What is the difference between TB infection and Active TB disease?
When a person breathes the TB germ into their lungs, the body’s defences (antibodies) usually destroy the TB germs or wall off the germs so no damage is done. People may not even know they have been infected. A skin test is able to detect TB anti-bodies. It shows whether someone has been exposed to the TB germ. People who have had sufficient contact with the TB germ will have a positive skin test 2-12 weeks after initial exposure. This is known as TB infection. TB infection is not contagious. At the time of TB infection only about 5 per cent of people become sick with active tuberculosis disease (where the germ is doing damage). These are usually children or people who are not healthy. Others may develop active disease later in life when the TB germs that were walled off start to grow again and cause damage in the body. This happens in approximately 10 per cent of those with a positive skin test. The elderly, the immunocompromised or those with poor general health are at highest risk,
