Molecular characterization of influenza b circulating in casablanca-morocco during 2010-2013

Influenza B is often regarded as the milder form of the disease. The aim of this study was to characterize the genetic diversity of the influenza B viruses identified in Casablanca during 2010-2013 among patients with influenza-like illness.  
Materials and Method
Samples were collected from patients with influenza-like illnesses (ILI) and screened for influenza viruses by One-Step Real-Time RT-PCR, and Influenza B viruses identified were subsequently sequenced and analyzed phylogenetically.
Findings
Of the 760 nasopharyngeal swabs collected during 2010-2013,  a total of 226 (30%) influenza viruses were identified by real time RT-PCR, 173 (23%) were influenza A and 53(7%) were influenza B. Molecular Characterization of the HA1 Gene of Influenza B identified  during 2010-2011 showed that they belong to B/Victoria lineage and were closely related to the vaccine virus B/Brisbane/60/2008.
Influenza B activity remained very low during 2011-2012. In 2012-2013, a co-circulation of both lineages, Victoria and Yamagata, was detected. Most of the strains that belonged to the Victoria lineage were closely related to the B/Brisbane/60/2008 vaccine strain and influenza B identified belonging to Yamagata lineage were related to the vaccine virus  B/Wisconsin/1/10.
Conclusion
The study confirmed the co-circulation of Victoria and Yamagata lineages of influenza B viruses. Therefore, surveillance and monitoring of genetic variations among circulating influenza B viruses is important for selection of annual vaccine strains as quadrivalent flu vaccine including influenza A (H1pdm09 and H3) and both lineages of influenza B.