Human Infection with a Triple‐Reassortant Swine Influenza A(H1N1) Virus Containing the Hemagglutinin and Neuraminidase Genes of Seasonal Influenza Virus

Abstract

A reassortant influenza A(H1N1) virus of swine origin distinct from the pandemic H1N1 2009 strain was isolated from 3 patients, all of whom worked at the same large hog operation in Saskatchewan, Canada. The genomic composition of the isolates has not been previously reported, to our knowledge, and was the product of a genetic reassortment between seasonal H1N1 and triple-reassortant influenza virus that emerged in North American swine during the late 1990s. The neuraminidase and hemagglutinin genes of A/Saskatchewan/5350/2009, A/Saskatchewan/5351/2009, and A/Saskatchewan/5131/2009 were derived from human H1N1 virus and were closely related to those of A/Brisbane/59/2007.

Characterization of H1N1 Swine Influenza Viruses Circulating in Canadian Pigs in 2009

“…In contrast, the 2004 humanlike swine isolates from Ontario contained cSIV internal genes instead of the TRIG cassette, with the exception of PB1, which was of human influenza A origin. The shSIV H1N1 viruses described here were highly similar to A/SK/5351/2009 and, based on the fact that isolation from humans preceded the isolation from pigs by a month, it is likely that this virus was transmitted from humans to pigs (1). Continued surveillance will be required to know whether this most recent shSIV, representing the ␦3 HA phylogenetic cluster, will cocirculate with conSIV.…”

“…This example highlights the possibility of shSIV and human seasonal H1 viruses recycling between pigs and humans. Because the HA and NA are of seasonal human influenza A origin, the human population is likely to have immunity to these viruses as indicated by the mild disease in the case reported by Bastien et al (1). However, human seasonal H1N1 appears to have been replaced by pH1N1, and immunity to the former in the human population may wane over the coming years, whereas shSIV could continue to evolve in the swine population.…”

“…Although these viruses were thought to have spread widely in Ontario pigs, it is not known whether they persisted within the Canadian swine population. Following the emergence of the triple-reassortant H3N2 in the late 1990s, influenza A viruses bearing human-like HA and NA with a TRIG backbone have been isolated from humans and swine in the United States and Canada (1,24). These viruses resulted from reassortments between seasonal human H1N1 and swine TRIG-containing viruses, which was the case with the human-like H1N1 viruses described in this report.…”

Dendritic Cell Activation by Recombinant Hemagglutinin Proteins of H1N1 and H5N1 Influenza A Viruses

“…In 2009, a swine-origin H1N1 strain emerged from the genetic reassortants of existing human, avian, and swine influenza viruses, resulting in a global pandemic marked by symptoms more severe than those associated with seasonal influenza virus (3,24). According to comparative pathology in macaque monkeys, H5N1 induces greater cytokinemia, tissue damage, and interference with immune regulatory mechanisms than H1N1 infection (2).…”

PhyloFlu, a DNA Microarray for Determining the Phylogenetic Origin of Influenza A Virus Gene Segments and the Genomic Fingerprint of Viral Strains

“…One of them (isolate A/Iowa/CEID23/05) shared its genotype with triple reassortant (H1N1) viruses that emerged in U.S. swine in the late 1990s following the emergence of related human/swine/avian triple reassortant H3N2 and H1N2 subtypes in American pigs (19). The other three reassortant viruses identified by the microarray were the product of a genetic reassortment between human seasonal H1N1 and swine triple reassortant virus strains; the HA and NA genes of strains A/Saskatchewan/5350/2009, A/Saskatchewan/5351/2009, and A/Saskatchewan/5131/2009 were derived from the human H1N1 virus, while the other six genes came from the triple reassortant strain (20).…”