Infection causes of cancer
Worldwide approximately 18% of cancer deaths are related to infectious diseases.
This proportion ranges from a high of 25% in Africa to less than 10% in the developed world.
Viruses are the usual infectious agents that cause cancer but cancer bacteria and parasites may also play a role.
Oncoviruses (viruses that can cause cancer) include human papillomavirus (cervical cancer), Epstein–Barr virus (B-cell lymphoproliferative disease and nasopharyngeal carcinoma), Kaposi's sarcoma herpesvirus (Kaposi's sarcoma and primary effusion lymphomas), hepatitis B and hepatitis C viruses (hepatocellular carcinoma) and human T-cell leukemia virus-1 (T-cell leukemias).
Bacterial infection may also increase the risk of cancer, as seen in Helicobacter pylori-induced gastric carcinoma.
Parasitic infections associated with cancer include Schistosoma haematobium (squamous cell carcinoma of the bladder) and the liver flukes, Opisthorchis viverrini and Clonorchis sinensis (cholangiocarcinoma).
