The scientists had set out to develop a biological contraceptive intended to halt mouse and rat plagues. They added a gene involved in the mouse immune system to the mousepox virus, a smallpox-like disease that affects mice.
But in doing so, they made the virus deadly for breeds of laboratory mice normally resistant to its effects. They also found it made vaccines for mice against mousepox less effective, said Dr. Bob Seamark, director of the Cooperative Research Center for the Biological Control of Pest Animals.
Humans have a similar immune system gene, and it was not clear if the same process could create a pathogen deadly to people. Scientists say the mouse virus itself poses no danger to humans.
Seamark said last week the world should be warned of the potential abuses of the discovery if similar manipulation is done with human viruses.
"It was a concern that this same modification could be made to human viruses and this would enhance their virulence or at least (strengthen) their ability to kill people," he said.
"We also want researchers to use this new knowledge to help design better vaccines."
Dr. Annabelle Duncan, chief of molecular science at the Australian government's Commonwealth Scientific and Industrial Research Organization, urged a stronger Biological Weapons Convention, a treaty ratified by some 140 nations pledging not to develop or stockpile biological weapons.
"Discoveries such as this are being made all the time," she said. "The important thing is to ensure they are used for good, not for destructive purposes."
A report on the discovery is scheduled to be published in the February issue of the Journal of Virology.
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