Viruses and cancer

About one-fifth of human cancers worldwide arise in the stomach (9%), liver (6%) or cervix (5%), and most of these would be prevented if these infections could be eradicated. A subgroup of sexually transmitted human papillomaviruses (HPV) including HPV16, HPV18 and HPV45 is detectable in almost all cervical cancers. The contribution of hepatitis B virus to hepatocellular carcinoma in high-incidence regions has long been recognized and hepatitis C virus is similarly carcinogenic. Other viruses that present a substantial cancer risk in certain populations include Epstein-Barr virus (associated with various lymphoid malignancies and nasopharyngeal cancer), HTLV-1 (adult T-cell leukaemia/lymphoma), HIV (non-Hodgkin's lymphoma) and human herpesvirus-8 (Kaposi's sarcoma). There is strong epidemiological evidence for an infective aetiology in childhood leukaemia, but no specific pathogen has been identified.