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    Killer Bird Flu Fuels Plague Fears

    New Worldwide Flu May Be Brewing in Asia

    What Happened Last Time

    Here's why the experts worry. The part of the flu bug that determines immunity is the H (for hemagglutinin) molecule on the outside of the virus. There are 15 different H molecules in birds. But people get only three kinds: H1, H2, and H3.

    Type A flu is a wily bug. It likes to shift its genes around. That happened this year, when the H3 Panama flu morphed into the H3 Fujian flu. But that difference -- called a drift -- isn't as bad as when the flu bug "shifts." That happens when it picks up a new H gene from an animal flu virus.

    Once upon a time, people didn't get much influenza type A. Then the bug learned to pick up genes that let it spread from human to human. It's happened three times:

    • "Spanish flu" -- H1 -- broke out in 1918-1919. It killed 500,000 people in the U.S. and as many as 50 million people worldwide.
    • "Asian flu" -- H2 -- broke out in 1957-1958. It killed 70,000 Americans.
    • "Hong Kong flu" -- H3 -- broke out in 1968-1969. It caused 34,000 U.S. deaths. This strain is still around. This year's "Fujian flu" is an H3 variant.

    The bird flu sweeping Asia is an H5 flu bug. It's tried to break out before. In 1997 it broke out in Hong Kong. Eighteen people got infected; six died. Authorities ordered the extermination of all the chickens in Hong Kong. This mass slaughter ended the threat.

    An H9 bird flu infected two Hong Kong children in 1999. Both recovered fully. Other H9 infections were reported in China, but this bug hasn't broken out.

    Last year, an H7 bird flu infected chicken handlers in the Netherlands. One veterinarian died. Authorities called for the slaughter of infected birds. And health authorities gave human flu vaccines to all poultry handlers in an effort to prevent dual infection that might lead to a new human flu.

    What's Happened This Year -- so Far

    Likely carried by wild ducks and/or geese, an H5 bird flu swept through South Korea and turned up in Vietnam and Japan. Other nations deny a problem, although last December both Japan and Taiwan reported finding H5 flu in ducks illegally smuggled out of China.

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