[Diphtheria epidemic occurring on the North Shore of the St. Lawrence River in the fall of 1974].

An outbreak of diphtheria occurred on the North Shore of the St. Lawrence River at the beginning of September 1974. It started with the death of an 18-year-old forest worker Sept. 5, spread over a vast area of the North Shore and lasted until the end of October that year. Eleven strains of toxigenic Corynebacterium diphtheriae intermedium, type K were isolated. Eleven of the 12 patients had characteristic diphtheritic pharyngitis with pseudomembranes. Preventive measures, set forth immediately after the third case was declared, included the following: (a) daily surveillance of all contacts, (b) isolation or preventive hospitalization of persons with all types of pharyngitis, (c) mass vaccination of all susceptible persons and (d) search for healthy carriers of the germ. No strains of toxigenic C. diptheriae were isolated from patients preventively hospitalized or from the 1235 individuals among whom carriers were sought. Among the main characteristics of this epidemic, the mean age of the patients (17 years), their mobility and their habits are factors that could have made it almost uncontrollable. It is also remarkable that this outbreak occurred in such a scattered population of adolescents, in 82% of whom the Schick test was negative.