Viruses in human cancers

Infections have been recently identified as important etiologic factors for an increasing percentage of human cancers. Between 15 and 20% of the globa l burden of human cancers have been linked to viral, bacterial and parasiti c infections. Viruses play a major role, since two types of infections, ano genital papillomavirus types and Hepatitis B virus account for about 15% of cancers in females and slightly less than 10% of cancers in males. This re view summarizes the criteria used for the identification of carcinogenic in fectious agents, analyses some of the known mechanistic contributions of vi ruses to carcinogenesis, presents some host and host cell responses to thes e infections, and discusses prospects for the prevention and therapy of vir us-linked cancers.