A Major International Health Threat

Tuberculosis is a major international health issue. Worldwide, 2 billion people are actively infected with TB, 8.8 million new cases arise each year and about 20 million people are estimated to be alive and ill with the disease. TB causes approximately 2 million deaths annually.

There is a worldwide effort to identify, control and eliminate TB, which has led to coordinated and thorough treatment of TB globally. However, TB’s ability to subside to a latent form and then recur requires repeated use of diagnostic tools, even when the initial diagnosis is negative.

TB assessment is limited primarily to screening high-risk populations or diagnosis of symptomatic individuals. Suspected TB cases are investigated by expert assessment of microbes visible after acid-fast staining of smears from respiratory secretions (sputum) on microscope slides, followed up with chest x-rays, and growth studies of cultured mycobacteria with antibiotic susceptibility testing of isolated microbes. The techniques are laborious and expert-intensive.

The potential for a new diagnostic test that can identify individuals with latent TB infections is enormous. In Tuberculosis: The Global Cost of Diagnosis 2000, the total high-risk population in the U.S. that might benefit from fast, reliable, and inexpensive TB screening is estimated at 15 million individuals. According to the World Health Organization, HIV and TB form a lethal combination. TB is a leading cause of death among people who are HIV-positive, and it accounts for about 23% of AIDS deaths worldwide. Persons infected with both HIV and TB are 30 times more likely to progress to active TB disease according to USAID.

Beginning in 2000, the World Health Organization endorsed the establishment of a Global Partnership to Stop TB and set two targets for 2005: to diagnose 70% of all people with infectious TB, and to cure 85% of those diagnosed. Since then, the Stop TB Partnership has outlined new targets for 2006-2015 in accord with the Millennium Development Goals.