Using tiny pieces of preserved lung tissue and a body frozen in the Alaska tundra, a team of scientists were able to recreate the 1918 Spanish flu virus, an achievement that may help uncover how the current deadly strain of bird flu could become transmittable between humans.

The results, published in the journal Nature in October 2005, offered some parallels between the Spanish flu virus and the H5N1 strain of the bird flu slowly spreading through Asia and recently turning up in other parts of the world.

By late October 2005, the bird flu, which can be transmitted from birds to humans, had killed 60 people, mostly in Vietnam. Evidence of the disease also has been discovered in birds in other countries, including Croatia, Turkey, Romania, Russia and Greece.

Four of the eight genes in the H5N1 strain contain mutations seen in the deadly Spanish flu 87 years ago, according to the published reports.

When the Spanish flu struck in late winter 1918, it quickly spread around the globe, killing 50 million people by the spring of 1919. Only American Samoa and parts of Iceland were spared. It had an unusually high death rate in otherwise healthy people aged 15-34.

At the time, microbiologists didn't know what caused the widespread deaths; the influenza virus was not identified until 1933. And as the Washington Post reported, although biologists later were able to determine the broad family of influenza viruses the 1918 strain came from, its genetic identity was lost.

That is, until Jeffrey Taubenberger, a molecular pathologist at the Armed Forces Institute of Pathology in Rockville, Md., and his team toiled for 10 years to piece together the deadly virus in a high-security laboratory at the Centers for Disease Control and Prevention in Atlanta.

They got their samples from small pieces of lung tissue, preserved in wax after the autopsies of two soldiers among the Spanish flu's 675,000 American victims, and from the frozen body of an Inuit woman who died from the virus in November 1918 and was buried in the Alaska permafrost.

The virus' eight gene segments, or strands of RNA, were in fragments, but the team was able to piece them back together using gene sequencing and polymerase chain reaction -- a method of creating copies of specific fragments of DNA.

Analysis of all eight genes showed the Spanish flu came directly from a bird virus and moved into humans after slowly mutating. The analysis suggests that H5N1 also might be capable of spreading between humans through gradual mutations, reported the Washington Post.

Another team of scientists, led by Terrence Tumpey of the CDC and Adolfo Garcia-Sastre of the Mount Sinai School of Medicine in New York City, experimented with the live reconstructed Spanish flu virus and found that mice infected with the microbe died unusually quickly, in three days. The results were published in Science magazine in October 2005.

The 1918 virus was at least 100 times as lethal when compared to another flu virus, a Texas strain of H1N1 from 1991, according to the Center for Infectious Disease Research and Policy.

"Research such as this helps us understand what makes some influenza viruses more harmful than others," said CDC Director Dr. Julie Gerberding in a statement. "It also provides us information that may help us identify, early on, influenza viruses that could cause a pandemic."

In response to concerns over whether publishing both teams' findings would pose a bioterrorism risk, the National Science Advisory Board for Biosecurity reviewed the papers and endorsed their publication.

The techniques described in the studies were not new and were already accessible to those with the means to conduct similar experiments, according to the National Institute of Allergy and Infectious Diseases.

Scientists hope to use the information gleaned from reconstructing the Spanish flu to create new vaccines and treatments.

-- Compiled by Larisa Epatko for the Online NewsHour