Do Viruses Cause Cancer?

Whether it may be genetic or environmental, there are many factors that can lead to cancer. One of these factors could be infections, which can be caused by bacteria, fungi, and/or viruses.  

Viruses insert themselves inside our bodies and alter our otherwise functioning genes, making us sick. Viruses can only thrive when they infect a person or host, and when they do, they quickly find cells to intercept a cells machinery — from mitochondria to ribosomes — to replicate themselves enough to take over our system before our immune system kicks in. 

Some viruses can cause cancer in a variety of ways with direct or indirect strategies. The direct method, oncoviruses (cancer-causing viruses), infect normal cells and slip some of their genes into the cells’ DNA. This causes the cells to produce a few abnormal proteins. If the cells acquire additional gene mutations, or if the individual has a weakened immune system, the cells can turn cancerous.  

A viral infection can also cause tissue to become inflamed as the immune system tries to quell the infection. Such inflammation, persisting for years or even decades, increases the chances that tissue will become cancerous. 

There are seven viruses that are connected to specific types of cancer.

Human papillomavirus (HPV) 

Human papillomavirus (HPVs) refers to a group of more than 150 related viruses that are spread by contact.  At least a dozen of them are known to cause cancer, including cervical cancer and some types of head and neck cancer. Certain HPVs also have a role in penile, anal, vaginal, and vulvar cancers.  

While infection with one or more HPVs is very common, cancers arising from these infections are rare and are more likely to occur in people with long-lasting infections of certain high-risk types of HPV.  

Vaccination against the three main cancer-causing types of HPV can prevent more than 90% of HPV-related cancers and is available for children and young adults. 

Epstein-Barr virus 

Epstein-Barr virus (EBV) is a type of herpes virus that causes mononucleosis. Infection with EBV increases a person’s risk of nasopharyngeal cancer, certain types of fast-growing lymphomas, and possibly some cases of Hodgkin lymphoma and stomach cancer.  

There are many viruses that already live inside us without us realizing it. EBV, for example, has already infected most of the global population, and for many of us, it simply lies dormant in our bodies until it is triggered. Triggers may include stress, hormonal changes, or other illnesses that hinder our immune system.  

There are no medicines to eliminate EBV from the body and no vaccines to prevent it, but EBV infection doesn’t cause serious problems in most people. 

Hepatitis B and hepatitis C viruses (HBV and HBC) 

Hepatitis B and Hepatitis C viruses (HBV and HBC) cause hepatitis, an infection of the liver. These viruses can be spread by sharing needles, unprotected sex, or blood transfusions (although this is rare in the U.S. as donated blood is tested for them). Long-term infection with either HBV or HBC can increase a person’s likelihood of developing liver cancer.  

There is a vaccine to prevent HBV infection, but not for HCV. In the United States, the HBV vaccine is recommended for all children and for adults up to age 59. 

Human immunodeficiency virus (HIV) 

Human immunodeficiency virus (HIV) is the virus responsible for AIDS, which doesn’t cause cancer directly, but by undermining the immune system, it can make some cancers more likely. HIV can be spread through semen, vaginal fluids, blood, and breast milk from an HIV-infected person. HIV infection has been linked to a higher risk of: 

• Kaposi sarcoma 
• Cervical cancer 
• Certain kinds of non-Hodgkin lymphoma and Hodgkin lymphoma 
• Colon and rectal cancers   
• Liver cancers 
• Oral cancers 
• Lung cancers  

While there is currently no vaccine to fight against HIV, individuals can protect themselves by using contraceptives during sex. Other therapies, such as anti-HIV drugs, can help reduce the chance of HIV-related cancers for those who are already infected.  

Human herpes virus 8 (HHV-8) 

Human herpes virus 8 (HHV-8) can be detected in nearly all tumors in patients with Kaposi sarcoma, a cancer that forms in cells lining blood and lymph vessels. The virus is transmitted through sex and, research suggests, through blood and saliva as well. Fewer than 10% of people in the United States are infected with the virus, which does not cause disease in most healthy individuals.

While research is underway for the development of a new vaccine for HHV-8, safe sex practices are the best way to reduce your risk.  

Human T-lymphotrophic virus-1 (HTLV-1) 

Human T-lymphotrophic virus-1 (HTLV-1) has been linked to a form of lymphocytic leukemia and to a form of non-Hodgkin lymphoma called adult T-cell leukemia/lymphoma.

Found mostly in Japan, the Caribbean, central Africa, and parts of South America, HTLV-1 is a retrovirus, whose genetic code is written in RNA rather than DNA. This type of virus can use their RNA genome to mimic unhealthy DNA inside our cells that causes permanent damage and becomes transmissible between a mother and child.   

Merkel cell polyomavirus (MCV) 

Merkel cell polyomavirus (MCV) has been found in tissue samples of a rare, aggressive type of skin cancer called Merkel cell carcinoma. This kind of carcinoma is highly responsive to immunotherapy with a PD-1 antibody. Most people infected with MCV experience no symptoms, but a few go on to develop Merkel cell carcinoma. 

About the Medical Reviewer

Dr. Wucherpfennig received his MD in 1986 and his PhD in 1987 from the University of Goettingen, Germany. He completed research fellowships at Brigham and Women's Hospital and the Department of Molecular and Cellular Biology, Harvard University. In 1995, he joined DFCI, where he is principally involved in basic laboratory research that focuses on T cell immunology and the role of T cells in cancer immunology.