SCIENCE IN THE NEWS - Successes Against Tuberculosis, But No（在线收听）

SCIENCE IN THE NEWS - Successes Against Tuberculosis, But Not Everywhere
By George Grow

Broadcast: Tuesday, July 19, 2005

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VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty.

VOICE TWO:

And I'm Barbara Klein. On our program this week, we tell about the disease tuberculosis. Tuberculosis can be deadly if not treated the right way. It is a serous health problem around the world.

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VOICE ONE:

The World Health Organization says one-third of the world's population is infected with the TB bacteria. Between five and ten percent of those infected become sick with tuberculosis at some time during their life. Almost nine million people become sick with the disease each year. More than one million seven hundred thousand people die of the disease each year.

In March, the W.H.O. reported that the war against TB is being successfully fought in many areas. It said the number of TB cases worldwide has dropped twenty percent since nineteen ninety. It also said infection rates are now falling or unchanged in five of six areas around the world.

The exception is Africa. The W.H.O. said TB rates in Africa are still rising at a rate of three to four percent each year. TB rates there have risen two hundred percent since nineteen ninety in areas where many people have the virus that causes AIDS.

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VOICE TWO:

Tuberculosis is a bacterial infection that usually attacks the lungs. Most people infected with the bacteria never develop active TB. However, people with weak body defense systems often develop the disease. TB can damage a person's lungs or other parts of the body and cause serious sickness.

The disease is spread by people who have active, untreated TB bacteria in their throat or lungs. The bacteria are spread into the air when people with the disease talk, cough or sneeze or expel air suddenly.

People who breathe infected air from a TB victim can become infected with the tuberculosis bacteria. However, most people with active tuberculosis do not expel very many TB bacteria.

So, the spread of the disease usually does not happen unless a person spends a great deal of time with a TB victim. Those most at risk are family members, friends and people who work closely with a TB victim. If a person becomes infected with the TB bacteria, it does not mean he or she has the disease. Having the infection means that the bacteria are in the body, but they may be neutral, or inactive.

VOICE ONE:

After the TB bacteria enter the body, the body's defense system against disease usually acts to surround the bacteria and prevent them from spreading. The immune system does this by building a wall around the bacteria similar to the way blood hardens around a cut on the skin. The bacteria can stay alive in an inactive condition inside these walls for many years.

When TB bacteria are inactive, they cannot damage the body. And they cannot spread to other people. People with the inactive bacteria are infected, but they are not sick. They probably do not know that they are infected. Millions of people have the TB infection. For most of them, the bacteria will always be inactive. They will never suffer signs of tuberculosis.

VOICE TWO:

 
 
If the body's immune system is weak, however, a person can get tuberculosis soon after the TB bacteria enter the body. Also, inactive TB bacteria may become active if the immune system becomes weak. When this happens, the bacteria can break through the protective walls. Then, they begin reproducing and damaging the lungs or other organs. When TB bacteria become active, they can cause serious sickness.

The inactive TB bacteria can become active under several conditions. When a person becomes old, the immune system may become too weak to protect against the bacteria. A serious sickness can weaken the immune system enough to free the TB bacteria. H.I.V., the virus that causes AIDS, can cause TB bacteria to become active. Also, doctors warn that people who drink too much alcohol or use illegal drugs have a higher risk of becoming sick from the tuberculosis bacteria.

VOICE ONE:

TB can attack any part of the body. However, the lungs are the most common targets of the bacteria. People with the disease show several signs. They expel air from the lungs suddenly with an explosive noise, or cough. This cough continues for a long period of time. People with a more severe case of tuberculosis also may cough up blood.

People with the disease often have high body temperatures. They suffer what are called night sweats, during which their bodies give off large amounts of water through the skin. TB victims also are tired all the time. They are not interested in eating. So they lose weight.

One thing that is especially dangerous about TB is that people with moderate signs of the disease may not know they have it. They may spread the disease to others without even knowing it. So, it is very important for people to get tested for tuberculosis.

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VOICE TWO:

There are several ways to test for TB. The first is the TB skin test. It also is known as the Mantoux (MAN-two) skin test. The test can identify most people infected with tuberculosis six to eight weeks after the bacteria entered their bodies. A substance called purified protein derivative is injected under the skin of the arm. The place of the injection is examined two to three days later.

If a raised red area forms, the person may have been infected with the tuberculosis bacteria. However, this does not always mean the disease is active.

VOICE ONE:

If the skin test shows that TB bacteria have entered the body, doctors can use other methods to discover if the person has active T-B. However, this sometimes can be difficult because tuberculosis may appear similar to other diseases. Doctors must consider other physical signs. Also, they must decide if a person's history shows that he or she has been in situations where tuberculosis was present.

Doctors also use an X-ray examination to show if there is evidence of TB infection, such as damage to the lungs. Another way to test for the presence of active tuberculosis is to examine the fluids from a person's body, especially those taken from the mouth.

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VOICE TWO:

It is very important for doctors to identify which kind of TB bacteria are present so they can decide which drugs to use to treat the disease. More than ninety percent of TB cases can be cured with medicines. However, the death rate for untreated patients is reported to be about fifty percent. Successful treatment of TB requires close cooperation among patients, doctors and other health care workers.

It is very important for patients to be educated about the disease and its treatment. Patients must take medicine for six to twelve months to destroy all signs of the bacteria. Sometimes patients fail to finish taking the medicine ordered by their doctors. Experts say this is because some patients feel better after only two to four weeks of treatment and stop taking their medicine.

This can lead to the TB bacteria becoming resistant to drugs and growing stronger, more dangerous and more difficult to treat. Because of this, many doctors and other health care workers directly observe and supervise treatment of the disease in their patients.

VOICE ONE:

Experts say TB is a preventable disease. In the United States, the goal of health organizations is to quickly identify infected people – especially those who have the highest risk of developing the disease. There are several drugs that can prevent tuberculosis in people who are at risk of becoming infected. These people include those who live or work closely with people who have TB. Others at risk are people who are infected with tuberculosis bacteria but do not have the active disease.

VOICE TWO:

There are a number of ways to limit the spread of tuberculosis. All TB patients must learn to cover their mouths and noses when they cough or sneeze. It also is important to keep air flowing through rooms so that the TB bacteria cannot gather and infect people. Also, ultraviolet light and other devices can be used to clean infectious bacteria from the air in closed rooms.

Experts say tuberculosis can be cured if it is discovered early and if patients take their medicine correctly. And, like other diseases, education and understanding are extremely important in preventing and treating TB.

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VOICE ONE:

This SCIENCE IN THE NEWS program was written by George Grow. Cynthia Kirk was our producer. I'm Bob Doughty.

VOICE TWO:

And I'm Barbara Klein. Join us again next week for more news about science in Special English on the Voice of America.