Tuberculosis or TB

Tuberculosis or TB

I. Introduction Print section

Tuberculosis (TB), 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. 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.

II. Transmission and Infection Print section

TB is transmitted from person to person, usually by inhaling bacteria-carrying air droplets. When a person sick with TB coughs, sneezes, or speaks, small particles that carry two to three bacteria surrounded by a layer of moisture are released in the air. When another person inhales these particles, the bacteria may lodge in that person's lungs and multiply.

A less common route of transmission is through the skin. Pathologists and laboratory technicians who handle TB specimens may contract the disease through skin wounds. TB has also been reported in people who have received tattoos and people who have been circumcised with unsterilized instruments.

A person may become infected with TB bacteria and not develop the disease. His or her immune system may destroy the bacteria completely. In fact, only 5 to 10 percent of those infected with TB actually become sick. If a person does contract the infection, disease can develop in two stages: primary and secondary.

A. Primary TB Print section

In primary TB, a person has become infected with the TB bacteria but often is not aware of it, since this stage of the disease does not produce noticeable symptoms. Primary TB is not contagious in this early stage. Macrophages, immune cells that detect and destroy foreign matter, ingest the TB bacteria and transport the...

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...esizing additional vaccines.

Incidence of Tuberculosis, United States

Many researchers attribute the sharp increase in the early 1990s to the spread of acquired immunodeficiency syndrome (AIDS). People with AIDS have weakened immune systems and are particularly susceptible to contagious diseases such as tuberculosis. Poorly supervised treatment of tuberculosis also led to an increase in drug-resistant strains of the bacteria that cause tuberculosis, furthering the spread of the disease. Renewed emphasis on control and prevention has brought the incidence of tuberculosis to record low levels.

Tuberculosis in the Lungs

Lung tissue calcification, resulting from pulmonary tuberculosis, appears as yellow patches within the chest area of this human X ray. When airborne phlegm contaminated with the bacillus Mycobacterium tuberculosis is inhaled, nodular lesions, called tubercles, may form in the lungs and spread through the nearest lymph node.

German scientist Robert Koch at work in his laboratory. Considered the founder of modern medical bacteriology, Koch isolated the bacillus that causes tuberculosis in 1882. He won the Nobel Prize for physiology or medicine in 1905.