About 10% of latent infections progress to active disease which, if left untreated, kills about half of those affected.
see post on Latent TB
Diagnosis of active TB is based on chest X-rays, as well as microscopic examination and culture of body fluids.[
IN SHORT:
Active tb means you are contagious
A definitive diagnosis of TB is made by identifying M. tuberculosis in a clinical sample (e.g., sputum, pus, or a tissue biopsy). However, the difficult culture process for this slow-growing organism can take two to six weeks for blood or sputum culture.
Thus, treatment is often begun before cultures are confirmed.