Senior scientific advisers to the World Health Organisation (WHO) have recommended the creation of a genetically modified version of the smallpox virus to counter any threat of a bioterrorist attack.
Permitting researchers to engineer the genes of one of the most dangerous infections known to man would make it easier to develop new drugs against smallpox, the scientists said. But the man who led the successful global vaccination campaign to eradicate smallpox from the wild said he opposed the move on the grounds that the scientific benefits were not worth the risks to public health.
Professor Donald Henderson, of the Centre for Biosecurity at the University of Pittsburgh, said he feared that tinkering with the genetic makeup of the variola virus - which causes smallpox - might accidentally produce a more lethal form of the disease.
"What I worry about is that there is rather too much done in this area and the minute you start fooling around with it in various ways, I think there is a danger," Professor Henderson said. "I'd be happier if we were not doing it and the simple reason is I just don't think it serves a purpose I can support. The less we do with the smallpox virus and the less we do in the way of manipulation at this point I think the better off we are."
Laboratory stocks of smallpox are stored at only two locations - one in America and one in Russia - but there are fears that samples of the virus may have fallen into the hands of terrorists.
Scientists advising the WHO believe that creating a GM form of the virus would accelerate research into developing new antivirals. The WHO is due to consider the recommendations of its scientific committee at the world health assembly in May.
Four years ago, scientists in Australia genetically modified a mousepox virus and inadvertently created a highly virulent strain that could not be stopped by vaccination. But the WHO insisted the latest proposal to engineer the human smallpox virus was inherently safer.
Professor Geoffrey Smith of Imperial College London, who chairs the WHO committee for variola virus research, said American scientists simply wanted to insert a jellyfish gene, which produced a glow under fluorescent light, in order to see the virus better under the microscope.
"The reason why the proposal was made and the reason why the committee was prepared to consider it was that it is clear that there is a need to develop drugs against the virus," Professor Smith said. "The quickest way to screen a large database of compounds is to have an automated way and if you have a virus that expresses the green fluorescent protein you can do the drug screening in a much more rapid and automated way."
It is understood there are seven recommendations in the proposal, including permission to allow relatively large fragments of the virus - up to 20 per cent of its entire genome - to be shipped from the two secure laboratories to other research institutes in the world. Another recommendation allows Russian and US laboratories to snip small fragments of the virus and insert them into other members of the same pox-virus family.
Smallpox is one of the biggest killers in the history of infectious diseases. At least 300 million people died of it in the 20th century alone. It was eradicated in 1977.