For many years we have know a virus causes cancer in animals and humans. Here are some:
Human Papillomavirus (HPV) Cervical, anal, oropharyngeal, and penile cancers
Epstein-Barr Virus (EBV) Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma
Hepatitis B Virus (HBV) Liver cancer (hepatocellular carcinoma)
Hepatitis C Virus (HCV) Liver cancer
Kaposi's Sarcoma-Associated Herpesvirus (KSHV) Kaposi's sarcoma, primary effusion lymphoma
Human T-Lymphotropic Virus (HTLV-1) Adult T-cell leukemia, tropical spastic paraparesis
Merkel Cell Polyomavirus Merkel cell carcinoma
There are more that are not listed and more are to come. It would be good to cease eating animal flesh and their milk or eggs. They can carry virus's that cause human cancer.
One that is not listed was discovered by a study done by UC Berkley. They discovered that Bovine Leukemia Virus causes Breast Cancer.
More information can be found at
cancer.org