The Infectious Diseases Epidemiology Unit currently studies human immunodeficiency virus (HIV) and tuberculosis (TB). Specific aims of our HIV studies are to determine and investigate: 1) the incidence, risk factors, clinical, and immunologic associates of HIV transmission; 2) events surrounding primary HIV infection; 3) the prevalence, incidence, and interactive effects of Mycobacterium tuberculosis and viral pathogens; 4) the design and implementation of clinical trials of HIV vaccines; and 5) factors associated with natural resistance to HIV infection.