[Priorities among antitubercular measures: epidemiologic arguments]

A patient with positive smear tuberculosis infects approximately 50% of his domestic contacts; post-primary morbidity may reach 10% of the cases infected under the age of 24 years. Infection rate among professional and social contacts is low and the morbidity much lower. Smear-positive tuberculous patients develop the disease in a few months, therefore indiscriminate case finding is not effective in disclosing patients before they are infectious. Smear-negative, culture-positive patients do not play a role as far as epidemiology is concerned. Prognostic significance of tuberculin conversion depends upon the duration and closeness of the contact with the infectious patient, and chemoprophylaxis of infected contacts reduces post-primary morbidity. Chemotherapy of smear-positive patients suppresses infectiousness in a few weeks, where it lasted for several months previously. Therefore hospitalization of treated patients does not afford additional protection to contacts, and disinfection is superfluous. In a country where tuberculosis prevalence is low, the influence of BCG vaccination in decreasing morbidity can hardly be demonstrated. The three main antituberculous measures remain case-finding of smear-positive patients, identification of infected domestic contacts, and their treatment.