Tuberculosis (TB) is a disease caused by a bacterium called Mycobacterium tuberculosis, which is spread through the air from one person to another. The bacteria are put into the air when a person with TB disease of the lungs or throat coughs, sneezes, speaks, or sings. People nearby may breathe in these TB bacteria and become infected (called latent TB infection).
Most people with latent TB infection do not know they have been infected, since it can only be detected with a TB skin test reaction or special TB blood test. People with latent TB infection do not feel sick, do not have any symptoms, and cannot spread TB bacteria to others. People with latent TB infection can take medicine so they will not develop TB disease.
Even without medicine, many people who have latent TB infection never develop active TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease. But in other people, especially people who have weak immune systems, the bacteria become active, multiply, and cause TB disease.
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TB bacteria become active if the immune system can't stop them from growing. The active bacteria begin to multiply in the body and cause TB disease. The bacteria attack the body and destroy tissue. If this occurs in the lungs (the most common site for TB disease), the bacteria can actually create a hole in the lung. Some people develop TB disease soon after becoming infected (within weeks) before their immune system can fight the TB bacteria. Other people may get sick years later, when their immune system becomes weak for another reason.
Symptoms of TB disease depend on where in the body the TB bacteria are growing. TB in the lungs may cause symptoms such as a bad cough that lasts 3 weeks or longer; pain in the chest; or coughing up blood or sputum (phlegm from deep inside the lungs). Other symptoms of TB disease are weakness or fatigue; weight loss; no appetite; chills; fever; or sweating at night.
Sometimes the TB bacteria are resistant to the medicines used to treat TB disease. This means that the medicine can no longer kill the bacteria. Multidrug-resistant TB, or MDR TB, is caused by bacteria that are resistant to two of the most important TB medicines: isoniazid and rifampicin. A more serious form of MDR TB is called extensively drug-resistant TB (XDR TB). XDR TB is a rare type of TB that is resistant to nearly all medicines used to treat TB disease.
Drug resistance is more common in people who have spent time with someone with drug-resistant TB disease; do not take their medicines as directed by their doctor or nurse; develop active TB disease again, after having taken TB medicines in the past; or come from areas of the world where drug-resistant TB is common. People with MDR TB or XDR TB must be treated with special medicines which may cause more side effects. Treatment takes much longer than regular TB, and people with MDR TB and XDR TB are at greater risk of dying from the disease.
The latest estimates of the global burden of TB show that in 2007, there were over 9 million new cases of TB with almost 2 million deaths from TB. In the United States, there were 13,299 TB cases reported from the 50 states and the District of Columbia (DC) for 2007, with over half of these cases occurring in foreign-born persons.
Close contacts, people who have spent time with someone who has infectious TB disease, are at high risk for TB infection. Close contacts may include family members, coworkers, or friends.
With increased international travel and a global marketplace, no region of the world is immune from outside influences. In the United States, latent TB infection and TB disease occur often among people born in areas of the world where TB is common, such as Asia, Africa, Russia, Eastern Europe, and Latin America.
People who work in health care facilities, such as clinics and hospitals, may be exposed to TB on the job. The risk of exposure depends on the number of persons with TB in the facility, the employee's duties, and the effectiveness of the infection control procedures in the facility.
Anyone who has latent TB infection can develop TB disease, but some people are at higher risk than others. HIV-infected people are at greatest risk. Other high-risk groups include people with medical conditions that are known to increase the risk for TB (patients on prolonged therapy with corticosteroids and other immunosuppressive therapy, silicosis, diabetes mellitus, severe kidney disease, certain types of cancer, and certain intestinal conditions); people recently infected with TB bacteria (within the past 2 years); infants and children younger than 4 years; and people who inject illegal drugs.
Yes, but there are a number of obstacles to eliminating TB:
- TB does not stop at U.S. borders (nor can prevention efforts);
- some think TB is a disease of the past;
- generally, people are unaware of TB symptoms;
- TB infection can be latent in the body for years before turning into TB disease;
- many people with or at risk for active TB disease do not have access to adequate health care.
- INFORM viewers of the symptoms and risk factors of TB
- REMIND viewers that anyone can get TB, not only immigrants and poor people, but other people as well.
- EXPLAIN to viewers the difference between latent TB infection and active TB disease. Explain that a person with latent TB infection cannot infect another person.
- EXPLAIN that TB can only be transmitted though the air from a person with active TB disease to another person who breathes the same air in a confined space over a period of time.
- REMIND viewers that a bad cough should be checked by a doctor. Coughing could indicate many diseases, not just TB.
- REASSURE viewers that TB is treatable and curable.
- Angela spent 2 years in Africa in the Peace Corps just after graduating from college 10 years ago. She now works as an elementary school teacher in Denver, Colorado. She's very involved with her family, including a sister undergoing treatment for cancer. Angela has recently been losing weight without trying, and she has developed a really bad cough that keeps getting worse. This morning she started coughing up blood. Could Angela have TB? If so, could she have transmitted TB bacteria to the children in her class, to her family, or to her sick sister?
- Ben was diagnosed with TB while he was jail. He was started on medication and completed 1 month of drugs before he was released. He was given a one-week supply of medication and instructed to continue his treatment with the local health department. The health department sent an outreach worker to Ben's home address to ensure he continued his treatment; however, the woman who answered the door stated that Ben had left the area with no forwarding address. Six months later, Ben goes to the emergency room in another state because he is coughing and having pain in his chest. Could Ben now have drug-resistant TB?
- Page last reviewed: February 23, 2011
- Page last updated: February 23, 2011
- Content source:
- Centers for Disease Control and Prevention
- Page maintained by: Division of Public Affairs (DPA), Office of the Associate Director for Communication (OADC)