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T U B E R C U L O S I S (TB)
Web Pages
TB Index              
Basic TB Facts
How TB Spreads
Latent TB Infection and TB Disease
  Latent TB Infection
TB Disease
         
TB Symptoms
TB Risk Factors
      Risk Factors
Persons who have been Recently Infected with TB Bacteria
Persons with Medical Conditions that Weaken the Immune System
     
Testing for TB Infection
Tuberculin skin test
      Positive skin test
Negative skin test
             
TB blood tests
      Positive IGRA
Negative IGRA
             
Who Should Get Tested for TB
Testing for TB in BCG-Vaccinated Persons
      Choosing a TB Test              
Diagnosis of Latent TB Infection or TB Disease
Diagnosis of TB Disease
Treatment for Latent TB Infection and TB Disease
      Drug Treatment for TB Disease              
Treatment for TB Disease
Treatment Completion
      TB and HIV Coinfection
Treatment
             
TB Vaccine (BCG)
      BCG Recommendations
Children
Health Care Workers
             
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Basic TB Facts
(TB) is caused by a bacterium 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.  
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How TB Spreads
  Diagram of TB spread by sneezing      

TB is spread through the air from one person to another. The TB 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 bacteria and become infected.

TB is NOT spread by

  • shaking someone’s hand
  • sharing food or drink
  • touching bed linens or toilet seats
  • sharing toothbrushes
  • kissing
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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 TB disease.
Latent TB Infection
TB bacteria can live in the body without making you sick. This is called 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. People with latent TB infection do not feel sick and do not have any symptoms. People with latent TB infection are not infectious and cannot spread TB bacteria to others. However, if TB bacteria become active in the body and multiply, the person will go from having latent TB infection to being sick with TB disease.
TB Disease

TB bacteria become active if the immune system can't stop them from growing. When TB bacteria are active (multiplying in your body), this is called TB disease. People with TB disease are sick. They may also be able to spread the bacteria to people they spend time with every day.

Many people who have latent TB infection never develop TB disease. 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.

For people whose immune systems are weak, especially those with HIV infection, the risk of developing TB disease is much higher than for people with normal immune systems.

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TB Symptoms
 
Signs and Symptoms of TB Disease

Symptoms of TB disease depend on where in the body the TB bacteria are growing. TB bacteria usually grow in the lungs (pulmonary TB). TB disease 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 TB disease are

  • weakness or fatigue
  • weight loss
  • no appetite
  • chills
  • fever
  • sweating at night

Symptoms of TB disease in other parts of the body depend on the area affected.

People who have latent TB infection do not feel sick, do not have any symptoms, and cannot spread TB to others.

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TB Risk Factors

Once a person is infected with TB bacteria, the chance of developing TB disease is higher if the person:

  • Has HIV infection;
  • Has been recently infected with TB bacteria (in the last 2 years);
  • Has other health problems, like diabetes, that make it hard for the body to fight bacteria;
  • Abuses alcohol or uses illegal drugs; or
  • Was not treated correctly for TB infection in the past
Risk Factors

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.

Overall, about 5 to 10% of infected persons who do not receive treatment for latent TB infection will develop TB disease at some time in their lives. For persons whose immune systems are weak, especially those with HIV infection, the risk of developing TB disease is much higher than for persons with normal immune systems.

Generally, persons at high risk for developing TB disease fall into two categories:

  • Persons who have been recently infected with TB bacteria
  • Persons with medical conditions that weaken the immune system
Persons who have been Recently Infected with TB Bacteria

This includes:

  • Close contacts of a person with infectious TB disease
  • Persons who have immigrated from areas of the world with high rates of TB
  • Children less than 5 years of age who have a positive TB test
  • Groups with high rates of TB transmission, such as homeless persons, injection drug users, and persons with HIV infection
  • Persons who work or reside with people who are at high risk for TB in facilities or institutions such as hospitals, homeless shelters, correctional facilities, nursing homes, and residential homes for those with HIV
Persons with Medical Conditions that Weaken the Immune System

Babies and young children often have weak immune systems. Other people can have weak immune systems, too, especially people with any of these conditions:

  • HIV infection (the virus that causes AIDS)
  • Substance abuse
  • Silicosis
  • Diabetes mellitus
  • Severe kidney disease
  • Low body weight
  • Organ transplants
  • Head and neck cancer
  • Medical treatments such as corticosteroids or organ transplant
  • Specialized treatment for rheumatoid arthritis or Crohn’s disease
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Testing for TB Infection
There are two kinds of tests that are used to detect TB bacteria in the body: the TB skin test (TST) and TB blood tests. These tests can be given by a health care provider or local health department. If you have a positive reaction to either of the tests, you will be given other tests to see if you have latent TB infection or TB disease.

Tuberculosis (TB) is a disease that is spread through the air from one person to another. There are two kinds of tests that are used to determine if a person has been infected with TB bacteria: the tuberculin skin test and TB blood tests.

A positive TB skin test or TB blood test only tells that a person has been infected with TB bacteria. It does not tell whether the person has latent TB infection (LTBI) or has progressed to TB disease. Other tests, such as a chest x-ray and a sample of sputum, are needed to see whether the person has TB disease.

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Tuberculin skin test:

The TB skin test (also called the Mantoux tuberculin skin test) is performed by injecting a small amount of fluid (called tuberculin) into the skin in the lower part of the arm. A person given the tuberculin skin test must return within 48 to 72 hours to have a trained health care worker look for a reaction on the arm. The health care worker will look for a raised, hard area or swelling, and if present, measure its size using a ruler.  Redness by itself is not considered part of the reaction.

The skin test result depends on the size of the raised, hard area or swelling. It also depends on the person’s risk of being infected with TB bacteria and the progression to TB disease if infected.

  • Positive skin test: Thismeans the person’s body was infected with TB bacteria.  Additional tests are needed to determine if the person has latent TB infection or TB disease.  A health care worker will then provide treatment as needed.
  • Negative skin test:  This means the person’s body did not react to the test, and that latent TB infection or TB disease is not likely.
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TB blood tests:

TB blood tests (also called interferon-gamma release assays or IGRAs) measure how the immune system reacts to the bacteria that cause TB.  An IGRA measures how strong a person’s immune system reacts to TB bacteria by testing the person’s blood in a laboratory.

Two IGRAs are approved by the U.S. Food and Drug Administration (FDA) and are available in the United States:

  1. QuantiFERON®–TB Gold In-Tube test (QFT-GIT)
  2. T-SPOT®.TB test (T-Spot)
  • Positive IGRA: This means that the person has been infected with TB bacteria.  Additional tests are needed to determine if the person has latent TB infection or TB disease. A health care worker will then provide treatment as needed.
  • Negative IGRA: This means that the person’s blood did not react to the test and that latent TB infection or TB disease is not likely. 

IGRAs are the preferred method of TB infection testing for the following:

  • People who have received bacille Calmette–Guérin (BCG). BCG is a vaccine for TB disease.
  •  People who have a difficult time returning for a second appointment to look for a reaction to the TST.
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Who Should Get Tested for TB
There is no problem with repeated IGRAs.

TB tests are generally not needed for people with a low risk of infection with TB bacteria.

Certain people should be tested for TB bacteria because they are more likely to get TB disease, including:

  • People who have spent time with someone who has TB disease
  • People with HIV infection or another medical problem that weakens the immune system
  • People who have symptoms of TB disease (fever, night sweats, cough, and weight loss)
  • People from a country where TB disease is common (most countries in Latin America, the Caribbean, Africa, Asia, Eastern Europe, and Russia)
  • People who live or work somewhere in the United States where TB disease is more common (homeless shelters, prison or jails, or some nursing homes)
  • People who use illegal drugs
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Testing for TB in BCG-Vaccinated Persons

People who were previously vaccinated with BCG may receive a TB skin test to test for TB infection. Vaccination with BCG may cause a positive reaction to a TB skin test. A positive reaction to a TB skin test may be due to the BCG vaccine itself or due to infection with TB bacteria.

A positive reaction to a TB skin test probably means you have been infected with TB bacteria if

  • You recently spent time with a person who has TB disease; or
  • You are from an area of the world where TB disease is very common (such as most countries in Latin America and the Caribbean, Africa, Asia, Eastern Europe, and Russia); or
  • You spend time where TB disease is common (such as homeless shelters, migrant farm camps, drug-treatment centers, health care clinics, jails, or prisons).

TB blood tests (IGRAs), unlike the TB skin test, are not affected by prior BCG vaccination and are not expected to give a false-positive result in people who have received BCG.

For children under the age of five, the TB skin test is preferred over TB blood tests.

A positive TB skin test or TB blood test only tells that a person has been infected with TB bacteria. It does not tell whether the person has latent TB infection or has progressed to TB disease. Other tests, such as a chest x-ray and a sample of sputum, are needed to see whether the person has TB disease.

Many people born outside of the United States have been BCG-vaccinated.

Choosing a TB Test
The person’s health care provider should choose which TB test to use. Factors in selecting which test to use include the reason for testing, test availability, and cost. Generally, it is not recommended to test a person with both a TST and an IGRA.
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Diagnosis of Latent TB Infection or TB Disease

If a person is found to be infected with TB bacteria, other tests are needed to see if the person has TB disease.

TB disease can be diagnosed by medical history, physical examination, chest x-ray, and other laboratory tests.  TB disease is treated by taking several drugs as recommended by a health care provider. 

If a person does not have TB disease, but has TB bacteria in the body, then latent TB infection is diagnosed.  The decision about treatment for latent TB infection will be based on a person’s chances of developing TB disease.

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Diagnosis of TB Disease

People suspected of having TB disease should be referred for a medical evaluation, which will include 

  • Medical history,
  • Physical examination,
  • Test for TB infection (TB skin test or TB blood test),
  • Chest radiograph (X-ray), and
  • Appropriate laboratory tests
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Treatment for Latent TB Infection and TB Disease

If you have latent TB infection but not TB disease, your health care provider may want you be treated to keep you from developing TB disease. Treatment of latent TB infection reduces the risk that TB infection will progress to TB disease. Treatment of latent TB infection is essential to controlling and eliminating TB in the United States. The decision about taking treatment for latent TB infection will be based on your chances of developing TB disease.

Drug Treatment for TB Disease

TB disease can be treated by taking several drugs, usually for 6 to 9 months. It is very important to finish the medicine, and take the drugs exactly as prescribed. If you stop taking the drugs too soon, you can become sick again. If you do not take the drugs correctly, the germs that are still alive may become resistant to those drugs. TB that is resistant to drugs is harder and more expensive to treat.

People with latent TB infection have TB bacteria in their bodies, but they are not sick because the bacteria are not active. People with latent TB infection do not have symptoms, and they cannot spread TB bacteria to others. However, if TB bacteria become active in the body and multiply, the person will go from having latent TB infection to being sick with TB disease. For this reason, people with latent TB infection are often prescribed treatment to prevent them from developing TB disease. Treatment of latent TB infection is essential for controlling and eliminating TB in the United States.

Because there are less bacteria in a person with latent TB infection, treatment is much easier. Four regimens are approved for the treatment of latent TB infection. The medications used to treat latent TB infection include:

  • isoniazid (INH)
  • rifampin (RIF)
  • rifapentine (RPT)

Certain groups of people (such as people with weakened immune systems) are at very high risk of developing TB disease once infected with TB bacteria. Every effort should be made to begin appropriate treatment and to ensure completion of the entire course of treatment for latent TB infection.

Regimens for treating TB disease have an initial phase of 2 months, followed by a choice of several options for the continuation phase of either 4 or 7 months (total of 6 to 9 months for treatment).

It is very important that people who have TB disease finish the medicine, taking the drugs exactly as prescribed. If they stop taking the drugs too soon, they can become sick again; if they do not take the drugs correctly, the TB bacteria that are still alive may become resistant to those drugs. TB that is resistant to drugs is harder and more expensive to treat.

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Treatment for TB Disease

TB bacteria become active (multiplying in the body) if the immune system can't stop them from growing. When TB bacteria are active, this is called TB disease. TB disease will make a person sick. People with TB disease may spread the bacteria to people with whom they spend many hours.

TB disease can be treated by taking several drugs for 6 to 9 months. There are 10 drugs currently approved by the U.S. Food and Drug Administration (FDA) for treating TB. Of the approved drugs, the first-line anti-TB agents that form the core of treatment regimens include:

  • isoniazid (INH)
  • rifampin (RIF)
  • ethambutol (EMB)
  • pyrazinamide (PZA)
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Treatment Completion

Treatment completion is determined by the number of doses ingested over a given period of time. Although basic TB regimens are broadly applicable, there are modifications that should be made under special circumstances (such as people with HIV infection, drug resistance, pregnancy, or treatment of children).

TB and HIV Coinfection

Even though fewer people in the United States have tuberculosis (TB), it remains a serious threat, especially for people living with HIV. People living with HIV are more likely than others to become sick with TB. Worldwide, TB is one of the leading causes of death among people living with HIV.

Without treatment, as with other opportunistic infections, HIV and TB can work together to shorten lifespan.

  • Someone with untreated latent TB infection and HIV infection is much more likely to develop TB disease during his or her lifetime than someone without HIV infection.
  • Among people with latent TB infection, HIV infection is the strongest known risk factor for progressing to TB disease.
  • A person who has both HIV infection and TB disease has an AIDS-defining condition.

People infected with HIV who also have either latent TB infection or TB disease can be effectively treated. The first step is to ensure that people living with HIV are tested for TB infection. If found to have TB infection, further tests are needed to rule out TB disease. The next step is to start treatment for latent TB infection or TB disease based on test results.

Treatment

Untreated latent TB infection can quickly progress to TB disease in people living with HIV since the immune system is already weakened. And without treatment, TB disease can progress from sickness to death.

Fortunately, there are a number of treatment options for people living with HIV who also have either latent TB infection or TB disease. Consult with your state or local health department for treatment options.

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TB Vaccine (BCG)
Bacille Calmette-Guérin (BCG) is a vaccine for tuberculosis (TB) disease. This vaccine is not widely used in the United States, but it is often given to infants and small children in other countries where TB is common. BCG does not always protect people from getting TB.
BCG Recommendations
In the United States, BCG should be considered for only very select people who meet specific criteria and in consultation with a TB expert. Health care providers who are considering BCG vaccination for their patients are encouraged to discuss this intervention with the TB control program in their area.
Children

BCG vaccination should only be considered for children who have a negative TB skin test and who are continually exposed, and cannot be separated from adults who

  • Are untreated or ineffectively treated for TB disease, and the child cannot be given long-term primary preventive treatment for TB infection; or
  • Have TB disease caused by strains resistant to isoniazid and rifampin.
Health Care Workers

BCG vaccination of health care workers should be considered on an individual basis in settings in which

  • A high percentage of TB patients are infected with TB  strains resistant to both isoniazid and rifampin;
  • There is ongoing transmission of drug-resistant TB strains to health care workers and subsequent infection is likely; or
  • Comprehensive TB infection-control precautions have been implemented, but have not been successful.

Health care workers considered for BCG vaccination should be counseled regarding the risks and benefits associated with both BCG vaccination and treatment of latent TB infection.

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