[Virus as an etiological factor of cancer in human beings]

Human oncogenic viruses are heterogenous as a group but share the property of causing persistent and often lifelong infections. Immortalization of host cells is seen in some but not all infections. Chromosomal instability of the infected cells is probably important. Epidemiological data indicate that viral oncogenesis in humans is a multifactorial process where host factors such as age, race, sex and immune-competence, and exogenous factors such as coinfections and cocarcinogens, are important determinants.