Basic TB Facts

Tuberculosis (TB) disease is an infectious disease caused by a bacterium called Mycobacterium tuberculosis.  The bacteria usually attack the lungs, but TB bacteria can infect any part of the body including the kidney, spine, and brain.  If not treated properly, TB disease can be fatal.  TB is almost always curable with antibiotics that are available in countries such as the United States.

The Difference between Latent TB Infection and TB Disease

Not everyone infected with TB bacteria becomes sick.  As a result, two TB-related conditions exist:  latent TB infection and active TB disease.
Latent TB Infection 

Latent TB infection (LTBI) means the TB bacteria are sleeping or dormant in the body.  For most people who breathe in TB bacteria and become infected, the body is able to fight the bacteria to stop them from growing and the bacteria become dormant.

People with latent TB infection do not feel sick and do not have any symptoms.  The only sign of TB infection is a positive reaction to the tuberculin skin test or special TB blood test.  People with LTBI are not infectious and cannot spread TB bacteria to others.  However, if the TB bacteria become active in the body and start multiplying, the person will get sick with TB disease. 

Persons with LTBI are often advised to take antibiotics for several months in order to kill the sleeping bacteria and to prevent the development of active TB disease.

TB Disease

TB disease means the TB bacteria are active and the immune system can’t stop them from growing.  TB disease will make you sick.  People with TB disease may spread the bacteria to people they spend time with every day.

Ten percent of people in the U.S. with untreated LTBI will develop TB disease.  Some people develop TB disease soon after becoming infected (within weeks) before their immune system can fight the TB bacteria.  Others may get sick years later, when their immune system becomes weak for another reason.  For persons whose immune systems are weak, especially those with diabetes or HIV infection, the risk of developing TB disease is much higher than for persons with normal immune systems. 

Persons with active TB disease are treated with several antibiotics for at least 6-12 months.  It is vital that these medications be taken regularly and treatment completed.  Lengthy treatment is necessary as it is difficult to eradicate TB bacteria from the body.

The Difference between Latent TB Infection and TB Disease
A Person with Latent TB Infection   Person with TB Disease

Has No Symptoms

Symptoms usually come on slowly
over a period of weeks. Symptoms may include:

  • A bad cough that lasts 3 weeks or longer
  • Pain in the chest
  • Coughing up blood or sputum
  • Weakness or fatigue
  • Weight loss
  • No appetite
  • Chills
  • Fever
  • Drenching night sweats

Does not feel sick

Usually feels sick
Cannot spread TB bacteria to others May spread TB bacteria to others
Usually has a skin or blood test result
indicating TB infection
Usually has a skin or blood test result
indicating TB infection
Has a normal chest x-ray and a
negative sputum smear
May have an abnormal chest x-ray or
positive sputum smear or culture 
Usually advised to take treatment
for latent TB infection to prevent
active TB disease
Needs treatment to treat active TB disease 
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