How infections cause cancer?

How infections cause cancer?

Cancer can happen to anyone. However, there are certain risk factors that increase the likelihood of getting cancer.  You might be aware of a few of them e.g. tobacco, air pollution, etc. Nonetheless, not many know that certain infections can cause cancer as well. In fact, infective agents were the first factors implicated in cancer causation.

Approximately 20% of human cancers are caused by infectious agents and as such, they rank second only to tobacco as a potentially preventable cause in humans.  Cancer of cervix in females and cancer of liver & stomach in males are the most common cancers caused by an infectious agent.

According to an article published on 25th July 2016 in the Lancet Global Health, of 14 million new cancer cases in 2012, 15.4% were attributable to carcinogenic infections. Two-thirds of infection-attributable cancers occurred in less developed countries. Cervical cancer in India is the second most common cancer in females and the majority of cases are attributed to human papillomavirus. Preventing infections in cancer patients can save them from serious health complications.

Which infections cause cancer and the infectious agents responsible for them:


Cancer Infections 
Cancer of cervix Human papilloma virus (HPV)
Cancer of liver Hepatitis B (HBV) and Hepatitis C virus (HCV)
Cancer of throat Human papilloma virus (HPV)
Cancer of anal canal Human papilloma virus (HPV)
Cancer of stomach Helicobacter pylori bacteria
Cancer of nasopharynx (region situated behind the nose) Epstein Barr virus (EBV)
Burkitt lymphoma  (a kind of cancer of lymph nodes ) Epstein Barr virus (EBV)
Kaposi's sarcoma Human herpesvirus type 8 (HHV-8)
Urinary bladder cancer Schistosoma haematobium ( kind of parasite)

How do infections cause cancer?

  1. Infections cause a chronic inflammatory state which has harmful effects over cells. This over a period of time causes changes in DNA of the cells, which initiates cancer pathways.

  2. Some infections directly affect DNA especially HPV virus which gets integrated into DNA and causes cancer. 

Preventing infections in cancer patients :

The important thing about infections associated with cancer is- if you get rid of infections or prevent them in the first place then the likelihood of cancers caused by them goes down. Various strategies are:

  1. Vaccination: In India, we have vaccines available for hepatitis B, Hepatitis C, and HPV which reduces cancer risk. HPV vaccines can now be given to females as low as 9 years of age. This has drastically reduced the risk of cervical cancer in countries where HPV vaccination has been successfully implemented. Many states in India are now implementing it under their vaccination program.

  2. Improvement in personnel hygiene.

  3. Use of barrier contraception during sexual intercourse.

These preventable causes of cancer and simple measures go a long way to reduce incidences of deadly cancers.


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