United States-Mexican Border: TB Resistance and Challenges

The proximity of California to Mexico, where tuberculosis (TB) is endemic, has resulted in a higher incidence of the disease in the area across the border from Tijuana to San Diego than in the entire state of California. Adding to the crisis, Tijuana has had an ongoing HIV epidemic among drug-injecting abusers and female sex workers. Advancing HIV disease leads to the reactivation of latent TB infection in these groups, resulting from their compromised immune systems. The epidemic exacerbated by co-infection with TB is a leading cause of death in these individuals.

In a 2007 Centers for Disease Control and Prevention (CDC) study of 503 participants, researchers determined the prevalence of TB in high-risk populations by using the interferon-gamma release assay (IGRA), QuantiFERON^® TB Gold In-Tube (QFT) assay (Cellestis Ltd., Carnegie, Victoria, Australia) to detect M. tuberculosis infection and the Determine^® Rapid HIV Antibody Test (Abbott Laboratories, Boston, MA) to detect HIV infection. Unlike screening with the TB skin test (TST) in the U.S., populations in Mexico vaccinated with bacille Calmette-Guerin (BCG) require a more accurate whole blood assay (i.e., IGRA) performed on persons, including children >5 years, at high risk for TB disease. Skin tests performed on people vaccinated with BCG can yield false-positive reactions.^17,18