The impact of certain viruses on the body can cause cells to lose control and transform into malignant tumors. Research indicates that over one hundred thousand cancer cases worldwide are attributed to viruses.
At least seven types of viruses are known to be direct or indirect causes of cancer, according to Live Science. These include: human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), Epstein-Barr virus (EBV), herpes virus, human T-cell lymphotropic virus, and Merkel cell polyomavirus.
Illustration of cancer cells. (Photo: MD Anderson Cancer Center).
Additionally, the immunodeficiency virus (HIV) increases cancer risk by “opening the door” for cancer-causing viruses to enter the body.
Estimates from 2012 showed that viruses accounted for 10% of the 1.4 million cancer cases globally. Dr. Jay Berzofsky, a senior researcher at the National Cancer Institute, explains that viruses can cause cancer through both direct and indirect mechanisms. Each type of virus has its own way of inducing cancer.
Direct Mechanisms
One of the most well-known cancer-causing viruses is HPV. Each year, HPV leads to 37,000 new cancer cases. It is known to contribute to the development of cervical, anal, oropharyngeal, penile, vaginal, and vulvar cancers.
Some HPV types promote cancer by transforming healthy cells into tumor cells. HPV produces harmful proteins that disable the natural tumor suppression system of normal cells. “This allows tumors to grow uncontrollably,” says Dr. Harrys Torres, an infectious disease professor at the MD Anderson Cancer Center, University of Texas, USA.
There are over 200 types of HPV, but only 12 types are strongly associated with cancer.
HPV virus causes 37,000 new cancer cases each year, according to Live Science. (Photo: Shutterstock).
EBV and human T-cell lymphotropic virus also cause cancer directly. They operate through different genetic mechanisms but lead to the same outcome: cancer cells proliferate rapidly and evade the body’s defense system.
Many factors determine whether these viruses can cause cancer. For both HPV and EBV, certain strains have a higher oncogenic potential than others.
Individuals with weakened immune systems are also more susceptible to cancer due to viruses. External factors can increase the likelihood of tumor development, such as mutations or exposure to carcinogens.
Indirect Mechanisms
Viruses can also cause cancer indirectly. HBV and HCV are two strains of viruses that lead to chronic infections resulting in prolonged inflammation, cirrhosis, or liver scarring. “Chronic inflammation has a high rate of leading to cancer,” Dr. Berzofsky states.
When the body tries to repair damage caused by HBV and HCV by producing new liver cells, those cells can mutate and develop into cancer. HCV is also associated with non-Hodgkin lymphoma, a type of lymphatic cancer caused by the virus continuously stimulating the immune system.
Meanwhile, HIV increases the risk of cancer development through indirect mechanisms. This virus does not cause chronic inflammation but weakens the immune system. As a result, the body becomes more vulnerable to attacks by direct cancer-causing viruses.
