The placement of viruses in the aetiology of cancer.

The role of viruses as causative agents of cancer in man has been examined for more than 50 years. These studies have recently been intensified by employing newly developed, more sensitive techniques in virology and immunology. In spite of proof that viruses cause cancer in animals and that about one-quarter of the known 600 viruses possess oncogenic potential, definite proof of their aetiology in human cancer remains elusive even though cancer research is a highly respectable and costly pursuit. Nevertheless, the probabilities are high that human cancer viruses have been and will be identified and that their induced diseases can be prevented or controlled. It is accepted that some benign tumours of man (such as warts) are induced by a virus infection. This article examines the current situation and highlights the difficulties, hopes and usefulness of research in this field.