Latent tuberculosis (LTB), also called latent tuberculosis infection (LTBI) is when a person is infected with Mycobacterium tuberculosis, but does not have active tuberculosis. Active tuberculosis can be contagious while latent tuberculosis is not, and it is therefore not possible to get TB from someone with latent tuberculosis. The main risk is that approximately 10% of these people (5% in the first two years after infection and 0.1% per year thereafter) will go on to develop active tuberculosis. This is particularly true, and there is added risk, in particular situations such as medication that suppresses the immune system or advancing age. The identification and treatment of people with latent TB is an important part of controlling this disease. Various treatment regimens are in use for latent tuberculosis. They generally need to be taken for several months. Transmission Latent disease TB Bacteria Are Spread Only from a Person with Active TB Disease ... In people who develop active TB of the lungs, also called pulmonary TB, the TB skin test will often be positive. In addition, they will show all the signs and symptoms of TB disease, and can pass the bacteria to others. So, if a person with TB of the lungs sneezes, coughs, talks, sings, or does anything that forces the bacteria into the air, other people nearby may breathe in TB bacteria. Statistics show that approximately one-third of people exposed to pulmonary TB become infected with the bacteria, but only one in ten of these infected people develop active TB disease during their lifetimes.However, exposure to tuberculosis is very unlikely to happen when one is exposed for a few minutes in a store or in a few minutes social contact. "It usually takes prolonged exposure to someone with active TB disease for someone to become infected. After exposure, it usually takes 8 to 10 weeks before the TB test would show if someone had become infected."Depending on ventilation and other factors, these tiny droplets [from the person who has active tuberculosis] can remain suspended in the air for several hours. Should another person inhale them, he or she may become infected with TB. The probability of transmission will be related to the infectiousness of the person with TB, the environment where the exposure occurred, the duration of the exposure, and the susceptibility of the host.In fact, "it isn't easy to catch TB. You need consistent exposure to the