BACKGROUND An avian-like H1N1 swine influenza virus (SIV) is enzootic in swine populations of Western Europe. The virus is antigenically distinct from H1N1 SIVs in North America that have a classical swine virus-lineage H1 hemagglutinin, as does the pandemic (H1N1) 2009 virus. However, the significance of this antigenic difference for cross-protection among pigs remains unknown. OBJECTIVES We...

levels of illness but low death rates in pigs. These viruses may circulate among pigs throughout the year, but most outbreaks occur during the autumn and winter months, similar to flu outbreaks in humans. The classical swine flu virus (an H1N1 virus) was first isolated from a pig in 1930. Like all influenza viruses, swine flu viruses change constantly. Pigs can be infected by avian influenza an...

The emergence of the pandemic 2009 H1N1 influenza A virus in humans and subsequent discovery that it was of swine influenza virus lineages raised concern over the safety of pork. Pigs experimentally infected with pandemic 2009 H1N1 influenza A virus developed respiratory disease; however, there was no evidence for systemic disease to suggest that pork from pigs infected with H1N1 influenza woul...

In 1979, a lineage of avian-like H1N1 influenza A viruses emerged in European swine populations independently from the classical swine H1N1 virus lineage that had circulated in pigs since the Spanish influenza pandemic of 1918. To determine whether these two distinct lineages of swine-adapted A/H1N1 viruses evolved from avian-like A/H1N1 ancestors in similar ways, as might be expected given the...

Swine influenza was first recognized clinically in pigs at the time of the 1918 Spanish Flu pandemic [1]. From 1918 to 1998, swine influenza was almost exclusively caused by the influenza A (H1N1) classic swine virus; this virus circulated in pigs with little genetic drift [1–3] for more than 70 years. In 1998, severe influenza-like illness (ILI) was observed in pigs in the United States. The c...

Very little is known about swine influenza in northwestern China. Here, we report the complete genomic sequences of six avian-like H1N1 swine influenza viruses (SIVs) isolated in pigs in northwestern China. Phylogenetic analyses of the sequences of eight genomic segments demonstrated that they are avian-like H1N1 SIVs.

In Manitoba, Canada, several swine herds were infected by pandemic (H1N1) 2009 virus in the summer of 2009. Results of several investigations concluded that outbreaks of infection with this virus are similar in duration to outbreaks of infections with swine influenza viruses A (H1N1) and A (H3N2).

BACKGROUND Influenza viruses can generate novel reassortants in coinfected cells. The global circulation and occasional introductions of pandemic H1N1/2009 virus in humans and in pigs, respectively, may allow this virus to reassort with other influenza viruses. These possible reassortment events might alter virulence and/or transmissibility of the new reassortants. Investigations to detect such...

To assess herd immunity to swine influenza viruses, we determined antibodies in 28 paired serum samples from participants in a prospective serologic cohort study in Hong Kong who had seroconverted to pandemic (H1N1) 2009 virus. Results indicated that infection with pandemic (H1N1) 2009 broadens cross-reactive immunity to other recent subtype H1 swine viruses.

Swine Influenza Virus (H1N1) is a known causative agent of swine flu. Transmission of Swine Influenza Virus form pig to human is not a common event and may not always cause human influenza. The 2009 outbreak by subtype H1N1 in humans is due to transfer of Swine Influenza Virus from pig to human. Thus to analyze the origin of this novel virus we compared two surface proteins (HA and NA) with inf...