文摘
For the present study, we obtained 49 HA1 sequences from influenza B viruses isolated in Portugal during the 1994–2003 period. Phylogenetic analysis was performed and evolutionary rates were estimated by linear regression. From 1994 to 2002, all influenza B viruses isolated in Portugal belonged to Yamagata lineage. The Yamagata-like strains from 1994 to 1996, 1996–1999 and 1999–2002 revealed a high similarity with B/Beijing/184/93, B/Yamanashi/166/98 and B/Sichuan/379/99, respectively. In Portugal, Victoria-like strains reappeared at the 2002/2003-winter season. These strains formed only one branch in the phylogenetic tree, revealing a closer relationship to B/Shangdong/7/97. Phylogenetic analysis reveals Yamagata-like isolates from different branches cocirculating during the same seasons. The insertion–deletion pattern observed in Portuguese type B viruses was similar to results previously described in literature for more recent Yamagata-like strains and Victoria-like viruses. The rate of HA evolution for nucleotides was identical to published values.
