Leading influenza scientists have ended a self-imposed moratorium on research into what it might take to make bird-flu viruses transmissible among humans.
The international group announced its intention to resume work in the controversial field in a letter published jointly today by the journals Nature and Science.
The decision brings to a close a moratorium that was meant to last two months, but instead stretched for just over a year.
"It's a long 60 days," said Ron Fouchier, a Dutch virologist whose laboratory at Erasmus Medical Centre in Rotterdam is a world leader in this work.
The scientists said that because of the risks posed by the H5N1 flu virus, they have a public-health responsibility to resume this research.
The moratorium was offered as a good-faith gesture last January, when the flu community was embroiled in a controversy over two studies that showed how H5N1 viruses could be made to spread between ferrets, in the way regular flu spreads among humans. Fouchier's lab produced one of the studies.
Advisers to the U.S. government argued it would be a biosecurity risk to publish the changes that made the virus transmissible among mammals, but in the end, the two studies were published in May and June.
"We fully acknowledge that this research … is not without risks," the scientists said in their letter. "However, because the risk exists in nature that an H5N1 virus capable of transmission in mammals may emerge, the benefits of this work outweigh the risks."
The moratorium has covered only H5N1 studies that relate to what is called gain of function – changing the virus to enhance its transmissibility or virulence.
Currently, the H5N1 virus occasionally infects people, but does not spread person to person in the way human flu strains do.
Scientists had been trying to figure out whether the virus could evolve to acquire that capacity and what changes it would need to do so. They argue knowing the mutations needed for person-to-person spread will arm those laboratories that monitor the strains circulating in nature to spot viruses that might be making the transition.
The controversial studies showed as few as between five and nine mutations may be all that is needed to give the viruses the ability to transmit from ferret to ferret through airborne droplets, the way flu viruses can spread among people. Some H5N1 viruses already have a couple of those changes.
Today's letter was signed by all 39 of the original signatories to the moratorium, as well as a Russian scientist who signed on shortly after the original letter was published in January, 2012.
The letter acknowledges that work cannot immediately resume for U.S.-based or U.S.-funded researchers, because the Department of Health and Human Services is still finalizing a framework for how such work will be approved in future.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said he thinks that process is a few weeks — "not months" — from completion.
Fouchier has U.S. funding. But his research is also supported by the European Union, so he is taking steps to get his laboratory back into action.
"We think that this is still a pressing issue. These viruses have the potential to evolve in nature. And we could keep this work shut down for another few years and then be caught by surprise," he said. "That's a responsibility I would not like to take. And I've been convinced from the beginning that this work can be done safely and is done safely by the laboratories who are doing it."
But a leading scientist who argues that this work should not be undertaken called the lifting of the moratorium "outrageous."
"I think it's just a snow job," Richard Roberts, a 1993 Nobel Prize winner for medicine, said when asked whether his concerns about the work had been assuaged by the various international meetings that have taken place over the last year and the protocols that have been developed in that time.
"I've not heard very much from people who were outside of the flu community," Roberts said, arguing that researchers who oppose the work are afraid to speak up for fear their funding from the U.S. National Institutes of Health might be threatened if they do.
Roberts said he does not agree that this work must be done to protect against a possible H5N1 pandemic. He said there is no way to guarantee that results seen in the lab under artificial conditions will mimic what is seen in the wild.
Fauci insisted, though, that the issue has had a full airing, with multiple international meetings involving biosecurity experts, lab-safety experts and others. "So I don't think people can say the effort was not put into trying to discuss this in an open and transparent way," he said.
The World Health Organization reports that as of mid-January, there have been 610 confirmed H5N1 infections in 15 countries; 360 of those people have died.