Scientists haven’t found a clear cause of multiple myeloma, but they’ve identified several risk factors, including exposure to certain viruses.

While some viral infections are linked to a higher risk of myeloma, there’s no proof that these viruses directly cause myeloma. Viruses are known to cause some cancers and increase the risk of others, so researchers are studying this potential link.

Having a viral infection doesn’t mean you’ll develop myeloma. However, understanding the link can help you and your healthcare team assess your risk factors.

How Can Viruses Be a Risk Factor for Cancer?

Viruses may affect myeloma development in different ways. They can change how cells function, potentially increasing cancer risk. For example, viruses may raise inflammation levels, weaken the immune system, or disrupt signals that normally control cell growth. All of these effects could contribute to cancer development.

Some people with multiple myeloma have no known risk factors. Others may have risk factors they can’t change, like race, age, or family history.

However, vaccines and other preventive measures can protect against cancer-causing viruses. If you think you’ve been exposed to a virus linked to multiple myeloma, contact your healthcare provider. They can test for the virus and prescribe antiviral treatment to reduce symptoms and complications.

Multiple Myeloma, MGUS, and the Immune System

Multiple myeloma is a cancer that starts in abnormal white blood cells in the bone marrow, also known as plasma B cells.

Healthy plasma cells make proteins called antibodies. Antibodies help fight infections like viruses. In multiple myeloma, these cells don’t work correctly and produce abnormal antibodies called monoclonal proteins (or M proteins). Over time, M proteins build up and damage vital organs like the kidneys and bones.

Multiple myeloma often starts with a condition called monoclonal gammopathy of undetermined significance (MGUS). People with MGUS also have a buildup of M proteins, and their genetics may increase their risk of developing multiple myeloma. However, most people with MGUS never develop myeloma and may not have symptoms or need treatment. Many don’t even know they have MGUS unless they’re tested for it.

MGUS can run in families or develop due to gene mutations caused by factors like pesticide exposure or viruses.

Viral Infections and Multiple Myeloma

It’s unclear why plasma cells stop working properly in multiple myeloma, but viral infections may play a role. Viruses are infectious diseases that can alter DNA and disrupt healthy cell growth, potentially leading to cancer. Viruses can also weaken the immune system, making it harder for the body to fight off bacterial and fungal infections.

Scientists aren’t sure whether viral infections are a definite risk factor for myeloma. It’s likely that a combination of factors increases the risk of the disease. However, growing evidence suggests that certain viruses may increase the chances of developing both MGUS and multiple myeloma.

Viruses that may be linked to myeloma include:

• Human immunodeficiency virus (HIV)
• Hepatitis
• Some herpes viruses

Human Immunodeficiency Virus

HIV weakens the immune system, making it harder for the body to fight infections and diseases. There is no cure for HIV, and it remains in the body for life. HIV is spread through activities considered “high-risk,” like having unprotected sex or sharing needles. People with HIV have a higher risk of certain cancers like Kaposi sarcoma, lymphoma and leukemia and cancers of the lung, liver, cervix, anus, and throat.

Research shows that MGUS and multiple myeloma are associated with HIV. People who have HIV and multiple myeloma are more likely to develop myeloma at a younger age. They’re also more likely to have aggressive forms of multiple myeloma that progress faster.

Hepatitis Viruses

Hepatitis means “inflammation of the liver.” While it can be caused by genetics or heavy alcohol use, some forms of hepatitis are caused by viruses. These include hepatitis A, B, C, D, and E. People can get viral hepatitis from contaminated food or water or through contact with infected blood or bodily fluids.

Research shows that people with hepatitis B (HBV) and hepatitis C (HCV) have higher rates of MGUS and multiple myeloma. In addition, antiviral therapy has been shown to improve multiple myeloma outcomes in people with HBV and HCV. Early treatment for these viruses could help lower the risk of multiple myeloma or reduce its severity in those who develop it.

Herpes Viruses

Herpes simplex virus (herpes) is a group of common infections. Herpes is usually spread through skin-to-skin contact with someone who has the virus. There’s no cure for herpes, but you can get treatment to control the symptoms. Symptoms include painful blisters around the mouth or genitals, depending on the type of herpes virus.

Some herpes viruses have been studied as possible triggers for multiple myeloma. Human herpesvirus-8 (HHV-8) — also called Kaposi sarcoma-associated herpes virus (KSHV) — is a type of herpes that has been linked to certain cancers, including Kaposi sarcoma and lymphoma. HHV-8 is a common infection that’s spread through saliva and doesn’t usually cause symptoms or cancer. While older studies suggested a link between HHV-8 and multiple myeloma, recent evidence doesn’t strongly support this connection. Future research may clarify whether this link exists.

A 2024 study also reported that severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection may be a risk factor for developing myeloma due to its effects on the immune system.

Other Multiple Myeloma Risk Factors

Scientists believe viral infections are only one possible risk factor for multiple myeloma. Other genetic and lifestyle factors may also lead to an increased risk of multiple myeloma. However, having these risk factors doesn’t mean someone will definitely develop multiple myeloma.

The risk of multiple myeloma is higher for Black people, older adults, and men. Other risk factors include:

• Exposure to certain pesticides or other chemicals
• A family history of multiple myeloma or MGUS
• Having MGUS

If you’re concerned about your risk factors for multiple myeloma, including viral infections, talk to your oncology team. Early testing and treatment can make a big difference, especially if a viral infection or cancer is caught in its early stages.

Talk With Others Who Understand

MyMyelomaTeam is the social network for people with multiple myeloma. On MyMyelomaTeam, more than 28,000 members come together to ask questions, give advice, and share their stories with others who understand life with multiple myeloma.

Do you know whether you’ve been exposed to any of the viruses linked to multiple myeloma? Share your thoughts in the comments below, or start a discussion by posting on your Activities page.