Scientists will have the technology to create a wholly artificial virus within the next five years, a major conference in the US has been told.

The synthetic microbe could be used to help genetically engineer novel plants and animals, and treat human disease.

But if the technology is abused, it could lead to bioweapons against which society might have little defence.

The timetable for the creation of an artificial virus was laid out by Professor Clyde Hutchinson, of the University of North Carolina and The Institute of Genomic Research.

"This isn't trivial to do and no-one has yet reported doing it," he told the annual meeting of the American Association for the Advancement of Science (AAAS).

But he said: "If researchers put their minds to it, they could do it within a few years."

'Bad stuff'

Delegates to the annual meeting stressed that the issues surrounding a synthetic virus should not be over-dramatised.

Dr Jonathan Moreno, of the University of Virginia, and an author on bioweapons, said rogue states or groups already had access to plenty of destructive technologies.

{picture} Some fear the new technology could be used to create bioweapons

"A synthetic virus is something to be concerned about, but the question is whether we could develop anything that is worse than what is already available in nature, that some have attempted to exploit for the purposes of bioweaponry - such as anthrax," he said.

"There's enough bad stuff out there now. So far, there is no reason to believe that this technology is going to make things any worse."

Professor Hutchinson and his fellow researchers are engaged in what is known as the Minimal Genome Project, which is investigating the smallest number of genes required to sustain life.

From scratch

The project may eventually provide the knowledge to create an artificial lifeform - most probably a small bacterium.

Such a lifeform would be built from scratch using fundamental chemicals and could be engineered to manufacture useful drug components or to break down chemicals at the site of a toxic spill.

But Prof Hutchinson told the AAAS synthetic lifeforms were still science fiction because of the difficulties in synthesising long segments of nucleic acid - the "life molecule" DNA and its chemical cousin RNA.

{picture} A synthetic microbe could be used to treat disease

He said: "Just having the genome isn't the same as having a cell.

"To get the genes to do something, there have to be factors there to translate the genes into messenger RNA and into proteins, etc, and that at present can only be done in a living cell."

Most researchers would not regard a virus as being "alive", as it depends on the machinery of a living, host cell to replicate.

But its very much simpler design - nucleic acids perhaps just 10 kilobases in length and a few associated proteins - makes it an easier target for synthesis.

Although viruses are popularly seen as merely agents of disease, they also have a productive role in biotechnology.

Modified versions of viruses, in which the disease-causing elements have been "switched off", can be used to carry useful genes into an organism.

Design flexibility

Viruses could be important tools in future gene therapy, carrying genes into the cells of sick people to correct or replace the ones that have gone wrong.

A synthetic virus might make this task easier by providing greater flexibility of design.

The fear would be that the same technology could be used to synthesise a super-pathogen, or "biobomb", to terrorise society.

But Dr David Magnus, of the University of Pennsylvania Center for Bioethics, said any minded individual would probably opt for a simpler approach.

He said: "You don't have to synthesise a genome from scratch to be able to make a version of smallpox.

"You could get a close relative and use standard genetic engineering. You could probably do that right now."

Professor Daniel McGee, of Baylor University, said the threat always had to be judged against the benefits, with regulation steering us on the right course.

"We're toolmakers. The first axe could have been used for agricultural purposes and good purposes, or it could have been used for killing.

"The moral dilemma is essentially the same.

"The fact that there is more power now - it extends further than just one person with one axe - is significant, but it doesn't change the qualitative dimension of the moral dilemma."

Prof Hutchinson added: "Am I worried about a synthesised virus? No, you only worry about it if someone does it out of malicious motives."