The epidemiological retreat of tuberculosis; a ten-year survey of tuberculin reactors at a children's dispensary.

The epidemiological retreat of tuberculosis in the United States during the last quarter of a century presents a public health phenomenon of considerable complexity. In most other infectious diseases the success of preventive medicine has been due chiefly to the application of two principles: elimination of sources of infection and active immunization. In tuberculosis, on the other hand, a combination of several circumstances has resulted in the spectacular decline of morbidity and mortality. The most important factors are (1) elimination of bovine tuberculosis by way of compulsory tuberculin testing of cattle, (2) improvement in the standard of living and particularly housing, (3) more accurate case-finding procedures including routine standard and microfilm x-rays, (4) tuberculin testing, (5) bacteriological conversion by chemotherapy of large numbers of formerly intractable cases, and (6) BCG vaccination of potential contacts. One of the most revealing and time-honored yardsticks by which we are able to measure the