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.
Ghedin
Elodie
E
Center for Vaccine Research, Department of Computational Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
Wentworth
David E
DE
Halpin
Rebecca A
RA
Lin
Xudong
X
Bera
Jayati
J
DePasse
Jay
J
Fitch
Adam
A
Griesemer
Sara
S
Hine
Erin
E
Katzel
Daniel A
DA
Overton
Larry
L
Proudfoot
Kathleen
K
Sitz
Jeffrey
J
Szczypinski
Bridget
B
StGeorge
Kirsten
K
Spiro
David J
DJ
Holmes
Edward C
EC
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