Lymphoma is the term for a group of related blood cancers. Research has found that certain viruses may be risk factors for lymphoma. The two main types of lymphoma are Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL). There are also several different lymphoma subtypes.
Not everyone with lymphoma will have had a viral infection. As risk factors, viral infections don’t necessarily cause lymphoma but instead are associated with an increased risk of developing different types of lymphoma. Viruses connected to lymphoma include:
These viruses are thought to play a role in the development of different types of lymphoma through the cellular processes that occur in the body when infected with a virus. As viruses affect the body differently, different viruses work in distinct ways to influence the development of lymphoma.
With lymphoma, genetic mutations occur in the lymphocytes (white blood cells) and cause these cells to divide and multiply in abnormal ways. As these genetically mutated, unhealthy cells start to outnumber the healthy cells in the lymph nodes and lymph system, lymphoma may develop.
Viral infections affect the body’s immune system and risk of diseases (and cancer such as lymphoma) in several different ways. Some infections increase the activity of the immune system and lymphocyte production. When the production of lymphocytes occurs beyond a normal pace, there is a greater chance that genetic mutations may lead to lymphoma.
Some viral infections affect lymphocytes directly by altering their DNA, increasing the risk of lymphoma. Viral infections can also weaken the immune system. With a weakened immune system, it is much more difficult for the body to fight off infections, including those linked to lymphoma.
EBV causes mononucleosis (“mono”) and is associated with a higher risk of HL. EBV infection is common — about 90 percent of people in the world will contract EBV at some point in their lives. The virus spreads through saliva and by sharing food, drinks, or utensils.
About 30 percent of people with HL carry the Epstein-Barr virus. EBV is associated with specific subtypes of NHL, including:
Many more people have EBV than HL, meaning EBV is not the sole factor in determining who does and who doesn’t develop HL.
EBV-related lymphoma is more common in people who have a suppressed immune system, such as those who have HIV or who have had a stem cell or organ transplant within the past year. Although scientists are still exploring the exact details, it is believed that EBV infects B cells (cells that usually fight off bacteria and viruses) and creates genetic mutations in these cells that could contribute to the development of lymphomas.
HIV weakens the immune system and makes the body more susceptible to infection or disease. According to the Leukemia & Lymphoma Society, people with HIV are at an increased risk of developing HL. HIV is also a risk factor for different types of NHL such as:
HIV increases a person’s chances of developing lymphoma by infecting a type of lymphocyte called helper T cells. Helper T cells work by activating other cells that are a part of the immune system, so if these cells do not work properly, the immune system cannot effectively fight off infections.
HCV spreads through blood and can cause liver cancer. HCV has also been associated with lymphomas including:
A study in the Journal of the American Medical Association from 2007 found that for veterans in the United States, HCV infection increased the risk of NHL by 20 percent to 30 percent. It is believed that HCV infection is connected to lymphoma through lymphoproliferation, a process in which lymphocytes reproduce in an uncontrollable manner that can cause lymphoma.
Another viral infection associated with lymphoma is HTLV-1. This virus is less common in the United States and is connected to less than 1 percent of lymphomas. HTLV-1 is more common in Japan, the Caribbean, Africa, and South America.
HTLV-1 is spread through blood and is thought to be related to the development of adult T-cell lymphoma. The virus works by interrupting the natural cell growth and division processes of lymphocytes, which could result in lymphoma.
HHV-8, also called Kaposi sarcoma-associated herpesvirus, is a virus that can affect the functioning of lymphocytes. The virus has been connected to a rare kind of lymphoma called primary effusion lymphoma, which mostly affects young people who are immunosuppressed or have an HIV infection.
HHV-8 is less common in the United States compared to areas such as sub-Saharan Africa and regions of South and Central America. Similar to other viral infections, HHV-8 can lead to the proliferation (increase in the number of cells) of lymphocytes.
Although certain viruses have been connected to different types of lymphoma, not everyone infected with these viruses will develop lymphoma. It is also possible to have lymphoma that is not associated with a virus at all. Scientists believe lymphoma develops from an interaction between various factors, including environmental, lifestyle, and genetic factors, that ultimately influence who and who does not develop lymphoma.
Aside from viral infections, other risk factors include:
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