Active TB is when you feel sick and latent TB is when you feel well.  Active TB is also called TB disease. It’s when the bacteria that causes TB is ‘alive’ and multiplying in your body because your immune system can’t fight it. This is more common in people with HIV. People with active TB can pass TB on.  Latent TB is also called inactive TB. It’s when your immune system has been able to fight the disease and stop it from causing illness. People with latent TB can’t pass TB on. In some people, TB stays inactive for their whole life. In others, TB may become active if their immune system weakens - for example by having HIV.