What is TB?

TB, or tuberculosis, is a disease caused by bacteria called Mycobacterium tuberculosis. The bacteria can attack any part of your body, but they usually attack the lungs.

What are the symptoms of TB disease?

Symptoms of TB depend on where in the body the TB bacteria are growing. TB bacteria usually grow in the lungs. TB in the lungs may cause:

How is TB spread?

The bacteria are put into the air when a person with TB disease of the lungs coughs or sneezes. People nearby may breathe in these bacteria and become infected. People with TB disease are most likely to spread it to people they spend time with every day. This includes family members, friends, and coworkers.

In most people who breathe in TB bacteria and become infected, the body is able to fight the bacteria to stop them from growing. The bacteria become inactive, but they remain alive in the body and can become active later. This is called latent TB infection. People with latent TB infection:

Ninety-five percent of people who have latent TB infection never develop TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease. Other people may get sick later, when their immune system becomes weak for some reason, especially people with any of these conditions:

How do I know if I have been infected with the TB bacteria?

A TB skin test is the only way to find out if you have latent TB infection. If you have a positive reaction to the skin test, other tests will be done to see if you have TB disease. These tests usually include a chest x-ray.

If you have a negative reaction to the skin test, you may need a second skin test 10 to 12 weeks after the last time you spent time with the infectious person. This is because it can take several weeks after infection for your immune system to be able to react to the TB skin test. If your reaction to the second test is negative, it is very unlikely that you have latent TB infection.

Difference Between Latent TB Infection and TB Disease

Latent TB Infection

TB Disease

Have no symptoms: Symptoms include:
Do not feel sick
  • A bad cough that lasts longer than 2 weeks
  • Pain in the chest
  • Coughing up blood or sputum
  • Weakness or fatigue
  • Weight loss
  • No appetite
  • Chills
  • Fever
  • Sweating at night
Cannot spread TB to others
Usually have a positive skin test
Chest x-ray and sputum test normal
  May spread TB to others
Usually have a positive skin test
May have abnormal chest x-ray, and/or positive sputum smear or culture


Are people with latent TB treated?

The medicine usually used for the treatment of latent TB infection is a drug called isoniazid, or INH. INH kills the TB bacteria that may be in the body and prevents active TB from developing later in life. Treatment will keep almost everyone with latent TB from ever developing TB disease.


What's in a name?

Quite a lot, actually. Find out what the M.D.s, D.O.s, P.A.s, C.M.A.s, R.N.s, M.L.T.s and R.D.s at Marquette's Medical Clinic do to help get you — and keep you — healthy. Here's a hint: It's more than just caring for your basic health needs. Find out more.