Swine Influenza Virus A (H3N2) Infection in Human, Kansas, USA, 2009

Seroprevalence of a Novel Influenza A (H3N2) Variant Virus in the Japanese Population

“…Since 1998, H3N2 triple-reassortant viruses have been circulating among North American pigs and carry the PB2 and PA genes of North American avian virus origin; hemagglutinin (HA), neuraminidase (NA), and PB1 genes of human H3N2 virus origin; and the NP, M, and NS genes of classical swine virus origin (4). The first documented case of human infection with a triple-reassortant H3N2 virus occurred in Canada in 2005 (4), and seven additional cases were documented in the United States (U.S.) during the period 2009-2010 (5,6). Such viruses are designated H3N2-variant (H3N2v) viruses when found in humans.…”

Pathogenesis and transmission of swine origin A(H3N2)v influenza viruses in ferrets

“…In particular, TRS H3N2 viruses with a human lineage polymerase subunit polymerase basic 1 (PB1) gene, avian lineage PB2 and polymerase acidic (PA) genes, and swine lineage nucleoprotein (NP), matrix (M), and nonstructural (NS) genes, referred to as the triple-reassortant internal gene (TRIG) constellation, have been isolated widely in pigs throughout the United States (6)(7)(8)13). From the late 1990s to 2009, these novel variants of H3N2 viruses [A(H3N2)v] were limited to transmission among swine, with only occasional detections of transmission to humans (14). However, between September and November 2010, five cases of human infection with the novel swine-origin A(H3N2)v were reported (15).…”

“…These findings suggest that swine-origin H3N2 viruses have the potential to cause additional human disease. A/Kansas/13/2009 (KS/09) was isolated from a 12-y-old male who presented with fever, cough, and sore throat after contact with healthy-appearing swine while attending a county fair (14). A/Minnesota/11/10 (MN/10) virus was isolated from a 37-y-old Author contributions: M.B.P., C.P., H.Z., T.R.M., R.R., N.J.C., R.S., J.M.K., and T.M.T.…”

Emergence of novel reassortant H3N2 swine influenza viruses with the 2009 pandemic H1N1 genes in the United States

“…A Kansas boy who was in contact with healthy pigs while attending a county fair in 2009 was reported to have been infected with a triple reassortant H3N2 SIV. This H3N2 virus does not seem to be transmitted efficiently among humans because his three household contacts did not show signs of illness [4]. Recently, two younger children from Indiana and Pennsyl-vania were infected by reassortant H3N2 SIVs that contained only the M gene from pH1N1 [3].…”