Approximately one-third of the global human population is infected with M. tuberculosis (or M. bovis), with 8 million new cases of TB and 2 million deaths annually. The World Health Organization declared TB a global public health emergency in 1993, focusing on implementation of directly observed therapy (DOT) in most cases.
In the United States, a continuous decline in TB incidence rates was observed until 1985, when rates began to increase again, due to factors including illicit drug use, home-lessness, HIV infection, irregular adherence to drug therapy, and evolution and spread of drug-resistant strains. Since 1992, TB rates in the United States have declined and in 2004, with effective TB-control programs, reached the lowest in recorded history (mean 4.9 cases per 100,000 population) (2). Most of the TB cases in the United States occur in foreign-born immigrants, ethnic minorities, and medically underserved populations. Rates of MDR-TB are variable, with a global median of 1% of all active TB cases, but rates can be as high as 10% to 15% in certain areas of the world. The goal of the National TB Control Program is to achieve less than one case per 100,000 by the year 2010.
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