ABSTRACT
The initial wave of swine-origin influenza A virus (pandemic H1N1/09) in the United States during the spring and summer of 2009 also resulted in an increased vigilance and sampling of seasonal influenza viruses (H1N1 and H3N2), even though they are normally characterized by very low incidence outside of the winter months. To explore the nature of virus evolution during this influenza "off-season," we conducted a phylogenetic analysis of H1N1 and H3N2 sequences sampled during April to June 2009 in New York State. Our analysis revealed that multiple lineages of both viruses were introduced and cocirculated during this time, as is typical of influenza virus during the winter. Strikingly, however, we also found strong evidence for the presence of a large transmission chain of H3N2 viruses centered on the south-east of New York State and which continued until at least 1 June 2009. These results suggest that the unseasonal transmission of influenza A viruses may be more widespread than is usually supposed.
Subject(s)
Disease Outbreaks , Influenza A Virus, H1N1 Subtype , Influenza A Virus, H3N2 Subtype , Influenza, Human/transmission , Animals , Humans , Influenza A Virus, H1N1 Subtype/genetics , Influenza A Virus, H1N1 Subtype/isolation & purification , Influenza A Virus, H3N2 Subtype/genetics , Influenza A Virus, H3N2 Subtype/isolation & purification , Influenza A virus/genetics , Influenza A virus/isolation & purification , Influenza, Human/epidemiology , Influenza, Human/virology , New York/epidemiology , Phylogeny , Seasons , Sequence Analysis , SwineABSTRACT
We report here the first complete sequences of two Keystone virus (KEYV) genomes isolated from Florida in 2005, which include the first two publicly available complete large (L) gene sequences. The sequences of the KEYV L segments show 75.99 to 83.86% nucleotide similarity with those of other viruses in the California (CAL) serogroup of bunyaviruses.