- Brown I, Ludwig S, Olsen C, Hannoun C, Scholtissek C, Hinshaw V, et al. Antigenic and genetic analyses of H1N1 influenza A viruses from European pigs. J Gen Virol. 1997;78 ( Pt 3):553-62 pubmed..Genetic analyses of two recent 'avian-like' swine viruses indicated that all the RNA segments are related most closely to those of avian influenza A viruses. ..