In 1992, CDC reported that (3):
A person who becomes infected with TB bacillus remains infected for years. Usually a person with a healthy immune system does not become ill, but is usually not able to eliminate the infection without taking an antituberculosis drug. This condition is referred to as "latent tuberculosis infection." Persons with latent tuberculosis infection are asymptomatic and cannot spread TB to others. Generally, a positive TB skin test is the only evidence of infection. About 10-15 million persons in this country are infected with M. tuberculosis.
According to the American Medical Association, about 70% of infectious tuberculosis cases occur among racial and ethnic minorities, and (4):
About 10% of infected persons will develop active tuberculosis at some time in their lives; approximately 5% will develop active disease within the first two years. In the absence of treatment, case fatality is about 50% in five years ... Patients with drug susceptible strains of tuberculosis can be successfully treated with a three-drug regimen of INH [isoniazid], RIF [rifampin], and PZA [pyrazinamide] given for six months with a 95% cure rate, as previously discussed.
Difficulties have arisen in ensuring a continuing supply of antituberculosis drugs in the United States due to uncertain supplies of isoniazid and other drugs (2,5).
Recently, multiple-drug-resistant tuberculosis (MDR-TB) has become a serious concern (4,6). Multiple-drug-resistant is defined as resistance to two or more primary drugs used in this country for the treatment of tuberculosis (currently isoniazid, rifampin, pyrazinamide, streptomycin, and ethambutol). In a recent survey in New York City, 33% of tuberculosis cases had organisms resistant to at least one drug, and 19% had organisms resistant to both isoniazid (INH+) and rifampin, the two most effective drugs available for treating tuberculosis. When organisms are resistant to both INH and rifampin, the course of treatment increases from 6 months to 18-24 months, and the cure rate decreases from about 95% to 60% or less.
Against this background of increasing numbers of tuberculosis cases and increasing numbers of multiple-drug-resistant cases, CDC has reported a serious new phenomenon: outbreaks
