Questions and Answers About TB, 2007
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Introduction
What is TB?
Tuberculosis (TB) is a disease caused by bacteria called Mycobacterium
tuberculosis. The bacteria usually attack the lungs. But,
TB bacteria can attack any part of the body such as the kidney,
spine, and brain. If not treated properly, TB disease can be fatal.
TB disease was once the leading cause of death in the United States.
TB is spread through the air from one person to another. The bacteria
are put into the air when a person with active
TB disease of the lungs or throat coughs or sneezes. People
nearby may breathe in these bacteria and become infected.
However, not everyone infected with TB bacteria becomes sick.
People who are not sick have what is called latent
TB infection. People who have latent TB infection do
not feel sick, do not have any symptoms, and cannot spread TB to
others. But, some people with latent TB infection go on to get TB
disease.
People with active TB disease can be treated if they
seek medical help. Even better, most people with latent TB infection
can take medicine so that they will not develop active TB disease.
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Why is TB a problem today?
Starting in the 1940s, scientists discovered the first of several
medicines now used to treat TB. As a result, TB slowly began to
decrease in the United States. But in the 1970s and early 1980s,
the country let its guard down and TB control efforts were neglected.
As a result, between 1985 and 1992, the number of TB cases increased.
However, with increased funding and attention to the TB problem,
we have had a steady decline in the number of persons with TB since
1992. But TB is still a problem; more than 14,000 cases were reported
in 2005 in the United States.
This booklet answers common questions about TB. Please ask your
doctor or nurse if you have other questions about latent TB infection
or TB disease.
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How is TB spread?
TB is spread through the air from one person to another. The bacteria
are put into the air when a person with active TB disease of the
lungs or throat coughs or sneezes. People nearby may breathe in
these bacteria and become infected.
When a person breathes in TB bacteria, the bacteria can settle
in the lungs and begin to grow. From there, they can move through
the blood to other parts of the body, such as the kidney, spine,
and brain.
TB in the lungs or throat can be infectious. This means that the
bacteria can be spread to other people. TB in other parts of the
body, such as the kidney or spine, is usually not infectious.
People with active TB disease are most likely to spread it to
people they spend time with every day. This includes family members,
friends, and coworkers.
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What is latent TB infection?
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
- have no symptoms
- don't feel sick
- can't spread TB to others
- usually have a positive skin test reaction
or QuantiFERON-TB Gold test (QFT-G)
- may develop active TB disease if they do not receive treatment
for latent TB infection
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
and cause TB disease.
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What is active TB disease?
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 active TB disease. The bacteria attack the body and destroy
tissue. If this occurs in the lungs, the bacteria can actually create
a hole in the lung. Some people develop active TB disease soon after
becoming infected, before their immune system can fight the TB bacteria.
Other people may get sick later, when their immune system becomes
weak for another reason.
Babies and young children often have weak immune systems. People
infected with HIV, the virus that
causes AIDS, have very weak immune systems. Other people can have
weak immune systems, too, especially people with any of these conditions:
- substance abuse
- diabetes mellitus
- silicosis
- cancer of the head or neck
- leukemia or Hodgkin's disease
- severe kidney disease
- low body weight
- certain medical treatments (such as corticosteroid treatment
or organ transplants)
- specialized treatment for rheumatoid arthritis or Crohn’s 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 symptoms such as
- a bad cough that lasts 3 weeks or longer
- pain in the chest
- coughing up blood or sputum (phlegm from deep inside the lungs)
Other symptoms of active TB disease are
- weakness or fatigue
- weight loss
- no appetite
- chills
- fever
- sweating at night
The Difference Between Latent TB Infection and
Active TB Disease
A Person with Latent TB Infection |
A Person with Active TB Disease |
• Has no symptoms |
• Has symptoms that 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
- sweating at night |
• Does not feel sick |
• Usually feels sick |
• Cannot spread TB bacteria to
others |
• May spread TB bacteria to others |
• Usually has a positive skin test
or QuantiFERON-TB® Gold test |
• Usually has a positive skin test
or QuantiFERON-TB® Gold test |
• Has a normal chest x-ray and a
negative sputum smear |
• May have an abnormal chest
x-ray, or positive sputum smear or culture |
• Needs treatment for
latent TB infection to prevent active TB disease |
• Needs treatment to treat active
TB disease |
Last Modified: 06/26/2008
Last Reviewed: 05/18/2008 Content Source: Division of Tuberculosis Elimination
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
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