Researchers developing extra-contagious strains of H5N1 avian influenza have agreed to pause their work for 60 days.

The moratorium, announced Jan. 20 in Nature and Science, is a response to public fear and alarm in the scientific community, which has split over whether the research could inadvertently lead to release of a nightmare disease.

Depending on perspective, the moratorium is either a genuine recognition of the need for broader discussion or a public relations gesture. Either way, it’s a chance for everyone to catch their breath without reaching for a mask.

Fear that the viruses “may escape from the laboratories has generated intense public debate in the media on the benefits and potential harm of this type of research,” the researchers wrote in an open letter declaring the moratorium. “To provide time for these discussions, we have agreed on a voluntary pause of 60 days on any research involving highly pathogenic avian influenza H5N1 viruses leading to the generation of viruses that are more transmissible in mammals.”

The controversy began in November when ScienceInsider reported that two teams of virologists—one led by Ron Fouchier of Erasmus Medical Center in the Netherlands, the other by Yoshihiro Kawaoka at the University of Wisconsin—had developed H5N1 strains capable of passing easily between ferrets, which are used as models for influenza infection in humans. Whether the strains are as easily transmissible between people isn’t known, but is considered possible.

In humans, H5N1 is extraordinarily virulent—mortality runs between 60 and 80 percent—but far less contagious, requiring prolonged contact with infected birds or people. That it could become more contagious is a public health fear of the first order: Containing an outbreak would be extremely difficult, perhaps impossible, and millions of people would almost certainly die. It’s also a fear full of scientific unknowns. Despite a seemingly simple genome containing just a handful of genes, scientists don’t know what mutations could make H5N1 more transmissible between humans.

The research by Fouchier, Kawaoka and other labs was intended to identify those mutations, giving researchers an idea of what to look for in naturally evolving influenza, and perhaps allowing for early warning of strains that are just a few mutations away from causing human pandemics. But when the general outlines of the research became public—detailed descriptions await formal publication, and key details will be redacted at the request of a federal biosecurity committee—outrage followed.

Critics, including many high-profile virologists, epidemiologists and biosecurity experts, said it was possible that would-be biological terrorists could use the research to develop weaponized flu strains. Another, perhaps more frightening possibility was unintentional release: dozens of accidental infections (PDF) have occurred at high-security laboratories in the United States, and it’s thought that one now-global flu strain may actually have escaped from a Russian laboratory in the 1970s. Against these risks, the benefits were arguable, and some virologists even said that mutations engineered in a laboratory didn’t necessarily illuminate future dangers.

"The research should never have been undertaken because the potential harm is so catastrophic and the potential benefits from studying the virus so speculative," opined the New York Times in a Jan. 8 editorial entitled "An Engineered Doomsday."

By declaring the 60-day moratorium, which will pause both further H5N1 engineering and experiments on the existing mutant strains, the researchers attempt to allay these fears.

"We recognize that we and the rest of the scientific community need to clearly explain the benefits of this important research and the measures taken to minimize its possible risks," they write. "We propose to do so in an international forum in which the scientific community comes together to discuss and debate these issues."

Reception to the moratorium appears mixed. Michael Osterholm, head of the University of Minnesota’s Center for Infectious Disease Research and Policy and a member of the federal committee that recommended redacting the findings, told Nature News that 60 days is far too short a time for developing any meaningful policies. "I just don't think that’s realistic," he said.

Richard Ebright, a Rutgers University microbiologist and vocal critic of the research, called the moratorium "an empty gesture. Strictly public relations."

Contrary to the researchers' insistence that the work was "using the highest international standards of biosafety and biosecurity," it was conducted at so-called Biosafety Level 3—a set of techniques and safeguards less strict than is used for Ebola and the Marburg virus, which pose less potential threat than an H5N1 strain that easily infects people. And outside of biosafety committees at researchers’ institutions, there appears to have been no official discussion of potential safety risks until the controversy made it unavoidable.

Through the moratorium, the researchers are "seeking only an opportunity to 'explain the benefits of this important research and the measures taken to minimize its possible risks,' thereby educating benighted policy makers and the public, eliminating their 'perceived fear,'" said Ebright, quoting the moratorium’s announcement. "We do not need to hear anything from the virus cowboys. They need to hear from us."