Can a virus cause cancer?

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on June 13, 2022.

Yes, it’s true—some viruses may cause cancer. When a virus enters the body, it reproduces, making copies of itself. Viruses invade specific cells and use those cells to help them replicate, often by changing their genetic makeup—either their DNA or RNA.

These genetic changes may make cells more vulnerable to becoming cancerous. Different viruses cause cancer in various parts of the body, and some are associated with higher cancer risk than others.

Vaccines are available for some of these viruses—and may help protect against infection as well as prevent certain virus-associated cancers.

Human papillomaviruses (HPVs)

There are more than 150 types of HPVs, and some may cause cancer. HPV is associated with cancer of the anus, vagina, vulva, penis, mouth and throat, but it’s most well-known for causing cervical cancer. Almost all cases of cervical cancer are due to a few types of HPV—deemed high-risk HPV types.

Cancer-causing HPV types usually spread through sexual activity. Transmission may occur with vaginal, oral and anal sex. If you’re sexually active, it’s likely that you have contracted—or will contract—HPV during your lifetime. HPV infections typically don’t show symptoms, but sometimes they cause genital warts.

While most HPV infections don’t lead to cancer, it’s important to avoid the possibility. Luckily, there are options available to do so.

Given to children and young adults, HPV vaccines may guard against more than 90 percent of HPV-related cancers, according to the American Cancer Society (ACS). HPV vaccines are typically administered to young people before they become sexually active. These vaccines work by preventing individuals from being infected with high-risk HPV types that could lead to cancer.

Experts recommend that children get an HPV vaccine at age 11 or 12, according to the National Cancer Institute. Adults up to age 45 and children as young as 9 are also eligible.

There are also screening tests available for cervical cancer, including those caused by HPV, to detect early signs. The Pap test is a commonly used screening tool in the United States that looks for abnormal cells in the cervix that may become cancerous. If abnormal cells are found, they may be removed before that happens.

Epstein-Barr virus (EBV)

EBV is commonly known for causing mononucleosis (or “mono”), but it may also cause cancers of the nose and throat and some types of lymphoma, such as Burkitt lymphoma and Hodgkin lymphoma.

Mono is sometimes called the “kissing disease” because contact with saliva is the primary means of EBV transmission. Kissing, coughing, sneezing and sharing toothbrushes or utensils are all potential ways that EBV may transfer from person to person. EBV is a lifelong infection. It remains in particular blood cells even if you never had any symptoms when you were infected.

While EBV can’t be cured with drugs nor prevented by vaccines, the risk of developing severe problems related to EBV is low. This is a common infection, but cancers caused by EBV are rare.

Hepatitis B virus (HBV) and hepatitis C virus (HCV)

If the Hepatitis B or C virus infects the liver, it may cause long-term infections that may result in cancer.

HBV and HCV are transmitted through contact with blood. They spread from person to person through shared needles, blood transfusions, childbirth (from mother to baby) and unprotected sex.

These viruses raise the risk of liver cancer when they cause chronic liver infections.

Adults who contract HBV may experience short-term, flu-like symptoms and jaundice (yellowing of the skin and eyes), but HBV infections are unlikely to become chronic. Young children are more at risk of chronic HBV infections.

The HBV vaccine is recommended for all children and for adults who may be more at risk by sexual exposure or exposure to blood (such as health-care workers, for example), according to the Centers for Disease Control and Prevention (CDC). Many people get vaccinated as infants.

HCV rarely shows symptoms, but it’s more likely to cause chronic liver infections that may result in an elevated risk of liver cancer. About 3.2 million people in the United States have a chronic HCV infection and most of them don’t know it, according to the ACS.

There’s no vaccine to protect against HCV, but the CDC recommends that all U.S. adults get screened for hepatitis C at some point after age 18. Pregnant women and other select groups with known risk factors should also be screened. Routine periodic testing is recommended in people who inject drugs and share needles or have received hemodialysis. For those who test positive, treatment options are available to reduce liver damage and limit cancer risk. HBV infections may also be treated with drugs.

Human immunodeficiency virus (HIV)

HIV is the virus behind acquired immune deficiency syndrome (AIDS). HIV doesn’t directly cause cancer, but its damaging effect on the immune system may make people more vulnerable to other infections that lead to cancer. For example, someone with HIV may be unable to fight off an HPV infection, leaving them at risk of cancer.

HIV infections elevate the risk of several cancers, including:

HIV spreads through bodily fluids such as semen, blood and breast milk. HIV may spread from person to person through unprotected sex or sharing needles.

HIV infections may not start causing symptoms for many years. While there’s no vaccine for HIV, you may protect yourself by avoiding unprotected sex and sharing needles. There are medications available to treat people living with HIV, as well as medicines that lower the risk of infection in individuals exposed to HIV.

Kaposi sarcoma-associated herpesvirus (KSHV)

KSHV, or human herpesvirus-8 (HHV-8), is a type of herpes virus that may sometimes cause a rare cancer called Kaposi sarcoma. Even more rarely, KSHV has been linked to other cancers, such as primary effusion lymphoma (PEL).

Fewer than 10 percent of people in the U.S. are estimated to be infected with KSHV, according to the ACS. It appears to spread in different ways in various regions. In the United States and Northern Europe, where it’s relatively rare, KSHV is primarily spread through sexual contact.

KSHV is often symptomless. KSHV seems to cause problems and lead to cancer in individuals with a weakened immune system, such as people living with HIV. While there are no vaccines to prevent the disease, and no drugs that treat it, individuals may protect themselves by avoiding oral-anal contact, especially men who have sex with men.

Human T-cell lymphotropic virus type 1 (HTLV-1)

HTLV-1 is a rare virus in the United States that may cause a type of cancer called adult T-cell leukemia/lymphoma (ATL). Fewer than 1 percent of people nationwide are estimated to have HTLV-1, according to the ACS, but the virus is more common in other areas such as southern Japan, the Caribbean, central Africa, and parts of South America. For those with HTLV-1, the risk of developing ATL is about 5 percent. This cancer may take many years after infection to develop.

HTLV-1 doesn’t usually cause symptoms. Someone with HTLV-1 may spread the virus through blood, such as by sharing needles or sexual contact. Mothers who have HTLV-1 may also pass the virus to their children through breastfeeding.

There is no vaccine to prevent infection with this virus and no treatment for already infected individuals.

Merkel cell polyomavirus (MCV)

MCV is a common virus that may cause an aggressive type of skin cancer called Merkel cell carcinoma, though it rarely does. The risk of MCV-related cancer is high in older adults and people who are immunocompromised, such as those living with HIV.

Most people contract MCV during their lifetime, usually in early childhood. The virus seems to spread by having skin-to-skin contact or touching an infected surface, according to the NCI. It usually doesn’t present symptoms.

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