for National Geographic News
Solving an 86-year-old medical mystery, British scientists have determined the structure of the so-called "Spanish flu" virus that jumped from birds to humans in 1918, killing more than 20 million people worldwide.
In two separate studies, researchers from the Medical Research Council in London showed that the virus likely derived from an avian virus and retained some key characteristics of its avian precursor that caught the human immune system off-guard.
Although the discovery will probably not have an immediate impact on the current outbreak of chicken flu in Asia, the work will help scientists better understand flu viruses and their transmission from birds to humans.
The new evidence suggests that "receptor binding," the initial event in virus infection in which a foreign virus mixes with human proteins, is perhaps more important than the virulence of the virus in determining risk of transmission.
"This paper is important because of the knowledge it brings about how these viruses, which originate in birds, can jump to humans," Sir John Skehel, the Medical Research Council's lead scientist on the project, said in a prepared statement. "This allows us to track and monitor the changes in the virus for public health purposes, even though it does not allow us to predict or prevent future forms of flu."
The research is published in tomorrow's issue of the journal Science.
High Mortality Rates
The influenza pandemic in 1918 was named "Spanish flu" because it was first widely reported in Spanish newspapers. News reports of the outbreak were suppressed by wartime censorship in many countries fighting in World War I.
The pandemic was exceptional in both breadth and depth. Unlike most subsequent influenza strains, which first appeared in Asia, the initial wave of the Spanish flu seemingly arose in the United States. In September through November of 1918, it killed more than 10,000 people per week in some U.S. cities.
The pandemic swept not only North America and Europe, but also spread as far as the Alaskan wilderness and remote Pacific islands. The disease was exceptionally severe, with mortality rates of 2.5 percent among those infected, compared to less than 0.1 percent in other influenza epidemics.
Studying what made the Spanish flu so lethal is important because influenza viruses continually evolve. An understanding of the genetic makeup of the most virulent influenza strain ever seen could help health officials manage possible pandemics in the future.
For their new study, the British scientists sequenced sections of the 1918 influenza virus's genome, using samples from flu victims preserved in the Alaskan permafrost.
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