Overview of TB
In 1993, the World Health Organization (WHO) declared tuberculosis a global emergency. According to the WHO, worldwide incidence of tuberculosis (TB) may have peaked in 2005. Tuberculosis infection is responsible for more deaths than any other infectious disease. Once called consumption, TB is a highly contagious, persistent disease characterized by the formation of hard grayish nodules, or tubercles. The disease is most often caused by the bacterium Mycobacterium tuberculosis and usually occurs in the lungs (the initial site of infection), but it also can occur in other organs.
Because its signs and symptoms are easily confused with those of many other (usually respiratory) diseases, tuberculosis can be difficult to diagnose. Common symptoms are cough that is worse in the morning and may include hemoptysis (i.e., blood in the sputum), chest pain, night sweats, and breathlessness (dyspnea). Ninety percent of those infected with M. tuberculosis mount an effective immune response and never develop the disease.
Incidence and Prevalence of TB
Mycobacterial disease is one of the world's most difficult health problems. One-third of the population worldwide is infected with tuberculosis. Of these, 8 to 10 million develop active disease and according to the World Health Organization (WHO), 2 million die each year. It is the greatest cause of death in women of reproductive age; 900 million women are currently infected. Of these, 2.5 million will develop active disease and 1 million will die.
According to WHO, every year more than 1.5 million TB cases occur in sub-Saharan Africa; nearly 3 million cases occur in Southeast Asia; and over 250,000 occur in Eastern Europe. AIDS (autoimmune deficiency syndrome) with coexistent mycobacterial infection is bringing TB back into Western cities and seriously threatens health services in the developing world.
The rate of tuberculosis infection in the United States had been declining steadily until 1984 and then increased. Numerous factors account for the resurgence of tuberculosis in the United States and in Europe. They include the following:
- Emergence of multidrug-resistant strains of M. tuberculosis
- Erosion of systems for diagnosis and treatment of the disease
- Immigration of infected persons from countries where TB is prevalent
- Prevalence of HIV (human immunodeficiency virus) infection and AIDS
- Reactivation of disease in the elderly
- Socioeconomic decline in urban areas
The rapid response of state and federal agencies in the United States has averted a potentially drastic rise in TB incidence.
