[Ubiquitousness of viruses and the presumption of their innocuousness (the facts and the concept)].

A concept is presented based on the currently available data according to which viruses are a necessary element of nature playing a certain role in the adaptation of organisms to the conditions of existence. The pathology caused by a virus infection, exquisite for the great majority of viruses, is for a number of them a consequence of individual defectness of the immune system of the host, the pathology of the adaptation process. The latter presumes a shift of the therapeutic approach to the primary effect on the immune systems of the host.