Tuberculosis

October 2010

“TB” is short for tuberculosis. TB disease 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.

How TB Spreads:

TB is spread through the air from one person to another. The TB bacteria are put into the air when a person with active 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

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 active TB disease.

  • Latent TB Infection

    TB bacteria can live in your body without making you sick. This is called latent TB infection (LTBI). 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. The only sign of TB infection is a positive reaction to the tuberculin skin test or special TB blood test. 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 get 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. TB disease will make you sick. People with TB disease may 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 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

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.

How Do You Evaluate Persons Suspected of Having TB Disease?

A complete medical evaluation for TB includes the following:

  1. Medical History

    Clinicians should ask about the patient’s history of TB exposure, infection, or disease.

  2. Physical Examination

    A physical exam can provide valuable information about the patient’s overall condition and other factors that may affect how TB is treated, such as HIV infection or other illnesses.

  3. Test for TB Infection

    The Mantoux tuberculin skin test (TST) or the special TB blood test can be used to test for M. tuberculosis infection.this is important in children < 5years of age. It has limited value in adult patients because of the high burden of TB in our population. Additional tests are required to confirm TB disease.

  4. Chest Radiograph

    Lesions may appear anywhere in the lungs .These abnormalities may suggest TB, but cannot be used to definitively diagnose TB.

  5. Diagnostic Microbiology

    The presence of acid-fast-bacilli (AFB) on a sputum smear or other specimen often indicates TB disease. Acid-fast microscopy is easy and quick, but it does not confirm a diagnosis of TB because some acid-fast-bacilli are not M. tuberculosisA culture [growing the bacteria in special lab media] is done on initial samples to confirm the diagnosis. Innovative molecular tests have rapidly reduced the time to detection of TB. They have reduced the time to detection to days instead of weeks or months.These tests called PCR [polymerase chain reactions] can pick up the gentic make up of the TB bacillus directly from a range of clinical specimens [except blood]as well as detecting those genes that code for drug resistant TB.

  6. Drug Resistance

    For all patients, the initial M. tuberculosis isolate should be tested for drug resistance. It is crucial to identify drug resistance as early as possible to ensure effective treatment. Drug susceptibility patterns should be repeated for patients who do not respond adequately to treatment or who have positive culture results despite 3 months of therapy.

What is multidrug-resistant tuberculosis (MDR TB)?

Multidrug-resistant TB (MDR TB) is TB that is resistant to at least two of the best anti-TB drugs, isoniazid and rifampicin. These drugs are considered first-line drugs and are used to treat all persons with TB disease.

What is extensively drug resistant tuberculosis (XDR TB)?

XDR TB is resistant to first-line and secondline drugs, patients are left with treatment options that are much less effective.

XDR TB is of special concern for persons with HIV infection or other conditions that can weaken the immune system. These persons are more likely to develop TB disease once they are infected, and also have a higher risk of death once they develop TB.

How does drug resistance happen?

Resistance to anti-TB drugs can occur when these drugs are misused or mismanaged. Examples include when patients do not complete their full course of treatment; when health-care providers prescribe the wrong treatment, the wrong dose, or length of time for taking the drugs; when the supply of drugs is not always available; or when the drugs are of poor quality.

How Does HIV Infection Affect TB?

HIV infection is the most important known risk factor for progression from latent TB infection to TB disease. Progression to TB disease is often rapid among HIV-infected persons and can be deadly. In addition, TB outbreaks can rapidly expand in HIV-infected patient groups.

Human immunodeficiency virus (HIV) or the AIDS virus helps TB bacteria make you sick because it weakens your immune system. If you are infected with HIV and with TB bacteria, you have a very big chance of getting TB disease. The TB bacteria are much more likely to become active and attack your lungs and other parts of the body. All patients in TB clinics should be tested for HIV. This includes TB suspects, patients, and contacts.

Can TB be treated?

TB disease can be treated by taking anti TB medication. It is very important that people who have TB disease finish the medicine, and take the drugs exactly as they are told. If they stop taking the drugs too soon, they can become sick again. If they do not take the drugs correctly, the bacteria that are still alive may become difficult to treat with those drugs.

It is very important that you take your medicine as your doctor recommends. It takes at least six months to one year to kill all the TB bacteria.

Protect your family and friends from TB — take all your TB drugs!

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