An oncovirus is a type of virus that can cause cancer in animals and humans. These viruses can alter the genetic material of host cells, leading to uncontrolled cell growth and tumor formation. Some well-known oncoviruses include certain strains of human papillomavirus (HPV) and hepatitis B virus (HBV). Oncoviruses are classified into two main categories: DNA viruses and RNA viruses. DNA oncoviruses integrate their genetic material into the host's DNA, while RNA oncoviruses typically convert their RNA into DNA before integration. Understanding oncoviruses is crucial for developing vaccines and treatments for virus-related cancers.