How Infectious Diseases Cause Cancer

Up to 30% of all cancers worldwide have been linked to infectious diseases, caused by microbes such as viruses, bacteria, and parasites. Next to cigarette smoking, microbial are second in causes of human cancers that can be prevented.

How do infectious microbes cause cancer?

Cancer is characterized by uncontrolled growth of cells in the body. Microbes can cause this to happen in three main ways:

  1. Many infectious microbes cause the body’s immune system to initiate a cascade of events leading to inflammation. While inflammation in the body occurs in order to control infections, some of the infectious-disease-fighting molecules made by white blood cells can damage a person’s own DNA, proteins, and cell surfaces. During a persistent infection, the inflammation can become chronic, leading to continual damage and accumulation of genetic mutations that can contribute to the development of cancer.
  1. Several microbes, particularly viruses, invade human cells and directly interact with their DNA. This interaction can lead to activation of genes that promote the growth of tumors, or it can lead to inactivation of genes that prevent the development of tumors.
  2. Some microbes, such as HIV, which can reduce the effectiveness of a person’s immune system, can also decrease the efficiency with which the immune system recognizes cancer cells or cells infected with cancer-causing viruses.

What can we do about cancer-causing infectious agents?

Here’s the good news:Since many infectious diseases, including those implicated in cancer, are preventable, either through drugs, vaccines, and even cultural practices, it is feasible to lower the risks for these cancers. For example, vaccines have now been developed for hepatitis B virus, which is a major cause of liver cancer, and for human papillomavirus (HPV), the primary cause of cervical cancer.

Continuing research into the role of infectious diseases in cancer will undoubtedly uncover new ways to prevent this deadly disease.


Howley PM and DeMasi J. Infectious Agents and Cancer. In: The Molecular Basis of Cancer, 3rd ed. ©2008 Saunders, An Imprint of Elsevier.

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