Scientists surmise that migratory birds carrying H5N1 in their guts have transported the virus far from its origin in southern China as they traverse the vast aerial interstates that crisscross the globe. The eight major flyways cover nearly every speck of land on Earth -- with the exception of Antarctica -- and they all overlap.
Infected birds from China flying along the Central Asia flyway could have mixed with birds from the neighboring East Africa-West Asia flyway, bringing the virus to Kazakhstan in August. From there, it's an easy jump to the Black Sea-Mediterranean flyway, which encompasses Romania, Turkey and Croatia -- three countries where birds tested positive for H5N1 in October.
The East Asia-Australia flyway, which stretches from Australia to Siberia and over to Alaska, would be the likely culprit for bringing the virus to North America. Once in Alaska, migratory birds could pick it up and carry it south along the Pacific Americas flyway or the Mississippi Americas flyway, which encompass most of the Western Hemisphere.
There is no known way to stop it now.
Government officials thought they could contain the spread of H5N1 by culling millions of farm birds. That notion now seems quaint, as wild birds have become a permanent natural reservoir for the virus.
For The Record
Los Angeles Times Saturday January 14, 2006 Home Edition Main News Part A Page 2 National Desk 1 inches; 67 words Type of Material: Correction
Bird flu -- A front-page article Tuesday about avian influenza said 8 million Spaniards died from a virulent flu strain in May 1918. The number was based on a 1918 report in the British Medical Journal that was never substantiated. The true figure is unknown, but modern estimates place the death toll from the so-called Spanish flu that year at as many as 50 million people worldwide.
Detecting the first signs of H5N1's arrival here will give farmers and public health officials crucial time to ready their defenses, said Dr. John Clifford, chief veterinarian at the U.S. Department of Agriculture.
It is a painstaking vigil.
This summer, in the marshy land of Chevak, Runstadler and his fellow researchers corralled brant geese into a temporary pen. Then he began collecting samples from each bird's hindquarters with the gentle rub of a Dacron swab. The swabs were deposited in ethanol to preserve any virus that might be present.
The weeklong effort produced samples from more than 1,000 migratory birds. Similar efforts around the state yielded 4,000 more samples from mid-May to late September.
About 500 of the samples have been screened so far. More than 15% have tested positive for avian influenza.
So far, none of the strains are H5N1.
The birds, however, will return in the spring.
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On the move
History of influenza
412 BC - Hippocrates describes a disease that is probably influenza.
1580 - First recorded pandemic: An outbreak begins in Asia and spreads to Europe, Africa and the Americas.
1918 - H1N1 influenza: A pandemic known as the Spanish flu kills up to 50 million people worldwide.
1957 - H2N2: An Asian flu pandemic begins in China. It kills 70,000 people in the United States and up to 2 million people worldwide.
1968 - H3N2: Hong Kong flu pandemic kills 34,000 people in the United States and about 70,000 people worldwide.
1997 - H5N1: Bird flu infects 18 people in Hong Kong, killing six. The outbreak is the first known case of an avian flu being transmitted directly to people. Birds are slaughtered.
2001 - H5N1: Strains resurface in Hong Kong live poultry markets. Birds are slaughtered. There are no human cases.
2003 - H5N1: The virus begins spreading throughout Asia, causing at least one death in Hong Kong.
2004 - H5N1: Human infections reported in Vietnam and Thailand.
2005 - H5N1: Human infections also reported in Indonesia, Cambodia and China.
2006 - H5N1: Turkey reports first human cases outside of Asia.
Sources: American Scientist, Institute of Medicine, Lancet, U.S. Centers for Disease Control and Prevention, Wetlands International, World Health Organization
Graphics reporting by Rosie Mestel, Tom Reinken and Karen Kaplan