Oncogenic (on-ko-JEH-nik) infections are those that may increase a person's risk for developing a certain type or types of cancer.
Cancer often is linked to lifestyle choices (such as smoking), a person's genetic * makeup, and environmental influences. However, connections between the development of certain types of cancer and specific viral, bacterial, and parasitic infections also exist. These infections are referred to as oncogenic, or tumor-producing, infections.
An oncogenic virus * transfers its genetic material to other cells and then remains in the body for a long time as a latent infection (meaning dormant, or inactive, but not dead) or as a chronic (KRAH-nik) infection (meaning that the infection continues for a long time). For example, Epstein-Barr (EP-stine BAHR) virus remains in the body for life, occasionally flaring up and being subdued by the body's immune system * . Chronic infections such as hepatitis (heh-puh-TIE-tis) B or C often damage the body slowly, over many years.
Another characteristic of oncogenic infections is that they seem to encourage cells to reproduce at an unusually fast rate, which may damage the genetic material in those cells. Additional factors, such as smoking or exposure to other carcinogens * , may be needed to trigger the final change of a normal cell into a cancer cell. These exposures, along with each person's individual genetic makeup, may explain why cancer develops in some people who have had oncogenic infections but not in others.
Several infections have been linked to the development of cancer. Human papillomavirus (pah-pih-LO-muh-vy-rus), or HPV, is a family of more than 70 different types of viruses that can produce warts * on various parts of the body. Some strains * of HPV are spread sexually and cause genital * warts. Certain sexually transmitted HPVs are linked to the development of cervical * , penile * , and anal * cancer. (Anal and penile cancers are rare in the United States.)
According to the American Cancer Society, the most important risk factor for a woman in the development of cervical cancer is HPV infection. HPV is found in 90 percent of cervical cancer cases. Its presence may make a woman more likely to have cervical dysplasia (SIR-vih-kul dis-PLAY-zha), or precancerous cells in the cervix. This condition can lead to cancer if it is left untreated. Just having one of the oncogenic strains of HPV, however, does not mean cancer will eventually develop. Early discovery and treatment can lessen a woman's risk of cervical cancer, and doctors advise women diagnosed with HPV to have frequent Pap smears * . HPV is the most common sexually transmitted disease in the United States, with five million new infections diagnosed each year. Although there is no cure for HPV, there are treatment options aimed at controlling the infection.
Epstein-Barr virus (EBV) is commonly known as the virus that causes infectious mononucleosis * . Up to 95 percent of adults in the United States have been infected with the virus by the time they are 40 years old. EBV is transmitted through contact with saliva of someone who is infected. Children who contract EBV rarely have symptoms, and when they do, the symptoms typically are the same as those of common viral infections. When adolescents or adults are infected with EBV, they can have infectious mononucleosis.
EBV remains in the body, primarily in the lymphocytes * , for the rest of a person's life. It is dormant for much of the time, although it occasionally flares up without causing any real harm. People with weakened immune systems are at particular risk that EBV will flare up and cause illness. EBV is associated primarily with the development of Hodgkin disease and non-Hodgkin lymphoma * (both cancers of the lymphatic system * ), nasopharyngeal * carcinoma * , and Burkitt's lymphoma, a rare cancer arising in the lymph nodes * that is a common type of childhood tumor in some parts of the world, primarily central Africa.
The Helicobacter pylori * bacterium is linked to most cases of gastric (stomach) and duodenal * ulcers * . The infection can be treated with antibiotics. People infected with H. pylori are at higher risk of stomach cancers, such as gastric lymphoma and adenocarcinoma (ah-dehno-kar-sih-NO-muh). Gastric cancer has been diagnosed more often in countries where H. pylori infection is common, such as China and Colombia, and it is believed that the combination of infection, diet, and other factors contributes to these cancers. The bacteria may spread through contact with feces (FEE-seez), or bowel movements, found in contaminated water sources or on hands that have not been washed thoroughly.
Human lymphotrophic (lim-fo-TRO-fik) virus type 1 is a virus that has been linked to the development of certain types of leukemia *
Exposure to oncogenic infections does not mean that individuals will get cancer. Many people contract such infections and never get cancer. Many factors play a role in the development of cancer, and these infectious agents increase the risk only for some people. Nonetheless, avoiding exposure to these infections can lower the risk of certain types of cancer.
People can avoid HIV infection, as well as human lymphotrophic virus type 1 and HPV infection, by limiting the number of their sexual partners and practicing abstinence (not having sex) or safe sex. To prevent hepatitis B and C, it is essential to avoid poorly sanitized needles for tattoos, piercing, or illegal intravenous * drug use. Thorough hand-washing, particularly after using a bathroom or changing a diaper, can lessen the risk of infection with H. pylori. It is almost impossible to avoid exposure to Epstein-Barr virus.
HBV infection can also be prevented by vaccination * against the infection. Research has demonstrated that the HPV vaccine can prevent more than 70 percent of all cervical cancers. The American Congress of Obstetricians and Gynecologists and the federal Advisory Committee on Immunization Practices recommend that girls receive this three-immunization series prior to becoming sexually active. The target age range for administration is age 11 or 12, although it can be given at any point between ages 9 and 26.
See also AIDS and HIV Infection • Cancer: Overview • Helicobacter pylori Infection • Hepatitis • Human Papillomavirus (HPV) • Lymphoma • Mononucleosis, Infectious • Sexually Transmitted Infections (STIs): Overview • Warts
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Ajiro, Masahiko, and Zhi-Ming Zheng. “Oncogenes and RNA Splicing of Human Tumor Viruses.” Emerging Microbes & Infections 3. (September 3, 2014). http://www.nature.com/emi/journal/v3/n9/full/emi201462a.html (accessed October 23, 2015).
Krueger, Hans, Gavin Stuart, Richard Gallagher, Dan Williams, and Jon Kerner. HPV and Other Infectious Agents in Cancer: Opportunities for Prevention and Public Health. Oxford, UK: Oxford University Press, 2010.
American Cancer Society. “Viruses That Can Lead to Cancer.” http://www.cancer.org/cancer/cancercauses/othercarcinogens/infectiousagents/infectiousagentsandcancer/infectious-agents-and-cancer-viruses (accessed May 12, 2016).
OncoLink. http://www.oncolink.org (accessed May 12, 2016).
American Cancer Society. 250 Williams St. NW, Atlanta, GA 30303. Toll-free: 800-227-2345. Website: http://www.cancer.org (accessed October 23, 2015).
American Congress of Obstetricians and Gynecologists. 409 12th St. SW, Washington, DC 20024. Toll-free: 800-673-8444. Website: http://www.acog.org (accessed November 21, 2015).
Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA, 30329. Toll-free: 800-311-3435. Website: http://www.cdc.gov (accessed October 23, 2015).
National Cancer Institute. BG 9609 MSC 9760, 9609 Medical Center Dr., Bethesda, MD, 20892. Toll-free: 800-422-6237. Website: http://www.cancer.gov (accessed October 23, 2015).
* genetic (juh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.
* virus (VY-rus) is a tiny infectious agent that can cause infectious diseases. A virus can only reproduce within the cells it infects.
* immune system (im-YOON SIStem) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.
* carcinogens (kar-SIH-no-jenz) are substances or agents that can cause cancer.
* warts are small, hard growths on the skin or inner linings of the body that are caused by a type of virus.
* strains are various subtypes of organisms, such as viruses or bacteria.
* genital (JEH-nih-tul) refers to the external sexual organs.
* cervical refers to the cervix (SIR-viks), the lower, narrow end of the uterus that opens into the vagina.
* penile (PEE-nile) refers to the penis, the external male sexual organ.
* anal refers to the anus, the opening at the end of the digestive system through which waste leaves the body.
* Pap smear is a common diagnostic test used to look for cancerous cells in the tissue of the cervix.
* mononucleosis (mah-no-nuklee-O-sis) is an infectious illness caused by a virus with symptoms that typically include fever, sore throat, swollen glands, and tiredness.
* lymphocytes (LIM-fo-sites) are white blood cells, which play a part in the body's immune system, particularly the production of antibodies and other substances to fight infection.
* lymphoma (lim-FO-muh) refers to a cancerous tumor of lymphocytes, cells that normally help the body fight infection.
* lymphatic system (lim-FAH tik) is the system that contains lymph nodes and a network of channels that carry fluid and cells of the immune system through the body.
* nasopharyngeal (nay-zo-fairin-JEE-ul) refers to the nose and pharynx (FAIR-inks), or throat.
* carcinoma (kar-sih-NO-muh) is a cancerous tumor that arises in the epithelium (eh-puh-THEElee-um), the sheets of cells that line body surfaces, such as the insides of hollow organs and cavities.
* lymph nodes (LIMF) are small, bean-shaped masses of tissue containing immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
* mutation (myoo-TAY-shun) is a change in an organism's gene or genes.
* Helicobacter pylori (HEELih-kobak-ter pie-LOR-eye) is a bacterium that causes inflammation and ulcers, or sores, in the lining of the stomach and the upper part of the small intestine.
* duodenal (do-uh-DEE-nul) refers to the upper part of the small intestine.
* ulcers are open sores on the skin or the lining of a hollow body organ, such as the stomach or intestine. They may or may not be painful.
* leukemia (loo-KEE-me-uh) is a form of cancer characterized by the body's uncontrolled production of abnormal white blood cells.
* intravenous (in-tra-VEE-nus), or IV, means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.
* vaccination (vak-sih-NAY-shun), also called immunization, is giving, usually by an injection, a preparation of killed or weakened germs, or a part of a germ or product it produces, to prevent or lessen the severity of the disease caused by that germ.