The current therapeutic regimen for influenza A viruses is limited to two classes of drugs: the adamantanes (amantadine and rimantadine) and the neuraminidase inhibitors (oseltamivir and zanamivir). However, the natural and/or acquired resistance to these drugs has been reported [9, 10] . Resistance to adamantanes is prevalent among seasonal and avian influenza A viruses significantly reducing their usefulness [11, 12] . The sudden and widespread emergence of resistance to oseltamivir among prepandemic H1N1 viruses has raised further concerns over the current therapeutic options [13, 14] . Oseltamivir resistance was reported in patients infected with the pandemic H1N1 viruses and highly virulent H5N1 viruses [15, 16] . The resistance to zanamivir is rare [17] , but its use is limited to patients who can actively inhale it, which often excludes young children, impaired older adults or patients with underlying airway disease [14] , that is the groups of patients most vulnerable to serious influenza infection complications.