachment to host cells. Antibodies that reacted with one representative virus were detected in serum samples collected from pigs in multiple regions. This representative virus also replicated efficiently and caused respiratory disease and lung lesions in experimentally infected pigs. These findings show that this group of swine influenza viruses continues to circulate and change in pig populations, supporting the need for continued monitoring of their genetic, antigenic, and biological characteristics.