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.