Scientists in the US have rebuilt the deadly Spanish flu virus that swept the world in 1918, killing up to 50 million people, writes Dick Ahlstrom, Science Editor.
It has also emerged that the highly virulent bird flu, which now threatens a human pandemic, has many similarities with Spanish flu.
Dr Terrence Tumpey and colleagues at the Centers for Disease Control and Prevention, Atlanta, used genetic information to reconstruct the Spanish flu virus in a high-security "biosafety level three" laboratory.
The viral genome was recovered from stored lung tissue taken from a patient who caught and died from the 1918 flu. Dr Tumpey used "reverse engineering" to partially rebuild the virus, including the eight genes needed by the Spanish flu to infect a host and replicate.
Two leading international journals, Science and Nature, joined forces yesterday to release details of the latest research findings on the influenza virus. A major killer, flu causes about 500,000 deaths worldwide each year even in the absence of dangerous strains such as Spanish or Hong Kong flu.
The researchers took this radical step as they believe much can be learned about dangerous new strains such as the deadly bird flu, which has infected 115 people and killed 60 in the Far East since 2003. The latest bird flu death, in a 23-year-old man, was confirmed only yesterday in Indonesia.
"We felt we had to recreate the virus and run these experiments to understand the biological properties that made the 1918 virus so exceptionally deadly," Dr Tumpey said. "We wanted to identify the specific genes responsible for its virulence, with the hope of designing antivirals or other interventions that would work against virulent pandemic or epidemic influenza viruses."
His research may prove important given separate findings published yesterday by Dr Jeffrey Taubenberger of the US Armed Forces Institute of Pathology, who released genetic details of the last three Spanish flu genes in Nature.
He found the 1918 virus had several of the same mutations found in the bird flu now spreading in wildfowl and domesticated birds across the Far East. He reported striking similarities between Spanish flu genes and those of flu viruses found only in birds.
This finding suggests that some flu strains can cause serious infection without first combining with a flu strain already adapted to humans.
Scientists use a code to describe flu strains, with the typical annual flu referred to as H3N2. There is widespread worldwide immunity to this strain because of exposure but also winter-time flu shots.
There was almost no immunity to the Spanish flu, H1N1, because it was a new viral mutation, so it swept across the world killing about 5 per cent of those who caught it. Scientists and public health officials are now fearful of a similar pandemic caused by bird flu, H5N1. It is currently killing more than half of those who catch it.
Human bird flu infection rates remain low, but a new pandemic is considered inevitable. Flu pandemics typically occur every 30 years or so. The 1918 flu was followed in 1957 by the H2N2 Asian flu and the 1968 H3N2 Hong Kong flu.