Tuberculosis

Tuberculosis (TB) is caused by bacteria called Mycobacterium tuberculosis. It most often affects the lungs. Tuberculosis is curable and preventable. About a one-third of the world’s populations has latent TB; this means a person has been infected by the TB bacteria but is not yet ill with disease and cannot spread the disease. TB is second greatest killer worldwide due to a single infectious agent with HIV/AIDS being first. Last year about 9 million people fell ill with TB and 1.5 million died from the disease. The deaths were in low and middle income countries, with women and children being affected the most.

“TB occurs in every part of the world. In 2013, the largest number of new TB cases occurred in the South-East Asia and Western Pacific Regions, accounting for 56% of new cases globally. However, Africa carried the greatest proportion of new cases per population with 280 cases per 100,000 population in 2013.” (CDC, 2013) There are about 22 countries that have reported cases; with some countries experiencing a decline in cases. Brazil and China are a few of the countries that experienced a sustained decline in TB cases over the past 20 years, with Cambodia cases fell by almost 50%. People who have HIV are 26 to 31 times more probable to become sick with TB; risks of active TB are also abundant in persons suffering from other illnesses or weaken immune system. There is also a risk of TB disease and death in those that are tobacco users.

Tuberculosis is spread from person to person through airborne droplets, when a person that is infected with TB coughs, sneezes, talks, and/or sings the TB germs is released into the air. Only a few germs are needed to be infected. The person must be in the same area an affected individual is in and inhale the droplets to be affected. Once the bacillus is inhaled into the lungs, the bacilli start to multiply causing lung inflammation also known as nonspecific pneumonitis. To cause an immune reaction the bacilli will travel through lymphatic system and become lodged in the lymph nodes. Lung inflammation causes the activation of the alveolar macrophages and neutrophils. Granulomas, new tissue masses of live and dead bacilli, are surrounded by macrophages, which form a protective wall. They then transform into a fibrous tissue mass, the central portion is called a ghon tubercle. The bacterial then necrotic, forming a cheesy mass, this mass may become calcified and form a collagenous scar. At this point, the bacteria become dormant and there is no further progression of the active disease. The disease can become active again by re-infection or activation of the dormant bacteria.

Tubercle bacilli in the lung tissue

TB can be classified as latent or active. TB that is latent is bacilli that are isolated with a tubercle and remain dormant, causing no symptoms. Active TB occurs when live bacilli escape into the bronchi or if the immune system is weaken by diseases such as HIV. A complete history, physical examination, tuberculin skin test (PPD), chest x-ray, acid-fast bacillus smear and sputum culture are used