Influenza virus infections have been associated with increased morbidity and they play an important role in the excess mortality reported every winter season in the northern hemisphere; this deleterious effect is more pronounced among elderly population [1,2]. Annually, it was estimated that 291,000 to 645,000 influenza-related deaths occur worldwide [2]. Apart from mortality, influenza infections cause an important burden on healthcare systems worldwide with an important number of medical visits and hospitalizations.
