The World Organisation for Animal Health (OIE) has said that most remaining laboratory stocks of a devastating cattle disease should be destroyed to ensure the eradicated virus is not back into nature.
"If someone laid their hands on an eradicated virus it could cause a global disaster," OIE chief Bernard Vallat said.
The OIE announced last year the eradication of the viciously contagious and often fatal rinderpest virus, also known as cattle plague, making it only the second virus after smallpox in humans ever to be expunged from living beings.
The problem, Vallat told AFP after speaking at a Biological Weapons Convention meeting in Geneva, is that dozens of laboratories around the world still have samples of the virus, which has been a curse to livestock farmers throughout the ages and which has often contributed to famines that in turn have fuelled turbulence and war.
"Among these laboratories, there are some that are not at all in line with safe bio-security standards," he said, pointing out that there is a risk the virus, by accident or intentionally, "could find itself back in nature and could start killing again."
If the virus were to reappear it could spread like wildfire among livestock that is no longer vaccinated against it, he said.
To ensure that the world remains free from the disease, Vallat said his organisation was calling on all countries to either destroy their remaining stocks of the virus or to transfer their stocks to approved reference labs.
The OIE and the UN's Food and Agriculture Organization (FAO) had called for a moratorium on all research using the live rinderpest virus, he said.