Infectious agents and cancer

Several cancers have been attributed to infectious agents. It is estimated that approximately 18% of all cancers worldwide are caused by infectious agents. 26% of these are in developing countries and 8% in developed countries. These figures and discrepancies between the developed and developing worlds point to differences in disease prevalence, either due to sanitary conditions or shortage of vaccines. Infectious agents can be classified as indirect or direct carcinogens. Indirect carcinogenic agents are those that cause chronic infection and thus chronic inflammation, which then leads to the advent of cancer. Examples of these include, Helicobacter pylori infection that is the an attributing factor to a majority of stomach/gastric cancers, as well as chronic hepatitis B and C infections that are causally linked to a majority of liver cancers.  On the other hand, direct carcinogenic agents are those that can incorporate oncogenes into the cell’s genome. Examples of these are human papillomavirus that causes a majority of cervical cancers, as well as in some cases, penile cancer, vaginal cancer and genital warts; Epstein-Barr virus linked to a majority of Naso-pharengeal carcinomas and human herpes virus-8 linked to Kaposi’s sarcoma. This list grows every day. The good news is this: most of these infections, and thus the advent of several cancers, can be prevented by vaccination.

Related articles

• Parkin, DM. 2006. The global health burden of infection-associated cancers in the year 2002. Int J Cancer. 118:3030.
• Campbell, K. 2006. The infectious causes of cancer. Nurs Times. 102(33):28.
• FDA approves Gardasil to prevent genital warts in boys (ctv.ca)
• FDA Approves Merck’s Gardasil for Boys (abcnews.go.com)