Tuberculosis: TB

About tuberculosis: TB

Tuberculosis (TB) is an infectious disease that usually affects the lungs but can affect any part of the body. 

It is a serious illness caused by active TB germs.

After the TB germs enters the body, in most cases, body defences control the germs by building a wall around them, the way a scab forms over a cut. 

The germs can stay alive inside these walls for years in an inactive or latent state.

This is known as latent TB infection.

While TB germs are active, they cannot harm the person and they cannot spread to other people.

The person is infected but not sick and is unlikely to be aware that he or she is infected.

The only way to tell whether the germs are there is by having a Mantoux test which is a skin test, or a special blood test.

Inactive TB germs cannot hurt you, but if body defences are weakened for any reason, the wall around the TB germs can become weakened and the germs can become active and multiply to progress to disease and make the person sick.

This may be years later due to:

  • ageing
  • a serious illness
  • developing diabetes
  • drug or alcohol abuse
  • HIV infection
  • treatments such as chemotherapy for cancer
  • steroid medication or other medications for medical conditions that alter the immune system such as for severe arthritis.

Signs and symptoms

TB can affect any part of the body but the lungs are the most common target.

People with TB disease may have some or all of the following symptoms:

  • persisent cough for more than two weeks
  • fevers
  • weight loss
  • night sweats.

How it's spread

TB is spread when people who have active untreated TB germs in their lungs or throat cough, sneeze or speak and send their germs into the air.

Other people who breathe these germs into their lungs can become infected.

People who breathe in TB germs usually have had close contact with someone who has the disease.

TB is not spread by handling objects that the patient has come in contact with such as dishes, drinking glasses, sheets or clothing.

Print all pages in this section

Last updated: 27 June 2017