During the nineteenth century, overcrowding and poor sanitation were thought to create miasmas, capable of spreading disease through the air. Infection control at that time focused on poverty reduction, control of the miasma. Although TB was then widely believed to be a hereditary disorder, the improvement in living conditions that took place in the nineteenth century was probably causally related to the coincident decline in the eincidence of TB. Without effective therapy, TB control remained entirely preventive, even after Koch's isolation of the tubercle bacillus in 1882 and the realization that TB is indeed infectious. Although the TB control measures then employed (sanitoria) were primitive, this conception of TB as a disease occurring as much between persons as within them was essentially correct.

Although we now confront the person with active TB with an armamentarium of powerful diagnostic and therapeutic tools, recent outbreaks of TB have made it painfully clear that these are no substitute for the elementary TB control methods, which have been impeded by technological hubris. Partially because of the altered presentation and accelerated course of TB in those with HIV infection, physicians have relearned that “atypical” radiographic patterns are actually common, even in immunocompetent hosts, that conventional culture and sensitivity techniques are disturbingly slow, and that up to 50% of persons with pulmonary TB may have negative sputum smears. Although the rate of MDRTB in most areas has remained low, physicians now recognize the fact that many patients require incentives (sometimes legislative)⁸⁰ to complete a curative course of therapy. The current focus of TB control has shifted back to the miasma, not only in the form of concern over droplet nuclei and particulate respirators⁸¹ but also in the old pseudoepidemiologic nineteenth century sense. Although TB rates are again falling, years of unchecked TB transmission have left certain populations with very high rates of TB infection and disease. The ACET recommends that screening focus on these and other highrisk groups⁸² (Table 3).

Despite all of the institutional failures of TB control outlined in this section, and despite the HIV epidemic itself, a major reduction in TB morbidity would likely occur if physicians followed current ACET guidelines for tuberculin skin testing and chemoprophylaxis. In a study of cases of active TB reported to the Oregon Health Division during 1991 and 1992, 43% of the patients had not received tuberculin skin testing as indicated and 8% had not received chemoprophylaxis as indicated⁸³. In another study conducted at three sites around the United States, few patients received tuberculin testing as indicated⁸⁴. A significant population of patients in these studies had not seen a physician before their development of active TB. Althoug TB rates are decreasing again, the elimination of the disease will require both close adherence to TB control standards and guidelines by health professionals and improved access to health care for under-served populations.