6 Viruses That Can Lead to Cancer

A Minority of Infections Become Cancerous

No one type of virus causes cancer. The six different viruses that can cause cancer come from different virus families, have varied genomes, and have different life cycles.  

Overall, infection with any of these viruses is very common. Fortunately, only a minority of people infected with these viruses ever go on to develop cancer. And if cancer were to develop, it would take years or even decades to take hold. Furthermore, viruses on their own are insufficient to cause cancer and must also accompany immunosuppression, somatic mutations, genetic predisposition, and exposure to carcinogens.

Here are six types of viruses that cause cancer (aka human tumor viruses):

Hepatitis C

Hepatitis C is an RNA virus. It causes both acute and chronic hepatitis. Chronic infection with hepatitis C causes cirrhosis or scarring of the liver. In 1 to 2 percent of those infected, this cirrhosis can eventually lead to hepatocellular (liver) cancer. Hepatitis C has also been linked to non-Hodgkin's lymphoma.

Although researchers have yet to develop a vaccine for hepatitis C, effective treatments for the disease exist, including Sovaldi and Harvoni.

Hepatitis B

Whereas hepatitis C is an RNA virus, hepatitis B is a DNA virus. Despite being a different class of virus, hepatitis B causes infection with a clinical course similar to hepatitis C: acute and chronic hepatitis, cirrhosis, and hepatocellular cancer. 

Hepatocellular cancer is an aggressive cancer that kills a year or two after infection. While treatment for hepatocellular cancer is possible—a small number of people may undergo surgical resection of the liver or liver transplant—most patients either have cancer that is too advanced for surgery, or their underlying liver disease (cirrhosis) makes them a poor candidate for surgery.

Fortunately, we have a vaccine for hepatitis B, and getting vaccinated can help reduce your risk of liver cancer.

Human Papilloma Virus (HPV)

Human papilloma virus (HPV) is a small DNA virus that causes genital warts. Persistent infection with high-risk subtypes of HPV can result in cervical cancer. Moreover, persistent HPV infection has also been implicated in the development of other types of cancer, including head and neck tumors, skin cancers in immunosuppressed patients (think AIDS), and anal, vulvar, and penile cancers.

Fortunately, thanks to the PAP smear, we have highly effective early screening for cervical cancer. The HPV vaccine—a significant recent medical advance—is also highly effective at preventing cancers related to this virus when given in adolescence. Evidence is emerging it's likely to be effective at older ages as well.

Human T Lymphocyte Virus Type 1 (HTLV-1)

HTLV-1 is an RNA retrovirus. Across the world, 5 to 25 million people are infected with this virus; however, only a minority (5 percent) develop symptoms. HTLV-1 has a tropism (or attraction) to CD4 cells, white blood cells that play an important role in the immune system. Twenty to thirty years after infection with HTLV-1, adult T-cell leukemia can develop.  

Chemotherapy can initially be used to treat adult T-cell leukemia and results in short-term remission followed by quick recurrence of the disease. The median survival time after development of adult T-cell leukemia is 8 months.

Epstein-Barr Virus

Epstein-Barr Virus (EBV) is a ubiquitous virus that we're all familiar with by another name—it causes mononucleosis. Although the vast majority of people have likely been exposed to EBV at some point, most infections are subclinical, with a minority of people developing clinical disease.

EBV has been linked to a variety of cancers, including B- and T-cell lymphomas, leiomyosarcomas, nasopharyngeal carcinomas, Hodgkin’s disease, and post-transplant lymphoproliferative disease.

HHV-8 or Kaposi Sarcoma Herpesvirus

In 1994, HHV-8, or Kaposi sarcoma herpesvirus, was implicated in the development of Kaposi's sarcoma, a cancer which causes skin and mouth lesions (sores) in those with AIDS. HHV-8 is also associated with primary effusion lymphoma, a rare type of non-Hodgkin lymphoma. However, in those with stronger immune systems, HHV-8 rarely induces malignancies.

Future Therapeutic Directions for Human Tumor Viruses

Novel therapeutic approaches to cancer caused by human tumor viruses focus on viral gene products that are specific to tumor cells caused by the virus. By developing treatments that specifically target cells which have been infected by viruses, future treatment options can spare the body's healthy cells. Currently, treatments like chemotherapy and radiotherapy kill all cells, which explains their nasty and severe adverse effects.

Currently, the best way to prevent cancer secondary to human tumor viruses (however rare) is to prevent exposure to human tumor viruses themselves. Although some of these viruses are ubiquitous, we can prevent exposure to certain of these viruses like hepatitis B and C. Hepatitis B and HPV vaccinations are also available.