VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Barbara Klein.

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And I'm Steve Ember. 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:

Tuberculosis is one of the leading infectious diseases. The World Health Organization says two billion people are infected with the TB bacteria. That is about one-third of the world's total population.

One in ten people infected with the TB bacteria will become sick with tuberculosis at some time during their life. Almost nine million people become sick with the disease each year. About one million six hundred thousand people will die of the disease this year.

The World Health Organization says TB is a disease of poverty. It affects mostly young adults in their most productive years. The large majority of deaths from the disease are in developing countries. More than half of all deaths happen in Asia.

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The World Health Organization declared TB a public health emergency in nineteen ninety-three. A new WHO report shows tuberculosis rates around the world are falling or unchanged. The report says rates were unchanged in two thousand five after reaching record high levels one year earlier.

If this continues for the next three or four years, WHO officials believe their Millennium Development Goal could be reached. The goal is to discover at least seventy percent of TB cases and successfully treat eighty-five percent of those cases by the year two thousand fifteen.

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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 health problems.

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 or expel air suddenly.

VOICE TWO:

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 large amount of time with a TB patient. Those most at risk are family members, friends and people who live or work closely with a patient.

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:

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. For most of them, the bacteria will always be inactive. They will never suffer signs of tuberculosis.

If the natural immune system against disease 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 begin reproducing and damaging the lungs or other organs and causing 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. The virus that causes AIDS can cause TB bacteria to become active. Also, doctors warn that people who drink too much alcohol or use drugs have a higher risk of becoming sick from the tuberculosis bacteria.

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VOICE TWO:

Tuberculosis 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 may expel air from the lungs suddenly with an explosive noise. This kind of 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 release large amounts of water through the skin. TB victims also are tired all the time. They are not interested in eating. So their bodies 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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There are several ways to test for TB. The first is the TB skin test. It also is known as the Mantoux 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 TWO:

If the skin test shows that TB bacteria have entered the body, doctors can use other methods to discover if the person has active TB. 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 mouth.

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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. Most TB cases can be successfully treated 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.

The World Health Organization has a five-step program to guarantee that TB patients take their medicine correctly. The program is called Directly Observed Treatment, Short-course, or DOTS. Directly observed means that local health care workers watch to make sure patients take their medicine every day. Full treatment usually lasts from six to nine months to destroy all signs of the bacteria.

It is very important for patients to be educated about the disease and its treatment. 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.

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Experts say TB is a preventable disease. The goal of health organizations is to quickly identify infected persons – especially those who have the highest risk of developing the disease. There are several drugs that can prevent tuberculosis in these people.

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. Next week, we will tell you about efforts to fight TB in several countries.

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VOICE ONE:

This SCIENCE IN THE NEWS was written by George Grow and Shelley Gollust. Brianna Blake was our producer. I'm Barbara Klein.

VOICE TWO:

And I'm Steve Ember. We would like to hear from you. Write to us at Special English, Voice of America, Washington, DC, two-zero-two-three-seven, USA. Or send electronic messages to special@voanews.com. Join us again next week for more news about science in Special English on the Voice of America.