Understanding TB

What Causes TB?

TB is caused by bacteria (Mycobacterium tuberculosis) that mostly affect the lungs. TB is preventable, treatable and curable.

TB is spread through the air. When people with lung TB cough, sneeze or spit, they send TB germs into the air. To become infected, a person needs to inhale only a few of the germs.

About one-third of the world’s population has latent TB. With latent TB, people have been infected by TB bacteria but are not (yet) sick with the disease and cannot transmit it.  If they are diagnosed, the latent form of the disease can be treated and cured.  However, since they are a-symptomatic most people do not know they have TB.

Who is At Risk?

People who are most at risk include those with compromised immune systems, such as people living with HIV, malnutrition or diabetes, or people who use tobacco.  When a person develops active TB disease, the symptoms – cough, fever, night sweats, weight loss etc.) may be mild for many months.  This poses a risk for others around them if the person is not diagnosed until the disease has progressed and symptoms have worsened.

People with active TB can infect 10-15 other people through close contact over the course of a year. Without proper treatment, 45% of HIV-negative people with TB on average and nearly all HIV-positive people with TB will die.

How is TB Treated?

TB disease is treated with a standard six-month course of four antimicrobial drugs that are provided with information, supervision and support to the patient by a health worker or trained volunteer. Without such support, treatment adherence can be difficult and the disease can spread.  If medicines are prescribed and taken properly, more than 95% of TB cases can be cured.

What is Multidrug-resistant TB?

97% percent of TB cases worldwide respond to the standard treatment, but the world is not confronting the increasing resistance to drugs to tackle TB.  Multi-drug resistant tuberculosis (MDR-TB) is a form of TB caused by bacteria that do not respond to isoniazid and rifampicin, the two most powerful, first-line or standard anti-TB drugs.

Primary reasons why drug resistance occurs are inappropriate treatment, inappropriate or incorrect use of anti-TB drugs, poor patient adherence to treatment, or use of poor quality medicines.  In places that already have high levels of MDR- TB there are also significant levels of direct transmission of resistant TB bugs.

MDR-TB is treatable and curable by using second-line drugs.  However, second-line treatment options are limited and recommended medicines may not always be available or, if available, are cost prohibitive.  Injections and medicines can be required treatment for two years, making adherence a problem.  In addition, severe adverse drug reactions can develop, including loss of hearing.  Today with all these challenges only 25% of MDR- TB patients are getting diagnosed and treated and only 50% of these patients are treated successfully.

What is XDR-TB?

XDR-TB develops when there is severe drug resistance. It responds to very few drugs and it is often difficult to find the drug that can treat XDR-TB.  Approximately 480,000 people developed MDR-TB worldwide in 2014.  More than half of these cases were in India, the People’s Republic of China and the Russian Federation.  Estimates are that about 9.7% of MDR-TB cases had XDR-TB.  Treatment success for XDR- TB is only about 20%.