Genetic diversity of influenza B virus in 2009-2010 and 2010-2011 in Tunisia

Objective: The authors had for aim to characterize influenzaB strains having circulated in Tunisia to identify new mutations and compare them with reference strains. Methods: The epidemiological surveillance of influenza allowed identifying 19patients with symptoms related to respiratory infection, who had been infected by influenza B strains isolated in several regions of Tunisia in 2009-2010 and in 2010-2011. Laboratory identification and detection of mutations in the segment encoding hemagglutinin of influenza viruses was performed by real time PCR and sequencing. Results: The two influenzaB Tunisian strains of the 2009-2010 season belonged to the Victoria lineage, whereas 2010-2011 season strains belonged to B/Victoria/2/87 and B/Yamagata/16/88 lineages with a dominance of the Yamagata lineage (76%). This study allowed identifying amino acid substitutions: T121A, S150I, N165Y, T181A, G183R, D196N, S229D, M251V and K253R in the B/Yamagata lineage; L58P, N75K, K109N, N165K, S172P and K257R into the B/Victoria lineage. These mutations were specific of Tunisian groups of variants. Most influenza B-Yamagata lineage viruses (69%) were associated with severe cases. Conclusion: Molecular analysis of the various influenzaB strains circulating in Tunisia is useful to detect new mutations that can modify the phenotype of influenza strains.