The body can harbor the bacteria that cause tuberculosis and the immune system can normally prevent you from getting sick. This is the reason that doctors will make the distinction between latent and active tuberculosis. Latent TB (tuberculosis) is when you have an infection but have no symptoms. Latent TB is not contagious but can become active. Even with latent TB, treatment is important. Active TB makes you sick and is contagious and can easily spread to others. TB can become active weeks or years after you have become infected.