The team has said the virus does not cause disease in humans.
This virus can also cause swelling of the feet and hands.
In these people, the weakened virus can cause the original disease.
Many viruses cause little or no disease and are said to be "benign".
In the 20th century many diseases both old and new were found to be caused by viruses.
But the scientists who must determine what virus will cause the next year's illness run a high chance of being wrong.
In all other species, the virus causes no obvious disease.
Some human cancers are caused by viruses, but most begin in other ways.
The virus caused a major African famine in the 1920s.
The costs would certainly be less than the disruption to business and communications these viruses cause.