[Infectious diseases yesterday and today].

The authors present examples demonstrating that in the last decades we witnessed the discovery of new nosological units and their infectious agents, the detection of the infectious origin of "old" diseases the aetiology of which was still recently obscure, infectious attacks of people by diseases which were considered animal infectious only, as well as the more frequent incidence of opportune infections due to impairment of the immune state of the human organism. These changes have many reasons such as the development of properties of microorganisms, lifestyle changes of the human population, advances in medicine, and last but not least improving microbiological diagnosis. Attention is drawn to the fact that even in a time when so-called diseases of civilization are in the foreground of interest our awareness of infectious diseases must not slacken. Only all-round international surveillance can prove successful.