During the last two influenza seasons, one of the predominant influenza A types (H1N1) has developed complete resistance to oseltamivir, the primary treatment option. The virus does, however, remain sensitive to zanamavir and amantadine. There is no unequivocal explanation for this slide in the development of resistance. The best prevention strategy remains vaccination of the general population to avoid immunity. Future antiviral treatment calls for knowledge about resistance to existing types of influenza and the availability of all three types of antiviral medication.