Infectious agents are responsible for almost 22% of cancer deaths in the developing world and 6% in industrialized countries. Viral hepatitis B and C can cause cancer of the liver; human papilloma virus infection can cause cervical cancer; the bacterium Helicobacter pylori increases the risk of stomach cancer. In some countries the parasitic infection schistosomiasis increases the risk of bladder cancer and in other countries the liver fluke increases the risk of cholangiocarcinoma of the bile ducts. Preventive measures include vaccination and prevention of infection and infestation.
In Canada, HPV-16 and HPV-18 cause about 70% of cervical cancers. HPV is also associated with 80-90% of anal cancers, 40% of vaginal and vulvar cancers, 40-50% of penile cancers and 25-35% of oral cavity and oropharyngeal cancers1. Individuals can reduce their risk of contracting HPV by getting vaccinated for the most commonly cancerous strains, limiting the number of sexual partners and by using a barrier method of protection during sex, such as a condom.
For more information, visit the HPV section of our website.
Heliobacter pylori is a common bacterium that grows in the stomach. It is estimated that approximately 8 to 10 million people in Canada have H.pylori in their stomach (23-29%); however, only 1.2% of men and 0.8% of women will develop stomach cancer2. Therefore, while the number of people with the infection is high, most people with H. pylori do not develop any medical conditions due to the infection. However, H. pylori is a necessary, but not the only, cause of adenocarcinoma, the most common stomach cancer, accounting for 95% of cases3. It is also associated with a higher risk of MALT lymphoma of the stomach and potentially pancreatic and colorectal cancers, although there is not enough evidence to definitively say it is a risk factor. Interestingly, H. pylori may also have a protective effect against certain conditions, including gastroesophageal reflux disease and esophageal carcinoma4.
Hepatitis B and C
Liver cancer due to Hepatitis B and C is more common in developing countries, likely due to the higher rates of infection. In North America, primary liver cancer account for less than 1% of all cancers, while in other countries it can account for up to 50% of cancers. The incidence of Hepatitis C in Canada is 33.7 per 100,000 5 and 0.6 per 100,000 for Hepatitis B6. Approximately 2-6% of those with chronic Hepatitis C infection will develop liver cancer per year7. Hepatitis B can be prevented through vaccination, and both strains of Hepatitis can be prevented by not sharing needles and by using a barrier method of contraception.
1. Canadian Cancer Society. (2015). Human papillomavirus (HPV). Retrieved July 2015 from http://www.cancer.ca/en/cancer-information/cancer-101/what-is-a-risk-factor/viruses-bacteria-and-other-infectious-agents/hpv/?region=on#HPV_and_cancer
2. Canadian Digestive Health Foundation. (2008). H. Pylori. Retrieved July 2015 from http://www.cdhf.ca/en/statistics#13
3. Canadian Cancer Society (2015). H. Pylori and Cancer. Retrieved July 2015 from http://www.cancer.ca/en/cancer-information/cancer-101/what-is-a-risk-factor/viruses-bacteria-and-other-infectious-agents/h-pylori/?region=on
4. Hung, I.F.N. and Wong, B. C. Y. (2009) Assessing the risks and benefits of treating helicobacter pylori infection. Therapeutic Advances in Gastroenterology 2: 141-147.
5. Public Health Agency of Canada, Hep C & STI, surveillance and epi section. Epidemiology of acute hepatitis C infection in Canada: results from the enhanced hepatitis strain surveillance system (EHSSS) 2009.
6. Public Health Agency of Canada (2011) Hepatitis B – Get the Facts. Retrieved July 2015 from http://www.phac-aspc.gc.ca/hcai-iamss/bbp-pts/hepatitis/hep_b-eng.php
7. De Oliveira Andrade, L.J., D’Oliveira, A. J., Carvalho Melo, R., Conrado de Souza, E., Alves Costa Silva, C., and Parana, R. (2009). Association between hepatitis C and hepatocellular carcinoma. Journal of Global Infectious Diseases 1: 33-37.