Asia is world's cradle for new flu strains

Last update: April 16, 2008 - 8:39 PM

Scientists have pinpointed the cradle-to-grave path that flu takes as it sweeps the globe every year -- starting with the birth of new strains in Asia and ending when the virus burns out in South America.

In between, influenza catches a ride to North America and Europe about six to nine months after a new strain emerges in Asia, a pattern that promises to help health authorities better prepare each winter's flu vaccine.

Already, monitoring is being beefed up in parts of East and Southeast Asia "as fast as we can" in hopes of more accurately spotting strains poised to jump continents, said Dr. Michael Shaw, a flu specialist with the U.S. Centers for Disease Control and Prevention.

Now, "we know the part of the world to look in, and the probable time of the year to look," he said.

The good news: Once they leave Asia, new flu strains don't seem to get more dangerous as they migrate from continent to continent, an international research team reports in Friday's edition of the journal Science.

"Once the viruses leave that region, they're really on a pathway to an evolutionary graveyard," said Derek Smith of Britain's University of Cambridge, who helped lead the team.

Why those routes? Travel and trade, says study lead author Colin Russell of the University of Cambridge: There is far less direct air travel between Asia and South America than Asia and North America, for example. By the time the virus made it to South America, the rest of the planet already had been exposed.

FACTORS THAT GUIDE PREEMIE SURVIVAL

Doctors now have a better way of helping parents make an agonizing decision -- whether to take heroic steps to save a very premature baby.

The number of weeks in the womb has generally been the chief factor. But a new study shows others are important, too -- including whether the fetus is a girl and whether the fetus gets lung-maturing steroids shortly before birth. Those extra factors can count as much as an extra week of pregnancy.

The new method uses an online calculator developed specifically for such cases. It factors in birth weight, sex and generates statistics on chances of the baby's survival and the likelihood it will have disabilities (www.nichd.nih.gov/neonatalestimates).

The new information could change how doctors and parents decide what kind of care to provide to tiny, fragile premature infants, said John Langer, a co-author of the study being published this week in the New England Journal of Medicine.

Besides being a girl and getting the steroids, an extra 3 1/2 ounces or so of weight and being a single birth also helped as much as an extra week of pregnancy, the study found. The research focused on extremely premature babies, those born after 22 to 25 weeks in the womb. A full term is about 40 weeks.

aP, new york times

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