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This is SCIENCE IN THE NEWS in VOA Special English. I’m Pat Bodnar.

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And I’m Bob Doughty. This week on our show: A scientist says eating less fish during pregnancy may do more harm than good ...

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Studies say two new vaccines against rotavirus are safe and effective for young children ...

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And explaining the ancient Plague of Athens.

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Two years ago, the United States government advised pregnant women to limit fish in their diet to three hundred forty grams a week. Women in some other countries get the same advice. The aim is to reduce the risk that mercury pollution in fish could harm the developing nervous system in children.

But now an American government researcher says women who follow this advice may be harming their children instead of protecting them. Joseph Hibbeln [pronounced HIH-beh-lin] is a medical doctor who works at the National Institutes of Health. He says the value to brain development from the omega-three fatty acids in fish oil outweighs the risk from mercury.

'My belly is not a chemical location' is the message of these pregnant women in Germany, protesting against industrial pollution. Yet a researcher suggests that the risk to fetuses from mercury in fish may be overstated.

On January seventeenth he spoke at a scientific meeting in London to report the findings of new research.

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Doctor Hibbeln and British scientists used information about thousands of British children. The information came from a health study known as the Children of the Nineties project, based at the University of Bristol. The research led by Doctor Hibbeln looked at the records of nine thousand pregnant women. The information included the amount of seafood their mothers ate while pregnant.

The researchers compared families that ate plenty of fish against those that ate less than three hundred forty grams per week. They also compared the development of the children at different ages.

They found important differences between the children of women who ate a lot of fish and the children of women who did not. The scientists based their observations on thirty-one different tests.

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These are some of the reported findings:

By around two years old, children whose mothers ate no fish had lower scores in tests for motor, communication and social skills. At the age of seven, they had more problems dealing with other children. And by eight they were more likely to do poorly on intelligence tests of language skills.

Mothers who had the most omega-three fatty acids in their diet had the children with the best fine-motor skills at age three-and-a-half.

Doctor Hibbeln has called some of the findings "frightening."

He says those responsible for the health advisory looked only at a study of the effects of eating whale meat with high mercury levels. He says they did not consider the risk of restricting the nutrients that pregnant women can get from fish.

Doctor Hibbeln would not comment further on the study until the findings appear in a scientific publication. First, other scientists must read and approve the report. But he tells us that the Medical Research Council of Britain, the Wellcome Trust and the National Institutes of Health paid for the research.

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Nearly all fish contains some amount of mercury. Some kinds contain more than others. Mercury is a metallic element. It gets into the environment from the burning of coal and other fossil fuels. It also comes from the use of mercury in electronics and other products.

The advisory in two thousand four came jointly from the Food and Drug Administration and the Environmental Protection Agency. They said eating seafood is not a health concern for most people. But they had advice for young children and three groups of women. These are pregnant women, women who might become pregnant and those who breastfeed their babies.

The women and children were advised not to eat shark, swordfish, king mackerel or tilefish because they contain high levels of mercury.

The agencies said five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock and catfish. Albacore or "white" tuna has more mercury than canned light tuna.

The women and children were also told to be very careful about the safety of fish caught in local waterways.

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Omega-three fatty acids have been in the news for years. Research has shown that some may reduce the risk of heart attacks by reducing the risk of blockages in the blood system. Also, Doctor Hibbeln says countries with the highest rates of eating fish have lower rates of depression, and even lower rates of murder.

Walnuts and seed oils also contain omega-threes. But many researchers say fish oil, or fish oil supplements, are the best way to get them.

There may be limits to the power of fish oil, though. Scientists have just reported that it does not appear to reduce the risk of cancer.

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

More than two thousand four hundred years ago, a sickness struck Athens. The disease is said to have killed up to one third of all Athenians, including their leader Pericles. The huge loss of life helped to change the balance of power between Athens and its enemy, Sparta, in the ancient world.

Historians say the sickness began in what is now Ethiopia. They say it passed through Egypt and Libya before it entered Greece. Knowledge of the disease has come mainly from the writings of the ancient Greek historian Thucydides, who survived it.

So what caused the fall of Athens? Among the diseases that have been suggested are anthrax, bubonic plague, measles and smallpox. Now, a study based on genetic testing says it was probably typhoid fever.

Greek researchers announced the results. The International Journal of Infectious Diseases published the findings online last week.

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Researchers from the University of Athens tested human remains from an ancient burial place in the Greek capital. The researchers collected genetic material from teeth. They say tests found genetic evidence similar to that of the modern-day organism Salmonella enterica serovar Typhi.

Manolis Papagrigorakis led the University of Athens team. He says the findings throw light on one of the most debated mysteries in medical history.

Typhoid fever is a life-threatening disease that is common today in developing countries. Experts say there are more than twenty-one million cases each year.

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Typhoid can be spread by food or drink that has been handled by a person infected with the bacteria that causes it. Bacteria expelled in human waste can pollute water supplies. So water used for drinking or to wash food can also spread the infection.

Hand washing is important to reducing the spread of typhoid. And there are vaccines that can help prevent it.

People with typhoid fever usually develop a body temperature as high as forty degrees Celsius. But experts at the Centers for Disease Control and Prevention in the United States say typhoid can usually be treated with antibiotics.

Some people recover but continue to carry the bacteria. These carriers can get sick again. And they may continue to infect others. Doctors can do tests to make sure the bacteria has left the body.

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Another disease that is common in developing countries is rotavirus. Babies and young children around the world are affected by this intestinal condition. Yet rotavirus is a leading killer of young children in the developing world. The severe diarrhea it causes can be deadly unless treated. Most of the estimated half-million deaths each year are in poor countries.

But major studies show that two new vaccines are safe and effective in preventing most cases of severe rotavirus in young children. The drug company GlaxoSmithKline makes one of the vaccines, called Rotarix. Merck makes the other one, called RotaTeq.

The New England Journal of Medicine published the studies, which were supported by the makers. Rotarix is already sold in some countries. RotaTeq is not yet for sale.

In nineteen ninety-nine, the drug company Wyeth removed a rotavirus vaccine from the American market. That drug was blamed for some cases of an intestinal blockage. The studies of Rotarix and RotaTeq, however, say the two new vaccines did not show any increase in risk for that condition.

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SCIENCE IN THE NEWS was written by George Grow and Jill Moss. Cynthia Kirk was our producer. I'm Bob Doughty.

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And I’m Pat Bodnar. Internet users can read and listen to our programs at voaspecialenglish.com. Join us again next week for more news about science in Special English on the Voice of America.