New oncogenic human papovaviruses.

Human papovaviruses of the polyoma-SV40 subgroup are common infectious agents. The clinical picture of the primary infection of these viruses is unknown, but one of the viruses, the JC virus, is associated with and probably causes progressive multifocal leukoencephalopathy. These viruses cause tumours and transform cells of several species of laboratory animals. Current results seem to rule them out as a major aetiollogical factor in human cancer. However, their relationship to human tumours requires further study, especially in immunologically compromised patients showing activation of a latent infection.