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World Tuberculosis Day, a worldwide event that is observed on March 24th every year, aims to build public awareness about the global epidemic of tuberculosis and the efforts to prevent and treat this disease.  Even today in 2017, TB continues to be a major cause of morbidity and mortality, primarily in low-income and middle-income countries.

On March 24, 1882, Dr. Robert Koch announced the discovery of the causative agent of tuberculosis (TB), an airborne infectious disease caused by organisms of the Mycobacterium tuberculosis complex. M. tuberculosis, in spite being a pulmonary pathogen, can cause disease throughout the body. TB patients are rationally classified as having latent TB infection (LTBI), which is an asymptomatic and non-transmissible state, or active TB disease.

Epidemiology of TB

  • 1/3rd of the world’s population is infected with tuberculosis (TB).  In 2015, 10.4 million people developed active TB disease, out of which, 1.8 million people died due to the disease. The burden of TB is heterogeneously distributed. For e.g., TB incidence is >250-fold higher in South Africa (834 cases per 100,000 population per year) than in the United States (3 cases per 100,000 population per year).
  • Active TB disease develops at a very high rate in exposed infants, at a lower rate in children at 2–10 years of age; but the risk once again rises during the adolescence years and plateaus around 25 years of age, lasting throughout adult life.
  • The incidence of active TB disease is approximately two fold higher in men than in women.
  • Ongoing transmission of M. tuberculosis infection [Firdessa R et al., 2013] and LTBI reactivation [Reed MB et al., 2009] are globally responsible for TB disease.
  • Among major known risk factors for TB are HIV infection, undernutrition and indoor air pollution.  Other risk factors for TB include type 2 diabetes mellitus, excessive alcohol (both of which roughly triple the risk of TB) and smoking (which doubles the risk). Thus, addressing these social and behavioral determinants could help to expand the current biomedical paradigm for TB control.

Symptoms OF TB

In spite of harbouring the bacteria in your body you might not become sick, depending on your immune system.

Latent TB: It is an asymptomatic condition. It can go from being inactive to active TB, so treatment is vital for the person with latent TB.

Active TB: This condition makes you sick and can spread to others. Signs and symptoms of active TB include:

  • Coughing up blood/sputum
  • Coughing that lasts three weeks or longer
  • Chest pain
  • Unintended weight loss
  • Overtiredness
  • Fever
  • Night sweats
  • Anxieties
  • Anorexia (loss of appetite)

TB might also affect other organs of the body, including the kidneys, spine or brain. The signs and symptoms differ according to the organ affected with TB.

Diagnosis & Treatment

The choice of a diagnostic tool for TB depends on the purpose of testing (detecting LTBI, active TB disease or drug resistance).

LTBI

Two tests are available for the identification: the tuberculin skin test (TST) and the Interferon Gamma Release Assay (IGRA).  The IGRA is distinguished between BCG-induced and M. tuberculosis infection-induced positive TST responses [Pai M et al., 2014].

Active TB disease

Four main technologies are used for identification: imaging techniques are used for screening (chest X rays and PET-CT), whereas microscopy (sputum smears), culture-based and molecular tests requires a microbiological diagnosis.

Drug resistance

For drug resistance detection – phenotypic, culture-based (i.e., testing the capability of bacteria to survive in the presence of anti TB drugs) and molecular-based (detection of genetic mutations in the bacteria that bestow drug resistance) methods are used.

In children the diagnosis of TB is difficult as currently only Xpert MTB/RIF assay is commonly available to assist with the diagnosis of pediatric TB.

Treatment

LTBI

LTBI treatment regimens as suggested by the WHO include 6–9 months of isoniazid, 3 months of rifapentine plus isoniazid, 3–4 months of isoniazid plus rifampicin or 3–4 months of rifampicin alone145.  All regimens are known to be efficacious [WHO, 2014; Getahun H et al., 2015], but patient obedience can be poor with the longer regimens [Landry J et al., 2008].

Active drug-sensitive TB disease

For active drug-sensitive TB disease: a minimum of 6 months of therapy with rifampicin, isoniazid, pyrazinamide and ethambutol during the first 2 months (the intensive phase of treatment), followed by isoniazid and rifampicin for 4 months (the continuation phase) [WHO, 2010; Nahid P et al., 206].  The effectiveness of the treatment is usually supervised by testing for repeat sputum smears, cultures and chest X rays.

Prevention

  • TB education is necessary for people across the globe.
  • Identifying and treating the individuals with TB so as to prevent the transmission from an affected individual to a healthy individual.
  • Preventing active TB development in the individuals with latent TB.
  • Pasteurization of milk to prevent bovine TB.
  • The vaccine Bacillus Calmette-Guerin (BCG) has shown to provide protection in children against disseminated forms of TB.  Although it has been ineffective in adults against pulmonary TB.
  • Doctors and other health care workers, who provide care for patients with TB, must follow infection control procedures to ensure that TB infection is not passed from one person to another.
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