Unseasonal transmission of H3N2 influenza A virus during the swine-origin H1N1 pandemic.
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.
Center for Vaccine Research, Department of Computational Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
Elodie
E
Ghedin
David E
DE
Wentworth
Rebecca A
RA
Halpin
Xudong
X
Lin
Jayati
J
Bera
Jay
J
DePasse
Adam
A
Fitch
Sara
S
Griesemer
Erin
E
Hine
Daniel A
DA
Katzel
Larry
L
Overton
Kathleen
K
Proudfoot
Jeffrey
J
Sitz
Bridget
B
Szczypinski
Kirsten
K
StGeorge
David J
DJ
Spiro
Edward C
EC
Holmes
D000818:Animals; D004196:Disease Outbreaks; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000302:isolation & purification; D009980:Influenza A virus / Q000235:genetics / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000635:transmission* / Q000821:virology; D009518:New York / Q000453:epidemiology; D010802:Phylogeny; D012621:Seasons; D017421:Sequence Analysis; D013552:Swine