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The strain of avian influenza virus that has led to the deaths of 140 million birds and 60 people in Asia in the past two years appears to be slowly acquiring genetic Changes typical of the "Spanish flu" virus that killed 50 million people nearly a century ago, researchers said yesterday.
How far the "bird flu" virus has traveled down the evolutionary path to becoming a pandemic virus is unknown. Nor is it certain that the much-feared strain, designated as influenza A/H5N1, will ever acquire all the genetic features necessary for rapid, worldwide spread.
Nevertheless, the similarities between the Spanish flu virus of 1918 and the H5N1 strain slowly spreading through Asia provide unusually concrete evidence of how dangerous the newer virus is. At least four of its eight genes now contain mutations seen in the deadly strain that circled the globe during and after World War Ⅰ.
The comparison of the old and new flu viruses is the first practical use of a science use of a science-fiction-like scenario that concluded yesterday with the release of two papers, one by the journal, Science and the other by its chief competitor, Nature.
After 10 years of work, Taubenberger and his team succeeded in reconstructing the Spanish flu virus, which was responsible for the deadliest epidemic since the Black Death of the Middle Ages. Reborn in the mid-August at a high-security laboratory at the Centers for Disease Control and Prevention in Atlanta, the pathogen(病原体) appears in animal experiments to be as lethal as it was in human 87 years ago.
The report came as the United States, many other countries and the World Health Organization are making increasingly urgent preparations for a new flu pandemic. The Department of Health and Human Services is stockpiling antiviral drugs and is buying enough experimental bird flu vaccine to inoculate 20 million people. President Bush (the former President of America) said in a news conference this week that he is considering the use of the military to enforce quarantines, if necessary, and that the government’s long-awaited pandemic plan will be released soon.
What makes the accomplishment reported yesterday so remarkable is that no intact samples of the Spanish flu virus exist. When the pandemic occurred in 1918 and early 1919—only American Samoa and parts of Iceland appear to have been spared—microbiologists did not know for certain what caused it (The influenza virus was not identified until 1933). Although biologists were later able to deduce the broad family of influenza viruses the 1918 strain came from, its genetic identity was lost.