title: 2009 Swine-origin influenza A (H1N1) resembles previous influenza isolates.
abstract: BACKGROUND
  In April 2009, novel swine-origin influenza viruses (S-OIV) were identified in patients from Mexico and the United States. The viruses were genetically characterized as a novel influenza A (H1N1) strain originating in swine, and within a very short time the S-OIV strain spread across the globe via human-to-human contact.
  
  
  METHODS
  We conducted a comprehensive computational search of all available sequences of the surface proteins of H1N1 swine influenza isolates and found that a similar strain to S-OIV appeared in Thailand in 2000. The earlier isolates caused infections in pigs but only one sequenced human case, A/Thailand/271/2005 (H1N1).
  
  
  CONCLUSIONS
  Differences between the Thai cases and S-OIV may help shed light on the ability of the current outbreak strain to spread rapidly among humans.
authors.affiliation: Center for Bioinformatics and Computational Biology, Institute for Advance Computer Studies, University of Maryland, College Park, Maryland, United States of America. carlk@umiacs.umd.edu
authors.forename: Carl
authors.initials: C
authors.lastname: Kingsford
authors.forename: Niranjan
authors.initials: N
authors.lastname: Nagarajan
authors.forename: Steven L
authors.initials: SL
authors.lastname: Salzberg
mesh_terms: D036022:Capsid Proteins / Q000235:genetics; D005814:Genes, Viral; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification* / Q000235:genetics; D016865:Reassortant Viruses / Q000145:classification / Q000235:genetics; D013045:Species Specificity
chemical_list: D036022:Capsid Proteins