Tuberculosis
En Español (Spanish Version)Tuberculosis (TB) is a contagious infectious disease. It can have either active or inactive forms. Although it can affect many organ systems, it mostly affects the lungs.
TB is caused by the bacterium
Mycobacterium tuberculosis
. When a person with active TB of the lungs coughs or sneezes, people nearby may inhale the bacteria. TB is easily spread in crowded conditions, though it may take several hours of continuous exposure to transmit infection. Brief or casual contact with someone who has TB will usually not lead to infection. TB is most likely to become active when spread among people who are ill or have weakened immune systems.
Pathway to the Lungs
Mycobacterium tuberculosis
is inhaled through the mouth and nose and travels down into the lungs causing TB.
© 2011 Nucleus Medical Media, Inc.
These factors increase your chance of developing active TB:
- Weakened immune system or chronic diseases (highest risk)
- HIV
infection
- Malnutrition
- Intravenous drug use
- Alcoholism
- Leukemia
,
lymphoma
, and other
cancers
-
Poorly controlled
diabetes mellitus
- Severe kidney disease
- Corticosteroids
-
Some medicines used for treating
rheumatoid arthritis
and other diseases, including
etanercept
,
infliximab
, and
adalimumab
- Suppressed immune system caused by medicines, such as drugs to prevent rejection of a transplanted organ
-
Other risks factors include:
- Silicosis
(an occupational lung disease)
- Living in crowded, indoor conditions (eg, homeless shelters, dormitories, military barracks)
- Age (infants, young children, and elderly people)
TB causes no symptoms in most patients. In others it is fatal. The bacteria lie dormant in the lungs. Bacteria may remain there permanently without causing illness. During this time, the infected person cannot spread TB to others. The infection spreads once the bacteria are active.
If you have any of these symptoms do not assume it is due to TB. These symptoms may be caused by other conditions. Tell your doctor if you have any of these:
-
Severe
cough
that lasts more than two weeks
- Coughing up blood and sputum (mucus from deep in the lungs)
- Pain in the chest
- Weakness or fatigue
- Unexplained weight loss
- Chills
- Fever
- Night sweats
- Loss of appetite
A skin test is used to screen for TB. A small amount of tuberculin test fluid is injected into the skin of the lower part of your arm. The test is positive if after 2-3 days a raised, firm welt appears at the injection site. The welt is 10 millimeters (mm) or greater in diameter (5 mm or 15 mm under some situations).
A positive test means you were exposed to TB, even if you never became ill. People at high risk for getting TB should have a skin test regularly. Also, new blood tests are available to screen for TB. Talk to your doctor to learn more.
If you have symptoms or signs of active TB, your doctor may order the following:
- Chest x-ray
- Samples of your sputum
to be tested for the bacterium
Medicine can prevent TB from becoming active. It can also help cure active TB. It is very important that you take all medicine exactly as prescribed. Take all the medicine, even if the symptoms go away. If you do not finish your medicine, you may develop drug-resistant TB. This form is very difficult to cure.
If you have a positive skin test but no signs of active TB, you may need to take medicine to prevent active TB. The drug
isoniazid
is usually given for nine months.
Another option is taking a combination of isoniazid and
rifapentine for three months.
Your doctor may give you a combination of the following drugs:
If you have active TB, you will need to use special precautions to prevent transmission to others. This will help prevent the spread of TB. You may need to stay home or stay away from crowded public places. You will also need to cover your mouth whenever you cough. You can resume your normal activities after your doctor says that you are no longer infectious. You will need to keep taking medicine until your doctor tells you to stop. Treatment for active TB typically lasts six months or longer.
If you have a positive skin test, you might prevent active TB from developing by taking medicine. There is a
vaccine
. It is not routinely used in the United States because of the unreliable protection it provides.
Talk to your doctor to learn more.
If you have active TB, you can prevent its spread by:
- Covering your mouth and nose with tissue or a handkerchief whenever you cough.
- Avoiding contact with people until your doctor says you are no longer contagious
- Taking all medicine as prescribed for the full course of treatment
American Lung Association
National Institute of Allergy and Infectious Disease
The Canadian Lung Association
Harrison TR, Braunwald E, Fauci AS, Kasper DL, Hauser SL, Longo DL, et al.
Harrison's Guide to Internal Medicine
. 16th ed. New York, NY: McGraw Hill; 2001.
Hawkridge T, Mahomed H. Prospects for a new, safer and more effective TB vaccine.
Paediatr Respir Rev
. 2011 Mar;12(1):46-51.
Updated Guidelines for Using Interferon Gamma Release Assays to Detect Mycobacterium tuberculosis Infection—United States, 2010. Centers for Disease Control and Prevention website. Available at:
http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5905a1.htm
. Published June 2010. Accessed August 9, 2010.
12/16/2011 DynaMed's Systematic Literature Surveillance
http://www.ebscohost.com/dynamed/what.php: Sterling T, Villarino E, Borisov A, et al. Three months of rifapentine and isoniazid for latent tuberculosis infection.
N Engl J Med. 2011;365(23):2155.
Last Reviewed September 2011