What is Tuberculosis (TB)?

Tuberculosis (TB) is a disease caused by bacteria called Mycobacterium tuberculosis that can affect various parts of the body, but most often the lungs. The symptoms of TB may include cough, fever, night sweats, weight loss and coughing up blood. These symptoms may develop gradually over many months resulting in a delay in seeking care, which may consequently lead to the transmission of bacteria to others.

When people with TB cough, sneeze, or spit, they propel germs into the air, and someone else only needs to inhale a few of these germs to become infected. People ill with TB can infect up to 10-15 other people through close contact. Without proper treatment up to two thirds of those infected with TB will die.

In 2011, there were an estimated 8.7 million new cases of TB in the world and 1.4 million deaths. India and China together account for almost 40% of the world’s TB cases. About 60% of cases are in the Southeast Asia and Western Pacific regions. One third of people estimated to have TB are either not covered for proper diagnosis or treatment by current health systems or are not reported.

But the good news is that the disease is curable and preventable if properly diagnosed and treated. The World Health Organization is actively pursuing a goal to reduce TB deaths and prevalence by 50% by 2015 through its Stop TB Strategy and in partnership with the Global Plan to Stop TB.

Between 2010 and 2011, new cases of TB have decreased at a rate of 2.2%. In addition, the TB mortality rate has dropped 41% since 1990, and the world is on track to achieve the WHO’s global target of a 50% reduction by 2015.

Latent TB

When TB bacteria enter our body we develop an immune response to stop the spread of infection and kill the bacteria. But not all bacteria are necessarily eliminated and can remain dormant for years, which is known as latent TB. Latent TB is not contagious and does not transmit to others, but it can reactivate in the future, especially if our immune system weakens (e.g., if we get cancer, HIV, or use immunosuppressant-like steroids). Thankfully only 10% of latent TB develops into active TB.

Testing for latent TB should be performed for individuals suspected of new infection. This includes all close contacts of the patient such as those living in the same household, as well as healthcare workers. The goal of testing is to identify individuals who are at increased risk of development of the disease and would benefit from treatment of latent infection.

Testing for latent TB in the absence of risk factors is not advised. In fact, universal testing would lead to a high rate of false positive tests. This is why we do not recommend routine screening for children entering school, daycare, or camps.

References:

• Driver CR, et al. “Tuberculin skin test screening in school children in the United States.” Pediatrics. 1996; 98(1): 97.
• www.uptodate.com/contents/clinical-manifestations-and-evaluation-of-pulmonary-tuberculosis
• www.who.int/topics/tuberculosis/en/