Acording to the CDC. the 1918 "Spanish Flu" is the original source of the n subtype of "Swine Flu" circulating now.
Fort Dix was not the origin. It seems Pigs are a mixing bowl for many virus's.
"Novel Swine Influenza Virus Subtype H3N1, United States"
"Influenza A virus infects various animal species and transmits among different hosts, especially between humans and swine. Swine may serve as a
mixing vessel to create new reassortants that could infect humans. Thus, monitoring and characterizing influenza viruses in swine are important in
preventing interspecies transmission. We report the emergence and characterization of a novel H3N1 subtype of swine influenza virus (SIV) in the
United States. Phylogenetic analysis showed that the H3N1 SIVs may have acquired the hemagglutinin gene from an H3N2 turkey isolate, the neuraminidase
gene from a human H1N1 isolate, and the remaining genes from currently circulating SIVs. The H3N1 SIVs were antigenically related to the turkey virus.
Lung lesions and nasal shedding occurred in swine infected with the H3N1 SIVs, suggesting the potential to transmit among swine and to humans. Further
surveillance will help determine whether this novel subtype will continue to circulate in swine populations.
Influenza A viruses infect many animal species including birds, seals, whales, humans, horses, and swine. Migrating waterfowl are the primordial
reservoir. They contain a gene pool of all subtypes of influenza A viruses (1), and phylogenetic analysis suggests that transmission of influenza A
virus among various species can occur. Interspecies transmission between humans and swine has been documented (1). Both human and swine influenza
viruses (SIVs) recognize sialyl α2,6-galactose oligosaccharide side chains as the receptor on the host cell surface (2,3). In addition, swine cells
also contain sialyl α2,3-galactose-linkage, the receptor for avian influenza viruses. Experimental and epidemiologic evidence demonstrates that
different subtypes of avian influenza viruses can replicate in swine (4–6). Therefore, swine can be a vessel for reassortment of human and avian
influenza viruses (7).
The viral structure that binds to the cellular receptor is the receptor-binding site, which is located on the globular part of the hemagglutinin (HA)
monomer (8). Based on a crystallographic model, the receptor-binding site of the H3 subtype includes conserved residues Tyr98, His193, Glu190, Trp53,
and Leu194 (8). Two other conserved residues at positions 226 and 228 within the binding pocket determine host range specificity (3). Leu226 and
Ser228 selectively bind to α2,6 sialosides found on human and swine cells, while Gln226 and Gly228 bind to the α2,3 sialosides found predominantly
on avian cells (3,9,10).
Influenza viruses currently circulating in North American swine are subtypes H1N1, H3N2, and H1N2 (11). The classical H1N1 viruses have been
circulating in the swine population since the Spanish flu pandemic of 1918 (1). The first SIV, A/SW/IA/15/30, was isolated in 1930 and is
antigenically similar to the 1918 human influenza virus (12). From 1930 to 1998, classic H1N1 viruses were the predominantly isolated subtype from US
swine. In 1998, a new SIV subtype H3N2 emerged and became established in the North American swine population (13,14). Genetic analysis showed that it
was a triple reassortant virus containing genes from swine, human, and avian influenza viruses. The H3N2 SIV acquired the polymerase basic (PB)
protein 1, HA, and neuraminidase (NA) genes from a recent human virus, the PB2 and polymerase acidic (PA) protein genes from avian viruses, and the
nucleocapsid protein (NP), matrix (M), and nonstructural (NS) genes from the classic H1N1 swine virus (13–16). A year later, reassortment between
the H3N2 and classic H1N1 SIV resulted in a new subtype H1N2, where the HA of the H3N2 subtype was replaced by the HA from the classic H1N1 virus
(17). This H1N2 subtype caused respiratory disease in swine and continues to circulate in swine populations (18). Recently, wholly avian influenza
viruses, subtypes H4N6 (5), H3N3, and H1N1 (19), from water fowl were isolated from diseased swine in Canada; however, no evidence shows that these
viruses can be successfully maintained in swine populations. We identified and characterized a new SIV subtype H3N1 that may have arisen from
reassortment of an H3N2 turkey isolate, a human H1N1 isolate, and currently circulating swine influenza viruses."