"The threat to bio-security is not as big as everybody thinks," Ron Fouchier, whose team at the Rotterdam Erasmus Medical Centre announced the mutant version in September, told AFP.

"Recreating this virus is definitely not easy. You need highly-skilled people and a very large team, as well as specialised facilities to do this type of work," he said.

Two top scientific journals said Tuesday they were mulling whether to publish full details on how Dutch scientists mutated the H5N1 flu virus in order for it to pass from one mammal to another.

Researchers genetically altered the bird flu strain in a lab, making it airborne and likely to be contagious between humans for the first time.

The research has sparked fears that a pandemic causing millions of deaths could be triggered if it emerged in nature or fell into hands of bio-terrorists or rogue countries.

A US government science and advisory committee urged the US journal Science and the British journal Nature to withhold key details of Fouchier's team's research, so that people seeking to harm the public would not be able to manufacture the virus.

Fouchier however said his team believed publishing the full findings, including a detailed description of the mutated virus, how it becomes airborne and its migration patterns, could help save lives in case of an outbreak.

"These are important details that we need to get out very quickly. This is information that needs to be shared with countries where H5N1 viruses cause outbreaks so that the countries can now be on the lookout if these mutations arise," he said.

He said however his team would respect a recommendation by the US National Science Advisory Board for Biosecurity (NSABB) that the journals withhold key details on their work, saying redrafts of their findings had been re-submitted for approval before the board.

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

The controversy arose when two separate research teams -- one in the Netherlands and the other in the United States -- separately found ways to alter the H5N1 avian influenza so it could pass easily between mammals.

Until now, bird flu has been rare in humans, but particularly fatal in those who do get sick. H5N1 first infected humans in 1997 and has killed more than one in every two people that it infected, for a total of 350 deaths.

Based on fears that a deadly global pandemic could result if the mutant flu escaped a lab or if a terror group were to find out how to make it, a US advisory panel on Tuesday urged scientific journals to hold back key details.

The data "clearly has public health benefit but it has the potential to be used in nefarious ways by some people," said Fauci, who heads the National Institute of Allergy and Infectious Diseases.

The National Science Advisory Board for Biosecurity (NSABB), made up of 23 non-governmental experts, voted unanimously that studies should be published in the journals Science and Nature, but with limited information.

Fauci said that any "legitimate" researchers would be able to seek the full details for their own study.

"If their credentials are appropriate they will have access to that information. So it's not like classified information," he told AFP.

"It's only for those people who have a need to know and have a legitimate purpose for it, as opposed to just throwing it out there so that anybody can do whatever they want," he added.

"It's absolutely not censorship because if you are a scientist and you have the need to know... you will definitely get that information."

The two research teams were funded by grants from the National Institutes of Health, and are in the process of working out changes to their manuscripts with the journals Nature and Science.

Fauci also said that fears of what the mutant virus might do have been overblown. For instance, just because it could be passed easily between ferrets does not necessarily mean it could be as easily transmitted between humans.

"There is a little bit of an overreaction," he said, calling reports of a "monster virus" a "bit dramatic."

The real concern is that H5N1 might mutate in nature and become an influenza that humans could catch and transmit easily, so knowing what those flu features might look like is an important research and surveillance tool, he said.

"We could give that information to the people who are out of the field doing the surveillance, the health officials in Vietnam, Indonesia or China... so they will have a better chance of recognizing as the virus starts to evolve," he said.

"So the scientific question is very legitimate."

Fauci said the NSABB's request for redaction was the first time the advisory committee had made such an appeal, and acknowledged that it was not popular in all corners of the science world.

"There are many scientists who don't agree with the committee. So we need to re-look at what the rational for that decision was, so we can all get together in an open and a transparent way, come up with some more concrete guidelines of what needs to be looked in these cases," he said.

"That is going to trigger some interesting dialogue, I believe."