Abstract

Planning of effective responses to the recent resurgence of tuberculosis in the United States, and particularly in New York City, requires review of our knowledge of the factors that led to the decline of tuberculosis in the U.S. and other countries during the nineteenth and the first three-quarters of the twentieth century, and the recent changes in these same factors and the rise of new factors that have contributed to its resurgence. Because the analysis of the impact of all of these factors in both the remote and the recent past is controversial, it is important to use a well-defined framework to organize the analysis. The framework we will use is shown in Table 1. To the classic epidemiologic triad of Agent, Host and Environment it adds the category of Health Services. In this paper we redefine both the classic and new categories using current disciplines and concepts applicable to tuberculosis.