The hurriedly-assembled meeting is designed to try and settle an unprecedented row over a call to ban publication of two scientific studies which detail how to mutate H5N1 bird flu viruses into a form that could cause a deadly human pandemic.

But experts say whatever the outcome, no amount of censorship, global regulation or shutting down of research projects could stop rogue scientists getting the tools to create and release a pandemic H5N1 virus if they were intent on evil.

"It doesn't matter how much you restrict scientists from doing good, bad people can still do bad things," said Wendy Barclay, an expert in flu virology at Imperial College London.

The WHO called the meeting, for February 17 and 18 in Geneva, to work out how to break a deadlock between scientists who have studied the mutations needed to make H5N1 transmit between mammals and U.S. biosecurity chiefs who want their work censored or "redacted" before it goes into scientific journals.

Since the two research teams, one in the Netherlands and one in the United States, have found that just a small number of mutations would allow H5N1 to spread like ordinary flu between mammals - and remain just as deadly as it is now - the meeting is likely to be tense and highly secretive. WHO officials repeatedly stress it will be a "closed door" event.

DEEP CONCERN

The United Nations health body has said it is "deeply concerned about the potential negative consequences" of work by the two leading flu research teams who in December said they had found ways to make H5N1 into a easily transmissible form capable of causing lethal human pandemics.

Flu researchers from around the world - more than 30 teams in all - declared a 60-day moratorium starting on January 20 on "any research involving highly pathogenic avian influenza H5N1 viruses" that produce easily contagious forms of the virus.

The WHO has invited 22 people to this week's meeting, including the researchers who carried out the work, editors of the two journals, Science and Nature, who were asked to hold publication, and representatives from the U.S. National Science Advisory Board for Biosecurity (NSABB) which asked for the papers to be censored.

Keiji Fukuda, the WHO's Assistant Director-General for Health Security and Environment, who will chair the meeting, says he would like to secure agreement on whether the studies should be published, in full or part, and who should have access to them.

The scientific know-how is seen as vital for scientists to be able to develop vaccines, diagnostic tests and anti-viral drugs that could be deployed in the event of an H5N1 pandemic.

"It is important that research on these viruses should continue," Fukuda told Reuters. "They do pose a risk. There's a lot of things we don't know about them. The question is not really should we continue to do research ... but under what conditions can we do it so we don't unnecessarily create fears and risks."

The H5N1 virus, first detected in Hong Kong in 1997, remains entrenched among poultry in many countries, mainly in Asia, but so far remains hard for humans to catch. It is known to have infected nearly 700 people worldwide since 2003, killing half of them, a far higher fatality rate than the H1N1 swine flu which caused an influenza pandemic in 2009/2010.

Ron Fouchier, the scientist leading the Dutch team that gave H5N1 various genetic mutations and made it transmissible in mammals, argues the research must be published to help public health officials better prepare for a scenario where the virus could mutate and become more deadly, spreading from person to person via coughs and sneezes.

He has also said other research teams around the world are close to the same findings, some of them inadvertently, and should be warned in advance how the virus could become airborne.

In the short term, most scientists agree the moratorium is "a good gesture," as flu expert and former WHO health security adviser David Heymann describes it, one that offers the research community space to think.

SUPER STRAINS

But can it, or should it, go on forever?

Heymann, Barclay and many other scientists argue that stopping this type of research into flu viruses and other potentially lethal pathogens would set a dangerous precedent.

Although adding and deleting genes can create super-strains that put the entire world at risk, Heymann said, such work is also vital to developing tools such as effective vaccines and diagnostic tests which are needed quickly if a pandemic hits.

Preventing this research would also prevent legitimate and well-intentioned researchers from using all possible scientific options to prepare for naturally occurring, or deliberately caused, outbreaks.

John Edmunds, who heads the department of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine, describes studies on genetic mutations of H5N1 as "very, very important work" that should not be stopped.

"This flu strain has the potential to cause such enormous damage, and it's important to know how far away we are from a horrible event like that," he said. "It appears we're not that far off it. That doesn't mean it's inevitably going to happen, but it makes it more important that we're vigilant."

Heymann, who now leads the Center on Global Health Security at the Chatham House think-tank in London, says the best possible outcome would be a globally-agreed "best practices framework on how you conduct this research and how you provide the information to others."

"It's also crucial to get understanding that even if you don't provide this research information, there are ways that rogue scientists can get it if they want to," he said.

(Writing by Kate Kelland; Editing by Janet Lawrence)

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