Many cancers in animals, plants and birds have been recognized to be caused by viruses. Currently, it is being convincingly stated that leukaemia and Hodgkin’s disease— i.e. a malignant disease of lymphatic tissue—are associated with some kind of virus.
Association of Hepatitis-B virus with primary liver cancer is now fairly well established. The African lymphoma described by Burkitt in 1958, is suspected to be due to Epstein-Barr virus.
Although in 1911, Peyton Rous first showed that a virus Mused sarcoma in chickens, it was not until the late 1950’s and early 1960’s with the isolation of the murine (mice) leukaemia viruses and the discovery of the polyoma virus, that serious consideration was given to a virus etiology or cause lor human cancer and great expectations for control with vaccines were generated.
When these viruses enter the cells they are supposed to upset the normal chemical reaction inside the cells which leads to mutation of these cells into cancer cells.