Introduction
Tuberculosis (TB) is a chronic or acute bacterial infection that primarily attacks the lungs, but which may also affect the kidneys, bones, lymph nodes, and brain. The disease is caused by Mycobacterium tuberculosis, a rod-shaped bacterium. Symptoms of TB include coughing, chest pain, shortness of breath, loss of appetite, weight loss, fever, chills, and fatigue. Children and people with weakened immune systems are the most susceptible to TB. Half of all untreated TB cases are fatal.
In 1993 the World Health Organization (WHO) declared TB to be a global emergency, the first such designation ever made by that organization. According to WHO, one individual becomes infected with TB every second, and every year 8 million people contract the disease (Andrews, 1996). Tuberculosis causes 2 million deaths a year. WHO predicts that between 2000 and 2020, nearly 1 billion people will become infected with the TB bacteria and 35 million people will die from the disease.
Pathology and Pathophysiology
Tuberculosis is spread by airborne droplet nuclei, which are particles of 1–5 um in diameter that contain Mycobacterium tuberculosis (Andrews, 1996). Because of their small size, the particles can remain airborne for minutes to hours after expectoration by people with pulmonary or laryngeal tuberculosis during coughing, sneezing, singing, or talking. The infectious droplet nuclei are inhaled and lodge in the alveoli in the distal airways. M tuberculosis is then taken up by alveolar macrophages, initiating a cascade of events that results in either successful containment of the infection or progression to active disease (primary progressive tuberculosis). Although the risk of development of active disease varies according to time since infection, age, and host immunity, the estimated lifetime risk of disease for a newly infected young child is 10%, with roughly half of that risk occurring in the first 2 years after infection (Andrews, 1996)....
