Oncogenic viruses are viruses that can lead to cancer in humans and animals. They do this by altering the normal function of cells, often by integrating their genetic material into the host's DNA. This can disrupt normal cell regulation, leading to uncontrolled cell growth and tumor formation. Examples of oncogenic viruses include Human Papillomavirus (HPV), Hepatitis B virus (HBV), and Epstein-Barr virus (EBV). These viruses are significant in public health because they are linked to various cancers. For instance, HPV is associated with cervical cancer, while HBV can lead to liver cancer. Understanding oncogenic viruses helps in developing vaccines and treatments to prevent virus-related cancers.