IN DECEMBER the scientific world was taken aback by an odd request. The American government, in the shape of the country's National Scientific Advisory Board for Biosecurity (NSABB), called on the world's two leading scientific journals to censor research. Nature and Science were about to publish studies by researchers who had been tinkering with H5N1 influenza, better known as bird flu, to produce a strain that might be able to pass through the air between people. The NSABB fretted that were the precise methods and detailed genetic data to fall into the wrong hands, the consequences would be too awful to contemplate. They suggested that only the broad conclusions be made public; the specifics could be sent to vetted scientists only.

H5N1 is undoubtedly dangerous. Some 60% of the 570 recorded human cases have been fatal (though non-fatal ones are less likely to be recorded). On January 20th, therefore, the research teams' leaders, Ron Fouchier of the Erasmus Medical Centre, in Rotterdam, and Yoshihiro Kawaoka of the University of Wisconsin-Madison, bowed to public pressure. In a joint statement published in both Nature and Science, which was also signed by 37 other leading flu experts, they announced a voluntary 60-day moratorium on all similar research. The aim of this self-imposed suspension, they explained, was to give organisations and governments time “to find the best solutions for opportunities and challenges that stem from the work.”

For a start, that means working out a way to disseminate the sensitive nitty-gritty to the right people, a condition that both publications said must be met if they are to remove these details from the public versions of the papers. It also involves deciding how, if at all, future research should be carried out. These and other topics will be discussed at a summit that the World Health Organisation (WHO) hopes to hold in Geneva, in February. The signatories are hoping that by showing themselves to be acting responsibly in this way they will prevent heavy-handed regulation from stifling their field.

Even before interested parties convene in Switzerland, though, fierce debate has got under way. In the January 19th issue of Nature, ten experts, including Dr Fouchier, weighed in on the matter. Science launched a similar policy forum. One immediate conclusion is that flu researchers are divided among themselves. Some are frustrated by what they see as overblown misgivings by the NSABB. Others praise the NSABB's intervention as prescient.

One prominent critic, Peter Palese, of the Mount Sinai School of Medicine in New York, recalls his own work in 2005 on the reconstruction of the Spanish-flu virus. Spanish flu was an epidemic that peaked in 1918, and which may have claimed as many as 100m lives. At the time, the NSABB held its nerve, apparently concluding that the benefits of full disclosure outweighed the risks. Dr Palese points out in Nature that his success prompted many other researchers to enter the field. The resulting surge of papers revealed that the virus is vulnerable to existing seasonal-flu vaccine and common drugs, allaying fears that mischief-makers would conjure it up and wreak havoc.

The researchers in Rotterdam and Madison have shown that viruses containing haemagglutinin (a protein which causes red blood cells to clump together) from H5N1 strains can be passed through the air between ferrets. (When it comes to flu, ferrets and humans are very much alike.) They also identified the genetic markers of the lethal strain and showed that not all strains are as deadly. In a comment article in Nature Dr Kawaoka stresses that such information is crucial to the development of effective vaccines and drugs. It also enables authorities to monitor outbreaks of bird flu for the dangerous mutations and so nip a potential epidemic in the bud.

Michael Osterholm, of the University of Minnesota, and Donald Henderson, of the University of Pittsburgh, however, argue in Science that H5N1's human-fatality rate means any benefits that might flow from the research are dwarfed by the risks. Although some research is warranted, they say, there is no need to share the mutation data “outside of a small select group of established researchers already working within the WHO network.”

The WHO, for its part, said in a statement to Science that research like that of Dr Fouchier and Dr Kawaoka is “an important tool for global surveillance efforts”. The organisation also worries that limiting access to relevant findings would be difficult to square with its recently updated pandemic influenza preparedness framework. This agreement, which stipulates that countries which provide virus samples should also receive the benefits of research, was preceded by four years of rancorous debate. If anything can be said for certain, then, it is that the gulf between those in favour of tighter controls and those against will be hard to bridge in a mere two months.