Slow-Virus Infections of the Nervous System

THE term "slow infection" has been variously used and defined. I have taken it from the Icelandic worker in veterinary medicine, Dr. Bjorn Sigurdsson, who, returning to Iceland from work in the United States, isolated one viral agent after another from Icelandic sheep, each a virus that behaved very differently from viruses then being isolated in most other parts of the world. For a while it seemed as though slow viruses were purely Icelandic and that Icelandic sheep were unique. Sigurdsson defined slow infection as an infection of the host in which the agent continued to multiply, slowly producing progressive . . .