Tuberculosis is the most common opportunistic infection in AIDS patients worldwide due to the high global prevalence of Mycobacterium tuberculosis and the profound immunosuppression caused by HIV. HIV infection significantly reduces CD4+ T-cell counts, impairing the body's ability to contain latent tuberculosis infection. This leads to either reactivation of latent TB or rapid progression of new infections. In many regions, especially low and middle-income countries, tuberculosis remains the leading cause of morbidity and mortality among HIV-infected individuals, surpassing other opportunistic infections like Pneumocystis pneumonia. The dual epidemic necessitates integrated HIV and TB screening and treatment programs.

Reference: Harrison's Principles of Internal Medicine, Kasper et al., 20th Edition.