The full-genome sequence of A/swine/Henan/1/2010, a strain of influenza A virus isolated in central China, was determined. Phylogenetic analyses show that its eight genomic segments are human-like, and some of its segments have appeared in swine H1N2, swine H1N1, and human H1N2 influenza viruses.

The 'classical' swine H1N1 influenza A virus lineage was established after the devastating 1918 human pandemic virus entered domestic pig herds. A descendent of this lineage recently re-emerged in humans as the 2009 pandemic H1N1 virus. Adaptation in pigs has led to several changes in the multifunctional viral NS1 protein as compared with the parental 1918 virus, most notably a K217E substituti...

Zoonotic infections with swine influenza A viruses are reported sporadically. Triple reassortant swine influenza viruses have been isolated from pigs in the United States since 1998. We report a human case of upper respiratory illness associated with swine influenza A (H1N1) triple reassortant virus infection that occurred during 2005 following exposure to freshly killed pigs.

In late summer through early winter of 1998, there were several outbreaks of respiratory disease in the swine herds of North Carolina, Texas, Minnesota, and Iowa. Four viral isolates from outbreaks in different states were analyzed genetically. Genotyping and phylogenetic analyses demonstrated that the four swine viruses had emerged through two different pathways. The North Carolina isolate is ...

Adaptive mutations that have contributed to the emergence of influenza A pandemic (H1N1) 2009 virus, which can replicate and transmit among humans, remain unknown. We conducted a large-scale scanning of influenza protein sequences and identified amino acid-conserving positions that are specific to host species, called signatures. Of 47 signatures that separate avian viruses from human viruses b...

The general population is concerned about the probable devastating effects of pandemic H1N1 2009. Based upon the 1918 Spanish flu pandemic, scientific publications and theories, the idea that swine flu parties may achieve passive immunity against pandemic H1N1 2009 has been proposed. Public health officials have asked the general public not to resort to these parties. However, no concrete evide...

In April 2009, pandemic H1N1/09 influenza, which originated from swine influenza, appeared in North America, and it has since spread globally among humans. It is important to know how swine influenza A virus broke the host barrier to cause a pandemic. We analyzed 673 strains of human, avian, and swine influenza viruses and assessed the internal genes PB2, PB1, PA, NP, M, and NS. Here we found a...

The 2009 swine-origin H1N1 influenza, though antigenically novel to the population at the time, was antigenically similar to the 1918 H1N1 pandemic influenza, and consequently was considered to be "archived" in the swine species before reemerging in humans. Given that the H3N2 is another subtype that currently circulates in the human population and is high on WHO pandemic preparedness list, we ...

Swine origin influenza was first recognized in the border area of Mexico and United States in April 2009 and during a short span of two months became the first pandemic. The currently circulating strain of swine origin influenza virus of the H1N1 strain has undergone triple reassortment and contains genes from the avian, swine and human viruses. It is transmitted by droplets or fomites. Incubat...

Hemagglutinin (HA) of influenza viruses is a cylindrically shaped homotrimer, where each monomer comprises two disulfide-linked subdomains HA1 and HA2. Influenza infection is initiated by binding of HA1 to its host cell receptors and followed by the fusion between viral and host endosomal membranes mediated by HA2. Human influenza viruses preferentially bind to sialic acid that is linked to gal...