Worldwide approximately 18% of cancers are related to infectious diseases. Viruses are usual infectious agents and a virus that can cause cancer is called an oncovirus.
Human Papilloma Virus (HPV) - a DNA virus that infects keratinocytes of the skin or mucous membranes. While the majority of the known types of HPV cause no symptoms in most people, some types can cause warts (verrucae), while others can -in a minority of cases- lead to cancers of the cervix, vulva, vagina, penis, oropharynx and anus.
Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) - they can induce a chronic viral infection that leads to liver cancer in about 1 in 200 of people infected with hepatitis B each year and in about 1 in 45 of people infected with hepatitis C each year.
Helicobacter pylori- even if it is not a virus, is a Gram-negative bacterium that is present in patients with chronic gastritis and gastric ulcers and it is linked to the development of duodenal ulcers and stomach cancer.