The onset of active tuberculosis occurs before symptoms are apparent. Better understanding early subclinical stages will facilitate the development of novel diagnostic tests and interventions to prevent disease progression. This is particularly important in patients who are co-infected with the HIV-1 virus because they are more likely to experience the progression of tuberculosis. Researchers recently identified a unique pattern of activated immune system genes in blood samples from asymptomatic patients with HIV infection and early subclinical tuberculosis. Moreover, the activation of related immune genes was evident one year prior to tuberculosis disease presentation in HIV-uninfected people. The study, published in the Proceedings of the National Academy of Sciences, was partly funded by NHLBI.