EN
Influenza viruses of group A, being the etiological agent of the seasonal human influenza, as well as those causing disease in birds and also viruses of swine influenza, were characterized. The present situation world wide was presented. The avian influenza lasting since 2003, caused by H5N1, was identified in 62 countries, causing all together death or culling of 220 milions of birds. The disease is classified as an avian and not a human influenza. The virus infects humans with low frequency, the transmission from human to human is not occurring or is occurring sporadically, however the mortality is 60 per cent of the diseased persons. The influenza, which is noted at present, is a disease of humans and the causing virus H1N1 is a quadruple genetic combination of avian, human and swine virus genomic segments. Until now the coarse of the disease is mild. However the number of confirmed human cases and mortality is increasing. The disease has been diagnosed in 33 countries (data from the 14th of May 2009) and WHO has declared the fifth phase of pandemic alert. Because of a high possibility of mutation and reasortation with avian and swine viruses continuous monitoring of influenza viruses in the animal reservoir is necessary which requires steady medical and veterinary cooperation.