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

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And I'm Barbara Klein.Our subject this week is bird flu.

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There are many kinds of avian influenza.The one that has many people concerned is caused by the virus h-five-n-one.This virus has killed birds in about forty countries.It is highly deadly to chickens, turkeys and other poultry.But birds are not the only ones at risk.

The first known cases in humans appeared in nineteen ninety-seven in Hong Kong.Since two thousand three, the virus has been found in more than one hundred eighty people in at least eight countries.More than one hundred of them have died.

So far, experts say most of the victims have been infected directly from sick birds.But there is concern that the virus could change into a form that spreads easily from one person to another.

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Infections have been found in sixty kinds of wild birds.The part that migratory birds play in spreading the virus is still being studied.Experts still do not know exactly how the virus spread from Asia to Europe and Africa.

Migratory birds fly long distances between a winter home and a summer home.Some researchers say these birds are getting too much blame.But American scientist Robert Webster believes ducks are a big part of the problem.He says ducks might not get sick from bird flu but spread the disease easily to chickens.

Some experts think the virus could reach the United States in April or May.They say it could arrive when ducks and other wild birds from Asia reach Alaska.Government scientists are testing thousands of wild birds flying across the state.

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Animal health experts say people who want to protect chickens and other birds should keep them in closed areas, away from wild birds.Also, farm birds should not drink from water used by wild birds.

If the virus appears, people with special training and protective clothing should kill all the birds on the farm.The farm must be cleaned completely.

To help prevent an outbreak, people should clean their hands and shoes before and after they visit farms or markets where birds are kept.Washing clothes and equipment after contact with birds is also important.

Any equipment or supplies that are shared with people who keep birds should be cleaned after use.Experts say items made of materials like wood and fiber should not be shared because they are more difficult to disinfect.

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In many places, chickens are kept close to or inside people's homes.This can be an infection risk, especially when children play with them.

People should cover their face and hands when they work with farm birds or wild birds.Facial protection will reduce the risk of breathing dust that might carry the infection.To increase the protection, people should not eat, drink or smoke while working with birds.

Birds that get the virus often die within forty-eight hours.Other possible signs are lack of egg production, or eggs with soft shells; lack of energy; swelling in the eyes and neck; and a purple color around the legs.

Any suspected cases should be reported to animal health officials immediately.

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VOICE ONE:

You are listening to SCIENCE IN THE NEWS in VOA Special English.

In France, the h-five-n-one virus was found in a wild duck about one kilometer from the farm of a man named Daniel Clair.Soon his chickens also had the virus.But he did not believe the duck was responsible.

Mister Clair blamed reporters.He said they brought the virus to his farm on their shoes after they went to where the dead duck was found.

The infection can spread on shoes, tires, farm equipment, clothes and people's hands.And it can spread whenever birds are transported, either legally or illegally.Illegal trade is a concern because it can sabotage efforts to stop an outbreak.

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Products made with bird waste are another concern.Bird waste is often used to make fertilizer.It is also used as food in fish farming.But untreated waste can spread the infection.In some cases wild birds are believed to have been infected by drinking water in fish farms.Experts say the virus can live in water for three weeks.

The World Health Organization says the virus can be killed in poultry products at a heat of seventy degrees Celsius.The W.H.O. also has other rules for food safety: Wash your hands before eating.Disinfect all equipment and surfaces that are used to prepare food.And do not place uncooked meat next to cooked meat.

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There are no warnings to avoid countries with cases of bird flu.But officials do advise travelers not to visit bird farms or have other contact with birds before or during their travels.

Public health officials are trying to prevent a human pandemic.A pandemic is a worldwide outbreak of disease.Pandemics happen when people have no resistance to an aggressive new virus.

Flu pandemics happen from time to time.The worst known was the nineteen eighteen Spanish flu.Many researchers estimate the dead at between twenty million and fifty million.Some say the number could be as high as one hundred million.

Many scientists say the next flu pandemic is likely to be caused by the h-five-n-one virus.Others point out that there is no way to know.

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Influenza viruses continually change.Scientists have to make new vaccines each year to protect people.It takes six months or more to develop a new flu vaccine.And even in a normal flu season it takes time to produce enough to meet demand.

Scientists are now working on vaccines to protect people against a possible bird flu pandemic.There is no cure for bird flu, just like other kinds of influenza.Two anti-viral drugs, Tamiflu and Relenza, might help reduce the severity in some cases if taken very soon after a person gets sick.

But, sooner or later, medicines can lose their effectiveness as viruses and bacteria develop resistance.So doctors are being urged to limit the use of Tamiflu and Relenza now in case they are needed for a pandemic.

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The World Health Organization is telling all countries to have a plan in case of a pandemic.A good plan must include information about finding enough hospital space for sick people.There must be information about when to close schools or workplaces.And information about when to require people to stay home, and how to get medicine.

But officials say only about forty countries have a plan.

The United States said in January that it will provide three hundred thirty-four million dollars to help other countries deal with outbreaks.

International health officials have been meeting to work on a plan so all nations get vaccines and anti-viral medicines.About thirty countries are buying large amounts of medicine.But right now the W.H.O. says it believes most developing countries will not have enough supplies to deal with a pandemic.

Some medical experts see little chance that even the United States would have enough to prevent a pandemic within the next three years.Others, though, think people worry too much about the h-five-n-one virus.

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So why does the animal virus rarely spread from human to human?New reports in Science magazine and Nature offer an explanation.Two separate teams found that the virus is only able to enter cells deep in the lungs.

Human flu viruses attach to cells in the upper part of the breathing system.People then spread the infection from the nose and mouth when they cough and sneeze.The scientists, in the United States, Japan and the Netherlands, note that genetic changes would be needed for the h-five-n-one virus to cause a pandemic.

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Before we go, here are three sites on the Internet to learn more about avian influenza.One is the Web site of the World Health Organization: who.int.

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The second is a United States government site: pandemicflu.gov.

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And the third is our Web site, WWW.51VOA.COM.You can find a link to the latest news about bird flu.

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SCIENCE IN THE NEWS was written by Karen Leggett and produced by Cynthia Kirk.I'm Barbara Klein.

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And I'm Pat Bodnar.To send us e-mail, write to special@voanews.com.Listen next week for more news about science in Special English on the Voice of America.