A recent study suggests that Alzheimer' s disease, which attacks the human brain, may be caused by a virus  In the study, blood from 11 volunteers, each of whom had the disease, was injected into rats  The rats eventually exhibited symptoms of another degenerative neurological disorder, Creutzfeldt-Jakob disease, which is caused by a virus
This led the scientist who conducted the study to conclude that Alzheimer' s disease might be caused by a virus
Alzheimer's disease in rats is not caused by a virus.