Genetic relatedness of hemagglutinins of the H1 subtype of influenza a viruses isolated from swine and birds

Multiple lineages of antigenically and genetically diverse influenza A virus co-circulate in the United States swine population

“…Thus, pig tracheal cells can be infected not only by human influenza viruses but also by avian viruses. It has been postulated that pigs may have been the intermediate host responsible for the genesis of the last two human pandemic viruses which were reassortants between human and avian viruses (Kawaoka et al, 1989;Scholtissek et al, 1983).…”

Molecular analysis of the haemagglutinin gene of an avian H1N1 influenza virus

“…Historically, it appears to have emerged as a 'new' antigen on the swine influenza-like virus of the Spanish influenza pandemic which caused more than 20 million deaths in 1918 to 1919 (Palese & Young, 1983). Influenza A viruses of the H1 subtype infect humans, pigs and birds (Easterday, 1975;Webster et al, 1984) and genetic and antigenic relationships have been demonstrated between the subtype H 1 HAs of viruses isolated from these hosts (Scholtissek et al, 1983;Hinshaw et al, 1984;Aymard et al, 1985;Austin & Webster, 1986). However, nucleotide and deduced amino acid sequence comparisons between subtype H1 HA genes of isolates from humans, birds and mammals have not been possible because, despite a plethora of sequence data on human isolates (Daniels et al, 1985;Raymond et al, 1986;Stevens et al, 1987;Cox et al, 1989), there is only one published sequence of a swine influenza-like H1 HA (Both et al, 1983) and none at all from avian isolates of this subtype.…”

Molecular events leading to the creation of a pandemic influenza virus

“…Samples collected from Mexico and USA reveal that this novel strain of swine origin is a result of reassortment between closely circulating Eurasian Swine and North American triple reassortant swine H1N2 virus. The gene segments encoding the proteins NA and M are genetically similar to the Eurasian swine isolate which was reported to enter the Eurasian swine population through wild ducks in 1979 [28]. It has since been confi ned to Eurasia and never been reported in North America.…”