[Phage lysis typing and epidemiology of diphtheria 1975-1984].
Phage typing of the available diphtheria strains from epidemics and isolated diphtheria infections in the Federal Republic of Germany since 1975 showed that the various waves of the disease were caused by pathogenic strains which differed from each other in lysis type and lysogenetic spectrum. The individual regional outbreaks, therefore, were not epidemiologically interlinked. Both a high incidence of diphtheria cases and isolated cases occurring in a particular region and within the same time period, however, were caused by the same pathogen with identical lysis type and lysogenetic pattern. On the other hand, the toxinogenic strains introduced from countries with a high prevalence of the disease had clearly different typing characteristics. According to our present studies on the incidence of pathogen carriers, no toxin-producing diphtheria bacteria are circulating in the indigenous population. It can be assumed, therefore, that the outbreaks of diphtheria during the last few years were caused by such imported strains. Since the importation of toxin-producing diphtheria bacteria is unavoidable and may occur at all times, universal active immunisation in childhood, as well as timely revaccination of adolescents and adults, are mandatory prophylactic measures to prevent new epidemics.