Tuberculosis (TB) is a chronic bacterial infection caused by
Mycobacterium tuberculosis. It is spread through the air and usually infects the lungs, although other organs and parts of the body can be involved as well. Most people who are infected harbor the tuberculosis bacterium without symptoms. This is known as
latent tuberculosis.
If the body's resistance is low because of aging, malnutrition, infections such as
HIV, or other reasons, the bacteria may break out of hiding and cause
active tuberculosis.
According to World Health Organization (WHO) estimates, each year, eight million people worldwide develop active tuberculosis and nearly two million die. One in 10 people who are infected with tuberculosis may develop active TB at some time in their lives. The risk of developing the active disease is greatest in the first year after infection, but active disease often does not occur until many years later.
The cause of the disease is a bacterium called Mycobacterium tuberculosis. This bacterium usually attacks the lungs. However, TB bacteria can also attack any part of the body such as the kidneys, spine, and brain. If not treated properly, TB can be fatal.
Tuberculosis is spread through the air from one person to another. The bacteria are put into the air when a person with active TB of the lungs or throat coughs or sneezes. People nearby may breathe in these bacteria and become infected.
People cannot get infected with TB through handshakes, sitting on toilet seats, or sharing dishes and utensils with someone who has TB.
In most people who breathe in the bacteria and become infected, the body is able to fight the bacteria to stop them from growing. The bacteria become inactive, but they remain alive in the body and can become active later. This is called
latent tuberculosis. People with this form of the disease:
- Have no symptoms of tuberculosis
- Don't feel sick
- Can't spread TB to others
- Usually have a positive TB skin test (PPD test) reaction.
Some people with the latent form of the disease can develop active
tuberculosis disease if they do not receive treatment.
If the body's resistance is low because of aging, malnutrition, infections such as
HIV, or other reasons, the bacteria may break out of hiding and cause
active tuberculosis.
In these cases, symptoms can include:
- Unexplained weight loss
- Fever
- Chills
- Night sweats
- Weakness or fatigue
- Loss of appetite
- Cough that lasts 3 weeks or longer
- Pain in the chest
- Coughing up blood or sputum.
Specific tests will help the doctor make the diagnosis and determine whether it is the disease is active or latent
(see Latent Versus Active Tuberculosis). These TB tests can include a TB skin test (PPD test), TB blood test, and other tests, such as a chest x-ray and samples of sputum.
Treatment involves taking several different antibiotics for at least six months (and in some cases, up to several years). In most cases, by taking medication, the tuberculosis can be cured.
A
tuberculosis cure relies on close cooperation between the patient and doctor or other health care workers in order to make sure that the right amount of medicine is taken for the right amount of time. If less than the right amount of medicine is taken, or if it is taken for a shorter period of time, a tuberculosis cure is less likely. Furthermore, there is a greater chance a person will develop
drug-resistant TB, a condition that is more difficult to cure.
Tuberculosis is largely a preventable disease. Prevention focuses on:
In 2005, the Centers for Disease Control and Prevention (CDC) reported 14,093 cases of
active tuberculosis (TB) in the United States. In addition to those with active tuberculosis, an estimated 10 to 15 million people in the United States have latent tuberculosis. On average, about 10 percent of these infected individuals will develop active tuberculosis at some point in their lives. Some underlying conditions increase the risk that latent TB infection will progress to active
tuberculosis disease -- the risk can be 3 times higher (as with
diabetes) to more than 100 times higher (as with
HIV infection).
It is believed that tuberculosis has been infecting humans for thousands of years.
Bone remnants dating back to 4000 BC show evidence of tuberculosis.
A
tuberculosis cure was developed (through the testing of streptomycin) more than 50 years ago.
TB continues to kill between two and three million people every year. The World Health Organization (WHO) estimates that 36 million people will die of tuberculosis by 2020 if it is not controlled.
