The abstract for a study explaining the trends of influenza viruses in swine herds. The emergence of H3N2 in the 1990s resulted in new recombinants, and pH1N1 in 2009 brought interest to studying flu strains in livestock. Strains found in swine herds include H1N1 with 2 additional genes and TRIG cassette, pH1N1, recombinants of human H1N1 and rH3N2, and recombinants of H3N2. The US has reported 7 strains in swine herds. Influenza is becoming a more complex virus, and it is possible multiple strains will continue to circulate or that one will emerge as dominant.