SCIENCE IN THE NEWS - Polio: How an Ancient Disease Met a Mo（在线收听）

SCIENCE IN THE NEWS - Polio: How an Ancient Disease Met a Modern Prevention
By Jerilyn Watson

Broadcast: Tuesday, April 26, 2005

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VOICE ONE:

This is SCIENCE IN THE NEWS, in VOA Special English. I'm Faith Lapidus.

VOICE TWO:

 
Dr. Jonas Salk(Photo - Yousuf Karsh 1956/National Gallery of Australia)
And I'm Bob Doughty. This week, we remember the discovery of the first effective protection against the disease polio. We also talk about the scientists who made it possible.

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VOICE ONE:

Fifty years ago, American media reported a major and welcome announcement. They said scientists had created a medicine to protect people against polio. The medicine was described as safe, powerful and effective. The announcement was made on April twelfth, nineteen fifty-five. The date is now fixed in medical history.

Today, international efforts have greatly reduced cases of polio around the world. The World Health Organization supports a campaign to end the health threat from the disease by this year. A worldwide effort called the Global Polio Eradication Initiative is working toward this goal.

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About three hundred fifty thousand polio cases were reported in one hundred twenty-five countries in nineteen eighty-eight. Since then, the number of cases has been cut by ninety-nine percent.

But some nations have not stopped the spread of the disease. The W-H-O says heavily populated countries like India and Nigeria still report cases. Polio remains a problem in other countries like Afghanistan, Egypt, Niger and Pakistan.

Doctors say most patients suffer only signs of a cold or mild intestinal problem. Yet polio has been one of the most frightening diseases in history. People with the most severe cases died, sometimes quickly. Others were left unable to walk or breathe on their own. There was no cure or truly effective treatment.

In recent years, some people who were infected long ago have developed new pain and weakness. The problem is called post-polio syndrome.

VOICE ONE:

Polio was first recorded in ancient Egypt, Greece and Rome. A virus causes the disease. It attacks the muscles and nervous system. The sickness spreads from person to person. It is carried in food, water and human waste.

Scientists first identified the virus in nineteen oh-eight. But they could not stop the sickness from spreading. For example, polio killed six thousand people in the United States in nineteen sixteen. Twenty-seven thousand other Americans suffered permanent damage.

For years, polio remained a health threat. Many victims were children and young adults. Families attempted all kinds of methods to protect their children. But still the sickness kept spreading. This was especially true during hot summers. In the summer of nineteen fifty-two, more than fifty-seven thousand Americans were infected.

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Antibiotic medicines do not destroy viruses. Only bacteria can be killed that way. Medicines that kill viruses also kill healthy cells. That is why it was necessary for scientists to prevent a viral infection instead of attempting to treat it.

Only three vaccines were used for viral sicknesses until the nineteen forties. A vaccine works by placing a small amount of weakened virus in the body. This helped the body develop substances in the blood that can destroy the disease if it appears. These substances are called antibodies.

VOICE ONE:

Several research scientists were working to develop a treatment for polio after World War Two. But Jonas Salk wanted to create a protective medicine. He believed a vaccine made from a killed virus could kill the polio virus. However, other researchers said his method would never succeed.

Doctor Salk did not listen. He gathered a team of experts at the University of Pittsburgh School of Medicine in the state of Pennsylvania. They worked to produce a substance that could kill a live poliovirus.

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Millions of Americans provided money for the research. Adults and children would give their money to the Infantile Paralysis Foundation. Today, the group is called the March of Dimes.

President Franklin Delano Roosevelt helped start the Foundation in the late nineteen thirties. Mister Roosevelt became sick with polio when he was thirty-nine years old. He never walked again without help.

The money from Americans helped Doctor Salk's team create antibodies that would kill the virus. In nineteen fifty-two, the team identified three major kinds of polio virus. That meant creating a vaccine that would kill all three. The team also had to discover how to grow the viruses.

VOICE ONE:

In the nineteen thirties, scientists used tissue from the backbones of monkeys to grow the virus. The tissue was called neural tissue. However, vaccines with the virus grown in neural tissue gave people the disease.

A young man named Julius Youngner worked with Doctor Salk to develop a way to grow the virus in non-neural tissue. Professor Youngner decided to use tissue from the kidneys of monkeys.

He did so by cutting up the outer cover of this organ. At first, it was hard for him to grow the cells. They became thick in test tubes. But then he added a substance called trypsin. The trypsin made the tissue break into separate cells.

Julius Youngner developed ways to grow enough of the virus needed to produce a vaccine. Other scientists say he invented modern cell cultures. But Professor Youngner says the real heroes were the monkeys. Today, he is the only survivor of Doctor Salk's main research team.

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VOICE TWO:

Other researchers did not agree that the killed virus made the most effective vaccine. One of them was Albert Sabin. He disagreed with the way Doctor Salk's team was building antibodies to fight polio. Doctor Sabin wanted to use a weakened live polio virus to build disease antibodies.

Doctor Sabin attempted to prevent the test of the Salk polio vaccine. But the attempt failed. A large trial of the Salk vaccine began in nineteen fifty-four. The results showed that polio rates decreased greatly in people who had been vaccinated. The next April, the medicine was declared safe and effective.

VOICE ONE:

The Salk polio vaccine was given with a needle, through the skin. Americans often call such an injection a shot. American parents hurried to get their children protected. Hundreds of thousands of Europeans also got shots. That caused people to say that the Salk vaccine was the shot felt 'round the world.

Now it was time for Doctor Sabin to gain fame in the struggle against polio. In nineteen fifty-seven, he developed a vaccine containing live poliovirus. People could take his oral polio vaccine by mouth. It was easier to protect great numbers of people with the Sabin vaccine than with the Salk vaccine.

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One hundred million children in Europe received the Sabin oral polio vaccine in nineteen-sixty. His vaccine was given to one hundred million Americans of all ages from nineteen sixty-two through nineteen sixty-four.

Today, the United States Department of Health and Human Services no longer advises the oral polio vaccine. Instead, officials strongly advise that shots be given to babies and young children. Most adult Americans do not need the vaccine.

This month, the Smithsonian Institution in Washington, D.C., has organized a show called "Whatever Happened to Polio?" The name offers evidence that the disease is rare in much of the world.

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Yet polio keeps returning. For example, it disappeared in the western half of the world by the end of the twentieth century. Then, in two thousand one, tests confirmed that several children in the Dominican Republic and Haiti had become infected.

Strong danger from polio still exists in parts of Africa. This month, a coalition of health agencies is working to protect millions of children there. Earlier in the year, United Nations agencies and the Global Polio Eradication Initiative reached up to ninety five million children with the polio vaccine.

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An American doctor remembers seeing many children infected with polio at a hospital during the nineteen fifties. Their whole bodies except their heads were inside tanks called iron lungs. The devices helped them to breathe. Some never left the iron lungs.

In the words of the doctor, controlling polio is more than worth the effort.

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VOICE ONE:

This program was written by Jerilyn Watson. Our producer was Cynthia Kirk. I'm Faith Lapidus.

VOICE TWO:

And I'm Bob Doughty. Join us again next week for SCIENCE IN THE NEWS in VOA Special English.