THERE are some Hollywood fantasies you'd like to see in the real world. Hoverboards and Happy Places, for example.

Then there are the Hollywood nightmares that you'd rather not think too much about. Or rather governments with huge military budgets wouldn't think about.

Such as the airborne virus which this year almost wiped out the population of the world in Contagion.

Obviously, the US government aren't huge Steven Soderbergh fans, having paid scientists to figure out how the deadly bird flu virus could mutate to become a bigger threat to humans.

They then demanded virologists researching the work don't release full details of their success.

That's because it has been revealed that two labs succeeded in creating new strains of H5N1 that are easier to spread. "Easier" as in "airborne".

"I can't think of another pathogenic organism that is as scary as this one," US National Science Advisory Board for Biosecurity (NSABB) chair Paul Keim told Science back in November.

"I don't think anthrax is scary at all compared to this."

At the time, Science described the new strain as a virus "that could change world history if it were ever set free".

It had been genetically altered so it could be transferred easily between ferrets, the animals which most closely mimic human response to flu.

Passing the flu from one ferret to another, the team discovered the H5N1 strain mutated into an airborne virus. Until now, that was the key factor in the virus limited it to something unlikely to cause a pandemic.

Science described the possibility of an H5N1 pandemic as a scenario that "keeps flu scientists up at night", because in all the known cases of human infection to date, more than half have been fatal.

This morning, the US Department of Health and Human Services (HHS) took the unprecedented step of asking two teams researching the new virus not to publicise all the details of how it was created.

They admit the research had lots of potential to help the public, but feared it might also be hijacked by would-be bioterrorists.

The teams that wrote papers about the new virus reluctantly agreed to redact data from manuscripts to be submitted to scientific journals Science and Nature for publication.

"It wasn't an easy decision," said Dr Anthony Fauci, infectious diseases chief at the National Institutes of Health, which funded the original research.

A statement from the NSABB recommended "that the general conclusions highlighting the novel outcome be published, but that the manuscripts not include the methodological and other details that could enable replication of the experiments by those who would seek to do harm".

Editor-in-chief of Nature, Dr Philip Campbell, said he understood the motivation behind the redaction, but it was "essential for public health that the full details of any scientific analysis of flu viruses be available to researchers".

Lethal strains

The H5N1 strain of bird flu is fatal in 60 per cent of human cases but only 350 people have so far died from the disease, largely because it cannot - yet - be transmitted between humans.

Editors from the journals Science and Nature said they were considering the US government's request.

Science editor-in-chief Bruce Alberts said scientists could benefit from knowing about the virus because it could help speed new treatments to combat this and other related lethal forms of influenza.

"Many scientists within the influenza community have a bona fide need to know the details of this research in order to protect the public, especially if they currently are working with related strains of the virus," he wrote.

"Science editors will be evaluating how best to proceed," he added, asking for more clarification on how the government would make the information available to "all those responsible scientists who request it."

Human-to-human

The Dutch research team was led by Ron Fouchier at Rotterdam's Erasmus Medical Centre.

The team said in September it had created a mutant version of the H5N1 bird flu virus that could for the first time be spread among mammals.

Fouchier said in a statement his team had discovered that transmission of the virus was possible between humans "and can be carried out more easily than we thought."

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