Antigenic and Genetic Characterization of Influenza B Viruses in 2012 from Slums, Dhaka, Bangladesh.

Nasal and throat swab samples were collected from 400 subjects with influenza-like illness during June to September, 2012 from two heavily crowded slums, Rayerbazar and Hazaribagh, situated southeast of Dhaka, Bangladesh. Forty-one samples were positive for influenza B virus using quantitative RT-PCR, but no influenza A virus was detected. Antigenic characterization revealed that the influenza B viruses were of Yamagata and Victoria lineages, which was confirmed from genetic analysis of hemagglutinin (HA) and neuraminidase (NA) genes. Co-circulation of influenza B viruses of both Yamagata and Victoria lineages in the slums of Dhaka indicates that introduction of a tetravalent vaccine formulation that includes both of these influenza B virus lineages would be more effective in this population.