Abstract

H3N2: Despite the late-season 3c3.a epidemic in the USA, we predict clade 3c2.a viruses will continue to predominate in the H3N2 population. Within clade 3c2.a, the 171K variant has spread rapidly so that the majority of recent H3N2 infections are comprised of 171K viruses. Barring the emergence of a new antigenic variant, we believe 171K will continue to predominate.

H1N1pdm: The clade 6b.1, comprising 84N/162N/216T, has continued to rise and predominate in the H1N1pdm population throughout 2016. Almost all circulating H1N1pdm viruses are now 6b.1. There is not yet obvious evolution within this clade.

B/Vic: Within clade 1A viruses, the clade 129D/146I/117V has risen to high frequency, but at a rate that suggests a smaller effect of natural selection. At this point, 117V viruses are dominant in the global viral population.

B/Yam: Clade 3 has continued to predominate the B/Yamagata population. Within clade 3 the 172Q/251V subclade has risen to predominate. There is limited diversity within 172Q/251V viruses, with the largest subclade comprised of 211R viruses.