Global Health: Tuberculosis Overview

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  • What is tuberculosis (TB)?
    • Tuberculosis (TB) is a disease caused by bacteria called Mycobacterium tuberculosis. The bacteria can attack any part of the body, but they usually attack the lungs.
  • What is the TB skin test?

    • The TB skin test is one way to determine if a person has TB infection. Although there is more than one TB skin test, the preferred TB skin test is the Mantoux test, which also is called the PPD skin test.

      For this test, a small amount of testing material is placed just below the top layers of skin, usually on the arm. Two to three days later, a health care worker checks the arm to see if a bump has developed and measures the size of the bump. If the bump is of a certain size then the person is presumed to have TB infection.

      Because a TB skin test cannot distinguish between latent TB infection and active TB disease, a health care worker will want to determine if the person has active TB disease. This is done by using several other tests, including a chest X-ray and a test of a person's mucus coughed up from the lungs.

      TB often is more difficult to diagnose in HIV-positive people than in HIV-negative people.  The skin test might not be a reliable way to determine if people living with HIV/AIDS have TB. For HIV-positive people, chest X-rays and sputum cultures are recommended to determine if they have active TB. It also is recommended that HIV-positive people receive a skin test every six to 12 months, depending on their risk of coming into contact with TB bacteria.

  • How is TB disease treated?

    • TB can almost always be cured with medicine. Known as “first-line” anti-TB drugs, some of the most common medicines used to treat TB are isoniazid (INH), rifampin (RIF), pyrazinamide (PZA) and ethambutol (EMB). There are also second-line drugs to treat TB including fluoroquinolones and injectable medicines such as capreomycin, kanamycin and amikacin

      Treatment for TB depends on whether a person has active TB or latent TB infection.  A person who has latent TB might be given preventive therapy. Preventive therapy aims to kill TB bacteria that currently are inactive to prevent them from causing active TB disease in the future. If a doctor decides a person should have preventive therapy, the usual prescription is a daily dose of INH.  The person takes INH for six to nine months -- possibly up to a year for some patients -- with periodic checkups to make sure the medicine is being taken as prescribed.

      However, when a patient has active TB, several different medicines are needed. Taking several drugs together will do a better job of killing all of the bacteria and preventing them from becoming resistant to the drugs. Many of the first-line medications are available in fixed-dose combinations (FDC), which combine several medications into a single tablet. The World Health Organization (WHO) strongly recommends the use of FDC tablets for TB treatment. Patients with active TB commonly receive a combination of several drugs -- most frequently INH plus two to three others -- usually for at least six months.  The patient will probably notice improvements only a few weeks after starting to take the drugs.

      It is very important that patients take their medicine correctly for the full length of treatment. If the medicine is taken incorrectly or treatment is stopped, the patient might become sick again and will be able to infect others with TB. In addition, if the treatment is not completed, the TB bacteria might become resistant to the medications and patients may develop multi-drug resistant TB or MDR-TB Although second-line medications do exist for MDR-TB treatment, this form of TB is usually harder to treat, requires patients to follow medication protocols for a longer period of time, and results in more adverse effects for patients.  In some cases, MDR-TB patients may develop resistance to second-line medications – this is known as extensively drug-resistant TB or XDR-TB

      In order to ensure adherence to medication and prevent the development of resistant strains of TB, many public health authorities recommend DOTS, or directly observed treatment, short-course, where a health care worker ensures that patients are taking their treatment regimens properly. Regular checkups are needed to monitor treatment progression. Sometimes the medicines used to treat TB can cause side effects. It is important that people undergoing both preventive therapy and treatment for TB disease immediately inform a doctor if they begin having any unusual symptoms.

      The treatment of tuberculosis in people infected with HIV requires close monitoring. It is especially important for those who are co-infected with HIV and TB to discuss TB treatment options with a health care worker to avoid potential complications, because some commonly prescribed medications to treat TB can interact with some antiretroviral drugs. The standard treatment regimen for TB patients who previously have been treated for the disease also may differ. Re-treatment cases also should be closely monitored because they have a higher likelihood of drug resistance, making treatment more difficult.

  • What is DOTS and the global strategy to combat TB?

    • Developed in 1995, directly observed treatment, short-course, or DOTS, has been the internationally recommended strategy to control TB. DOTS aims to decrease TB-related morbidity, prevent TB deaths, and decrease TB transmission. To achieve these goals, DOTS has five major components:
       
      • Political commitment with increased and sustained financing;
      • Case detection through quality-assured bacteriology;
      • Standardized treatment with supervision and patient support;
      • An effective drug supply and management system; and
      • A monitoring and evaluation system, and impact measurement.

      In an effort to build upon the DOTS strategy, the Stop TB Partnership, a network of more than 500 international organizations, countries, donors from the public and private sectors, and nongovernmental and governmental entities, was established in March 2000 with the singular goal of eliminating TB. The World Health Organization (WHO) is a leading agency in the partnership and serves as its Secretariat.

      In 2006, WHO announced a more enhanced approach to TB control entitled “Stop TB Strategy.” This new strategy addressed the current challenges facing countries in responding to TB, specifically looking at how to continue scaling-up TB control activities, while also addressing the spread of TB and HIV co-infection and multi-drug resistant TB. Although DOTS remains at the core of the Stop TB Strategy, this more nuanced six-point strategy goes further than previous efforts to make TB control more comprehensive and effective. The Stop TB Strategy includes the following primary goals:

      • Pursue high-quality DOTS expansion and enhancement;
      • Address TB/HIV co-infection, multidrug-resistant tuberculosis (MDR-TB) and other challenges;
      • Contribute to health system strengthening;
      • Engage all care providers;
      • Empower people with TB, and communities; and
      • Enable and promote research.

  • What is multi-drug resistant TB (MDR-TB)?

    • TB bacteria can become resistant to one or more of the first-line drugs used to treat TB . Drug resistance can occur when TB patients do not adhere to their prescribed drug regimens, health professionals prescribe an incorrect treatment regimen, or an unreliable drug supply interrupts patients' treatment. This means that the drug can no longer kill the bacteria.

      Drug resistance is more common in people who have spent time with someone with drug-resistant TB disease; do not take their medicine regularly; do not take all of their prescribed medicine; develop TB disease after having taken TB medicine in the past; or come from areas where drug-resistant TB is common.

      When the TB bacteria become resistant to more than one drug, a condition known as multi-drug resistant TB (MDR-TB) develops.  People with MDR-TB disease must be treated with specific second-line drugs that often are much more expensive than conventional therapy and cause more severe side effects. In addition, some people with MDR-TB disease must see a TB expert who can closely observe their treatment to ensure it is effective. It is important to note that patients with MDR-TB can sometimes develop resistance to second-line drug therapies as well, a condition known as extensively drug-resistant TB or XDR-TB.

      People who have spent time with someone with MDR-TB disease can become infected with TB bacteria that are resistant to several drugs. If they have a positive skin test reaction, they might be given preventive therapy. This is very important for people who are at high risk of developing MDR-TB disease, such as children and people living with HIV.

  • What is extensively drug-resistant TB (XDR-TB)?

    • Extensively drug-resistant tuberculosis (XDR-TB) is a relatively rare type of multi-drug resistant TB (MDR-TB) that is resistant to almost all drugs commonly used to treat drug-susceptible, or regular, TB. TB usually can be treated with a course of four standard drugs also known as first-line drugs. If these drugs are taken incorrectly or prescribed improperly, MDR-TB can develop. MDR-TB can be treated with second-line drugs that are more expensive and often are accompanied by more side effects-- treatment is also much longer than treatment for regular TB. If second-line drugs are taken incorrectly or prescribed improperly, XDR-TB can develop, leaving few treatment options available.

      The World Health Organization (WHO)'s Global Task Force on XDR-TB in October 2006 updated the definition of XDR-TB.  The definition also was published in the December 2006 in the Journal of the American Medical Association.  XDR-TB is defined as TB that is resistant to at least the two most powerful first-line TB drugs -- isoniazid and rifampin, also known as rifampicin -- as well as the second-line class of drugs known as fluoroquinolones and at least one of three injectable second-line drugs.  The injectable second-line drugs are capreomycin, kanamycin and amikacin.

  • How do people contract XDR-TB?

    • Drug-susceptible TB and extensively drug-resistant TB (XDR-TB) are spread the same way. Pulmonary TB, or TB that affects the lungs, can be spread from an infected person to an uninfected person through any action that transmits germs into the air -- including coughing, sneezing, and talking. In some cases, if the germs come from someone who has XDR-TB, the bacteria already might be drug resistant.

      A second way of developing XDR-TB is when someone who already has TB develops resistance to drugs. This can happen when someone who has TB does not take the full course of treatment or if treatment is mismanaged in some other way, such as health care workers prescribing the incorrect treatment or an interruption in the supply of drugs.

  • What are the symptoms of XDR-TB?

    • The symptoms of extensively drug-resistant TB (XDR-TB) do not differ from regular TB. Symptoms vary according to which part of the body is infected.  Pulmonary TB often is characterized by a persistent cough with thick, cloudy mucous -- or sputum -- that can contain blood. Other symptoms associated with TB are: night sweats and chills; fatigue and muscle weakness; weight loss; and, in some cases, shortness of breath and chest pain.

  • How is XDR-TB diagnosed and how long does it take?

    • If a person suspects they have TB or extensively drug-resistant TB (XDR-TB) or suspects exposure, he or she should consult a doctor or a local clinic. If the person has a cough, he or she will be asked to provide a sample of sputum for testing. Several other tests will be performed, including a skin test and a chest radiograph.

      If TB bacteria are found in the sputum, the diagnosis of TB can be made in a day or two, but this finding will not be able to distinguish between drug-susceptible TB and drug-resistant TB. To determine drug susceptibility, the bacteria need to be grown and tested in a laboratory. Final diagnosis for TB, especially for XDR-TB, could take six to 16 weeks.

  • Can XDR-TB be treated and cured?

    • Yes, in some cases. Several countries with good TB control programs have shown that cure is possible for up to 30% of people affected by extensively drug-resistant TB (XDR-TB).  But successful outcomes depend greatly on the extent of the drug resistance, the severity of the disease, and whether the person with XDR-TB has a weakened immune system.  Early diagnosis and treatment is important.

  • Is XDR-TB a new phenomenon?

    • For a few years, isolated cases of very highly resistant TB that would be called extensively drug-resistant (XDR-TB) under current definitions were reported in a few different locations worldwide. Recently, regular surveys of drug resistance in an increasing number of countries and improvements in laboratory capacity have resulted in more cases of drug-resistant TB being detected. This has led to the problem being more closely examined and given a name.

  • How is TB spread?

    • TB is spread through the air from one person to another.  When an infectious person coughs, sneezes, talks, or spits, they can propel TB germs, known as bacilli, into the air. People nearby might breathe in these bacteria and become infected.

      When a person breathes in TB bacteria, the bacteria can settle in the lungs and begin to multiply.  From there, they can move through the blood to other parts of the body, like the kidney, spine, and brain.

      TB in the lungs (referred to as pulmonary TB) or throat can be infectious.  This means that the bacteria can be spread to other people.  TB in other parts of the body (referred to as extrapulmonary TB) usually is not infectious.

      If left untreated, a person who has TB and is symptomatic will infect on average between 10 to 15 people every year according to the World Health Organization (WHO).

  • Why is there growing concern about XDR-TB?

    • The medical community in recent years has grown increasingly worried about extensively drug-resistant TB (XDR-TB). Rising numbers of XDR-TB cases and limited treatment options considerably exacerbate deaths from XDR-TB. The association of XDR-TB with HIV also has been a reason for concern since co-infected patients have a high mortality rate. Furthermore, many scientists fear that with the emergence of XDR-TB, the TB bacilli may mutate to a virtually un-treatable strain.

  • How common is XDR-TB?

    • Because extensively drug-resistant TB (XDR-TB) is a recently identified, rare phenomenon, it is difficult to determine how prevalent it is. The World Health Organization (WHO) estimates that in 2007, there were almost half a million cases of MDR-TB, which generally is a precursor for XDR-TB, and that 55 countries and territories had reported at least one case of XDR-TB by the end of 2008. Additional research is currently being conducted to get a better understanding of how many people are affected by XDR-TB.

      It is important to note that TB and XDR-TB appear to have similar rates of transmission. Just as with regular TB, the spread of XDR-TB bacteria depends on factors such as the number and concentration of infectious people in any one place and the presence of people with a higher risk of being infected (such as those with HIV/AIDS).

  • Can the BCG TB vaccine prevent XDR-TB?

    • The BCG vaccine prevents severe forms of TB in children, and it is likely that the vaccine would have the same effect in preventing TB even if children are exposed to extensively drug-resistant TB (XDR-TB).  However, it has limited effectiveness for preventing TB in adults. Therefore, the effect of BCG against XDR-TB likely would be very limited. New vaccines are urgently needed, and the World Health Organization (WHO) and members of the Stop TB Partnership are actively working on new vaccines.

  • What is the link between XDR-TB and HIV/AIDS? Do most people living with HIV-TB have XDR-TB?

    • TB is one of the most common infections in people living with HIV/AIDS. People living with HIV are at greater risk of becoming infected with extensively drug-resistant TB (XDR-TB) compared with people without HIV because of their compromised immune systems.

      If there are large numbers of HIV-positive people in places where XDR-TB is common, then there will be a strong link between XDR-TB and HIV.  The majority of people with HIV who develop TB will have drug-susceptible TB and can be treated with standard first-line TB drugs. For those with HIV, treatment with antiretroviral drugs likely will reduce the risk of contracting XDR-TB, just as it does with ordinary TB.

  • What are the links between HIV and TB?

    • HIV/AIDS and TB are so closely connected that the terms "co-epidemic" or "dual epidemic" often are used to describe their relationship. The dual epidemic often is called TB/HIV or HIV/TB. HIV affects the immune system and increases the likelihood that people will acquire new TB infection. HIV also can facilitate both the progression of latent TB infection to active disease and relapse of the disease in previously treated patients. TB is one of the leading causes of death in HIV-positive people.

  • How many people are co-infected with TB and HIV?

    • An estimated one-third of people living with HIV/AIDS worldwide are co-infected with TB. The majority of people who are co-infected with both diseases live in sub-Saharan Africa.

  • What is the impact of co-infection with TB and HIV?

    • Each disease speeds up the progress of the other, and TB considerably shortens the survival time of people living with HIV/AIDS. TB is a leading cause of death among people who are HIV-positive. People who are co-infected with HIV and TB are up to 50 times as likely to develop active TB in a given year as people who are HIV-negative. HIV infection is the greatest risk factor for the progression of latent TB into active TB, and TB bacteria can accelerate the progress of HIV.

      Many HIV-positive people in developing countries develop TB as the first sign of the later stages of the disease. The two diseases represent a deadly combination because they are more destructive together than either disease alone:
          • TB is harder to diagnose in HIV-positive people;
          • TB progresses faster in HIV-positive people;
          • TB in HIV-positive people is almost certain to be fatal if undiagnosed or left untreated; and
          • TB occurs earlier in the course of HIV infection than many other opportunistic infections.

  • Is quarantine required or permitted as a preventive measure?

    • Quarantine regulations for those exposed to an individual with infectious TB vary by situation and across regions of the world. Quarantine is not necessary if exposed to latent (non-infectious) TB. (Quarantine is the separation and containment of uninfected individuals who have been, or may have been, exposed to an infectious agent in order to limit or prevent exposure of an infectious agent to uninfected individuals.)

  • Is isolation required for the patient?

    • For patients who have active TB and are infectious, isolation is a common practice used by many hospitals and healthcare facilities to prevent the spread of the disease. On the other hand, patients who have latent TB infection do not require isolation. (Isolation is the separation and confinement of infected individuals, or those likely to be infected, in order to limit or prevent exposure of an infectious agent to uninfected individuals.)

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    • FAQ 3 answer here

  • Is there a vaccine for TB?

    • The Bacille Calmette-Guerin (BCG) vaccine currently is the only vaccine available for TB and was first used in 1921. The World Health Organization (WHO) estimates that the degree of efficacy of the vaccine varies greatly and seems to wane with age. The vaccine is recommended for infants and young children in countries where TB is common, as it is most effective in protecting these groups from severe forms of the disease. In general, the vaccine is unable to prevent most contagious forms of the disease in adults and is especially not recommended for those who have compromised immune systems or are pregnant.

      BCG is not widely used in the United States or Northern Europe. However, it is used in many developing countries.

      A spectrum of innovative new approaches has been applied to TB vaccine development during the last decade and several new TB candidate vaccines now are in clinical trials or at late stages of preclinical development.

  • What is latent TB infection?

    • Most people who become infected with TB are able to fight the bacteria and stop them from multiplying. In many of these people, the bacteria become dormant. This is called latent TB infection.  People with latent TB infection usually have a positive skin test reaction, but have no symptoms and cannot spread TB to others.

      TB bacteria remain alive in the body of those who have latent TB and can become active at a later point in time, if treatment is not received. The World Health Organization (WHO) estimates that approximately 5% to 10% of individuals infected with the TB bacteria actually become sick with the disease during their lifetime.  For persons whose immune systems are weak, particularly those with HIV, the risk of developing active TB disease is considerably higher than for persons with normal immune systems. This is because in people who have weakened immune systems, the dormant TB bacteria can reactivate, thereby changing the person’s status from latent infection to active disease.

  • What is active TB disease?

    • TB bacteria become active if the immune system cannot stop them from multiplying and the bacteria can cause active TB disease. People with active TB disease can spread the disease to others.  Those with active TB will often exhibit symptoms such as heavy coughing, fatigue, chills, and fever. Some people develop TB disease soon after becoming infected with the bacilli, before their immune system can fight the TB bacteria.  Other people might get sick later, when their immune systems become weak for some reason.  Most people infected with TB do not develop active TB disease and instead have what is called latent TB.

  • How much of a threat is TB?

    • In 1993, the World Health Organization (WHO) declared TB to be a global health emergency. According to the WHO, each year, an estimated eight million to 10 million people contract the disease and about two million people die from it.  About one-third of the world's population -- or approximately two billion people -- carry the TB bacteria but most never develop the active disease, a condition referred to as latent TB. Between 5% and 10% of people infected with latent TB become sick or infectious at some point during their lives, a condition referred to as active TB.

  • What are some other names used for TB?
    • The following are various names by which TB has been referred to over time:
      • Consumption
      • Wasting disease
      • White plague
      • Phthisis
      • Scrofulaz
      • King’s evil
      • Pott’s disease
      • Miliary TB
      • Tabes mesenterica
      • Koch’s Disease
  • What are some of the symptoms of TB disease?
    • People with latent TB infection do not have symptoms of TB and cannot spread TB to others. On the other hand, people with active TB disease often exhibit symptoms and can spread TB.  These symptoms may include:
      • A bad cough that lasts longer than two weeks;
      • Chest pain;
      • Coughing up blood or sputum;
      • Weakness or fatigue;
      • Weight loss;
      • No appetite;
      • Chills;
      • Fever; or
      • Sweating at night.
  • How is TB diagnosed?

    • TB can be diagnosed using a variety of methods including Mantoux tuberculin skin tests (TST), blood tests, culture tests (bacteriology), and chest x-rays. Because some of these tests are unable to differentiate between latent TB infection and active TB disease, they are often used in conjunction with one another or with other diagnostic tools.

      It is important to note that in HIV-positive populations, TB is particularly difficult to accurately detect because these individuals tend to be severely immuno-compromised and often cannot mount a strong enough immune response so as to be detected by many common diagnostic tools.

      Diagnosing TB in resource-poor setting can be challenging due to the limited diagnostic technologies available in these regions. In particular, extrapulmonary TB (TB in any other part of the body besides the lungs), which generally requires relatively sophisticated diagnostic methods, is much harder to detect in these regions.