The authors designed a universal primer set for the full-length amplification of all influenza A viruses, aiming to systematically identify and analyze the 15 HA and 9 NA subtypes. The primers were based on conserved terminal segments of the genomic viral RNA, which are unique to each segment. The set of primers successfully amplified all eight segments of N1, N2, N4, N5, and N8 subtypes. For N3, N6, N7, and N9 subtypes, which have different neuraminidase gene sequences, the primer design was optimized to allow amplification of these genes as well. The resulting primer set is suitable for generating full-length cDNAs, subtyping viruses, sequencing their DNA, and constructing expression plasmids for reverse genetics systems. The study demonstrates the effectiveness of this RT-PCR method for characterizing all influenza A virus subtypes and highlights its potential in rapid identification and characterization of influenza viruses.The authors designed a universal primer set for the full-length amplification of all influenza A viruses, aiming to systematically identify and analyze the 15 HA and 9 NA subtypes. The primers were based on conserved terminal segments of the genomic viral RNA, which are unique to each segment. The set of primers successfully amplified all eight segments of N1, N2, N4, N5, and N8 subtypes. For N3, N6, N7, and N9 subtypes, which have different neuraminidase gene sequences, the primer design was optimized to allow amplification of these genes as well. The resulting primer set is suitable for generating full-length cDNAs, subtyping viruses, sequencing their DNA, and constructing expression plasmids for reverse genetics systems. The study demonstrates the effectiveness of this RT-PCR method for characterizing all influenza A virus subtypes and highlights its potential in rapid identification and characterization of influenza viruses.