title: Reassortment and evolution of current human influenza A and B viruses.
abstract: During the 2001-2002 influenza season, human influenza A (H1N2) reassortant viruses were detected globally. The hemagglutinin (HA) of these H1N2 viruses was similar to that of the A/New Caledonia/20/99 (H1N1) vaccine strain both antigenically and genetically, while their neuraminidase (NA) was antigenically and genetically related to that of recent human influenza H3N2 reference viruses such as A/Moscow/10/99. All six internal genes of the H1N2 reassortants originated from an H3N2 virus. After being detected only in eastern Asia during the past 10 years, Influenza B/Victoria/2/87 lineage viruses reappeared in many countries outside of Asia in 2001. Additionally, reassortant influenza B viruses possessing an HA similar to that of B/Shandong/7/97, a recent B/Victoria/2/87 lineage reference strain, and an NA closely related to that of B/Sichuan/379/99, a recent B/Yamagata/16/88 lineage reference strain, were isolated globally and became the predominant influenza B epidemic strain. The current influenza vaccine is expected to provide good protection against H1N2 viruses because it contains A/New Caledonia/20/99 (H1N1) and A/Panama/2007/99 (H3N2) like viruses whose H1 HA or N2 NA are antigenically similar to those of recent circulating H1N2 viruses. On the other hand, widespread circulation of influenza B Victoria lineage viruses required inclusion of a strain from this lineage in influenza vaccines for the 2002-2003 season.
authors.affiliation: Influenza Branch, Centers for Disease Control and Prevention, Mail Stop G16, 1600 Clifton Road, NE, Atlanta, GA 30333, USA. xxu@cdc.gov
authors.forename: Xiyan
authors.initials: X
authors.lastname: Xu
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Lindstrom
authors.forename: Michael W
authors.initials: MW
authors.lastname: Shaw
authors.forename: Catherine B
authors.initials: CB
authors.lastname: Smith
authors.forename: Henrietta E
authors.initials: HE
authors.lastname: Hall
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Mungall
authors.forename: Kanta
authors.initials: K
authors.lastname: Subbarao
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Cox
authors.forename: Alexander
authors.initials: A
authors.lastname: Klimov
mesh_terms: D019143:Evolution, Molecular; D014943:Global Health; D006385:Hemagglutination Inhibition Tests; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D009980:Influenza A virus / Q000145:classification / Q000235:genetics*; D009981:Influenza B virus / Q000145:classification / Q000235:genetics*; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology; D009439:Neuraminidase / Q000235:genetics; D010802:Phylogeny; D011159:Population Surveillance; D016865:Reassortant Viruses / Q000235:genetics*; D011995:Recombination, Genetic
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D009439:Neuraminidase