[Virological surveillance and molecular characteristics of influenza B viruses in Hebei Province during 2004-2008].

OBJECTIVE: To understand influenza B viruses circulating and antigenic variation and distributing in Hebei province during 2004-2008. METHODS: Viruses were isolated with Madin-Darby canine kidney (MDCK) cells. Viral RNA was extracted from isolates after serological identification and transcribed into cDNA by reverse transcript and ampified by PCR. The PCR product was purified and nucleotide sequence of HA1 gene of the influenza B viruses was analyzed. RESULTS: 131 influenza B viruses were obtained from October 2004 to March 2008. Among them, 48 strains were Victoria-lineage and 83 strains were Yamagata-lineage viruses. Yamagata-lineage viruses were detected in the 2004-2005, replaced by Victoria-lineage viruses in the 2005-2006. Both Victoria-lineage and Yamagata-lineage viruses were isolated in 2006-2007 and 2007-2008. There were several amino acids substitution in both Victoria and Yamagata lineages according to the result of sequence analysis of the hemagglutinin HA1 genes, and Yamagata lineages viruses took more frequently substitution in isolates. Influenza B viruses in 2008 were differed by 8 amino acids from virus stains, in 2005 with homology of 97.4%-98.0%. CONCLUSION: The antigenicity of Victoria-lineage virus didn't take place varidation apparently in Hebei provinece during 2004-2008, but Yamagata-lineage virus took drift and caused outbreak of influenza in the epidemic season of 2007-2008.