Viruses are a type of pathogen (germs or tiny microorganism that causes disease) that cause viral infections. Most viral infections, like the common cold, are short-lived and mild. However, there are times when viruses cause more substantial, long-term harm, including complications such as cancer. 

Research estimates that 10% of cancer cases worldwide are caused by viruses. The majority of these affect people in developing countries.

Many virus-associated cancers can take years to become symptomatic, which makes it difficult to know this percentage with certainty.

This article reviews how viruses can cause cancer, which types are known to cause cancer, prevention, and screening.

How a Virus Causes Cancer

All viruses are composed of genetic material (which may be DNA or RNA) enclosed in a protein coat. Viruses have the ability to invade a “host,” such as a human or animal.

Sometimes this invasion causes cancer through the oncogenesis. Oncogenesis is a multistep process where healthy cells turn into cancer cells.

There are several ways that a virus can cause cancer, including:

  • Genetic damage or mutations (errors in genetic material)Altering the immune system so that it is less able to fight off cancer cells (which could have initially developed due to something other than the virus)Chronic inflammationDisrupting the body’s normal regulation of cell division

Viruses That Cause Cancer

Several different viruses are associated with cancer. Both DNA and RNA viruses can cause cancer. Typically, a virus causes a specific type or a few types of cancer due to how it interacts with the body.

Whenever cells divide, there is a risk that a genetic mutation will take place. Some viruses lead to inflammation or tissue damage that triggers increased cell division—which leads to a greater chance that mutations will take place, eventually leading to cancer.

HTLV-1 is a retrovirus (similar to HIV) that causes adult human T-cell leukemia/lymphoma.

HHV-8 (also known as Kaposi sarcoma herpes virus, KSHV) can cause Kaposi’s sarcoma.

Merkel cell polyomavirus (McPyV) can cause Merkel cell carcinoma, a form of skin cancer. The virus is very common in the population as a whole, but cancer associated with the McPyV virus is uncommon.

Human Papillomavirus (HPV)

The human papillomavirus (HPV) is a sexually transmitted virus affecting nearly 80 million Americans. It is the most common type of sexually transmitted infection.

Importance of Screenings and Prevention

For those diagnosed with a virus associated with cancer, you should keep up with recommended screenings and preventative strategies. Regular screening can help you avoid the potentially severe consequences of cancer with potential links to that virus.

There are currently over one hundred known strains of HPV, but only a tiny portion of these are thought to cause cancer. The strains of HPV most commonly associated with cancer include HPV 16 and HPV 18.

The detection of the DNA of HPV virus is found in:

  • Cervical cancer: 90%Vulvar cancer: 69%Anal cancer: 91%Vaginal cancer: 75%Penile cancer: 63%Head and Neck cancer: 30% of mouth cancers and 20% of throat cancers

In some other cancers, the data is less certain. For example, HPV is linked to lung cancer, but it’s not known if HPV contributes to the development of lung cancer.

Hepatitis B (HBV)

Viral hepatitis B (HBV) infections are highly contagious and are spread through the transmission of blood, semen, and other bodily fluids from one person to another. Means of exposure include:

HPV Vaccination

Vaccination for HPV—a shot that protects against HPV 16 and HPV 18—is available for children between the ages of 11 and 12, and can be given starting at age 9 and as old as age 26.

  • Sharing of needles or drug injecting equipment (most common)Unprotected sexMother to infant transmission during childbirth

Most people recover from an acute hepatitis B infection, but some people go on to develop a chronic hepatitis B infection. Chronic infections are more common among those who contract the disease in early childhood and those with no symptoms.

Infection with Hepatitis B virus (HBV) increases the risk of developing liver cancer. Liver cancer occurs more often among those with chronic hepatitis B.

Hepatitis C (HCV)

Hepatitis C (HCV) infection increases the risk of developing liver cancer and non-Hodkin lymphoma. 

Hepatitis B Vaccination

Most children born since the 1980s have been immunized against hepatitis B. Adults who have not been immunized may discuss this option with their doctors.

The virus is a bloodborne infection. This means it is spread through infected blood and body fluids. Most people get HCV sharing needles or other drug injecting equipment. It can also be transmitted through unprotected sex, and mothers can pass it to their unborn babies.

Early disease is often asymptomatic (no signs or symptoms). When symptoms are apparent, they include:

Hepatitis C Prevelance

Chronic hepatitis C affects nearly 180 million people world wide.

  • Abdominal painClay-colored stoolDark urineFeverFatigueJoint painJaundice (yellowing of the skin or eyes)NauseaPoor appetiteVomiting

For some, HCV is a short-lived virus, but about 50% become chronic (long-term) infections. As the immune system attacks the virus over time, liver fibrosis (scarring) develops, eventually leading to cirrhosis (cell death). This chronic inflammation can lead to liver cancer.

Epstein-Barr Virus

The Epstein-Barr virus most commonly causes mononucleosis but is also known to cause nasopharyngeal carcinoma and gastric carcinoma.

Is There a Hepatitis C Vaccination?

While research is ongoing, there is not currently a vaccination for hepatitis C (HCV). However, there is a blood test that can detect HCV. It is recommended that adults born between 1945 and 1965 or who are at high-risk be tested for the disease.

Additionally, this virus is linked with the development of several different types of lymphoma, including:

  • Posttransplant lymphoma: Some people develop lymphoma after an organ transplant, many of which are related to Epstein-Barr virus infections.
  • HIV-associated lymphoma: Over 90% of HIV-associated lymphoma is related to EBV.
  • Burkitt’s lymphoma: In Africa, Burkitt’s lymphoma is responsible for over half of all childhood cancers, and nearly all of these are linked to the Epstein-Barr virus.
  • Hodgkin’s lymphoma: It’s thought that the Epstein-Barr virus plays a role in 30 to 50% of cases of Hodgkin’s disease in the U.S.

Human Immunodeficiency Virus (HIV)

HIV suppresses the immune system and is linked to cancer in several ways. Types of cancer that HIV could cause include:

  • Non-Hodgkin lymphoma (NHL) (most common cancer in people with HIV)
  • Hodgkin lymphoma
  • Primary CNS lymphoma
  • Leukemia
  • Kaposi’s sarcoma
  • Cervical cancer
  • Lung cancer
  • Anal cancer
  • Liver cancer

The immunosuppression caused by HIV can predispose people with the disease to cancer because immune cells do not effectively fight cancer cells when a person is infected with HIV. Because HIV weakens the immune system, the cancer cells caused by the Epstein Barr virus or any other mutation can multiply and survive—causing a person to develop severe illness from cancer.

HIV infection also causes certain immune cells (B cells) to multiply, increasing the risk of overproduction and mutation, leading to B cell cancers.

Prevention

Many of the viruses that can lead to cancer are passed from person to person. Other pathogens (germs) such as bacteria and parasites are also linked with cancer development.

Prevention is a key component of avoiding cancer as a complication of any infection. Prevention strategies include:

  • Vaccinations: Get vaccinated when possible: There are vaccinations for some of these viruses, including HPV and HBV. For others, such as hepatitis C (HCV) and HIV, vaccinations are not available
  • Avoiding risky behaviors: Avoid behaviors such as sharing needles or unprotected sex
  • Screening and testing: Keep up with recommended screening and testing when available.
  • Boost your immune system: Practice healthy habits like eating right, managing stress, getting rest, and exercising to keep your immune system strong. A suppressed immune system can raise the risk of some viral-induced cancers.

Summary

Viruses are usually short-term but can have long-term complications such as cancer. Approximately 10% of cancer cases worldwide are caused by viruses. 

Research

Prevention of cancer caused by viruses is a developing area of research—especially the emergence of prevention through vaccines. Additionally, researchers are working on strategies that use viruses to fight cancer.

Viral infections lead to cancer when it damages, mutates, or disrupts cell growth or division. Viruses can also cause inflammation or alter the immune system, making it more difficult to fight cancer cells.

There are several viruses associated with cancer, including human papillomavirus (HPV), human immunodeficiency syndrome (HIV), hepatitis B and C, Epstein-Barr, and a few more.

Prevention involves vaccinations, safe sex, and not sharing needles or drug injection equipment. Viruses can break through even when you try your best to prevent them. If this is the case, ask your healthcare provider about ways to screen or monitor for possible complications.

A Word From Verywell

The thought of a virus leading to cancer can be scary. It’s important to note that most viruses do not cause cancer. Even when viruses produce cancer-associated genetic mutations, a healthy immune system removes most of the damaged cells. 

If you’ve had a virus that can lead to specific cancer, talk to your healthcare provider about screening and monitoring. Early detection and treatment are extremely beneficial.

Frequently Asked Questions

  • Is cancer viral or bacterial?
  • Cancer causes a body’s cells to mutate, multiply, or grow abnormally. Cancer is not defined as a viral or bacterial infection. However, specific viral or bacterial infections can cause certain types of cancer.
  • Are all cancers caused by viruses?
  • No, not all cancers are caused by viruses. Research suggests that about 10% of cancers worldwide can be attributed to cancer.

Cancer causes a body’s cells to mutate, multiply, or grow abnormally. Cancer is not defined as a viral or bacterial infection. However, specific viral or bacterial infections can cause certain types of cancer.

No, not all cancers are caused by viruses. Research suggests that about 10% of cancers worldwide can be attributed to cancer.