Oncogenic Infections



Oncogenic (on-ko-JEH-nik) infections are infections that may increase a persons risk of developing a certain type or types of cancer.

KEYWORDS

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Burkitt's lymphoma

Epstein-Ban virus

Helicobacter pylori

Hepatitis

Human lymphotrophic virus

Human papillomavirus

What Are Oncogenic Infections?

Cancer often is linked to lifestyle choices (such as smoking), a person's genetic * makeup, and environmental influences. Researchers now have begun to make connections between the development of certain types of cancer and specific viral, bacterial, and parasitic infections. These infections are referred to as oncogenic, or tumor-producing, infections.

Oncogenic viruses transfer their genetic material to other cells and then remain in the body for a long time as a latent infection (meaning that they are 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-steen BAR) 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 others.

Specific Oncogenic Infections

There are several infections that 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. Sexually transmitted HPVs are linked to the development of cervical * , penile * , and anal * cancer. (Anal and penile cancers are rare in the United States.)

* genetic (uh-NEH-tik) refers to heredity and the ways in which genes control the development and maintenance of organisms.

* 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.

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-zhuh), or precancerous cells in the cervix. This condition can lead to cancer if it is left untreated. 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 5 million new infections diagnosed each year. There is no cure for HPV, and treatment is aimed at controlling the infection.

A child with Burkitt's lymphoma, a type of tumor first discovered in Africa. The African form of Burkitt's lymphoma is strongly associated with early childhood infection by the Epstein-Barr virus. Custom Medical Stock Photo, Inc.
A child with Burkitt's lymphoma, a type of tumor first discovered in Africa. The African form of Burkitt's lymphoma is strongly associated with early childhood infection by the Epstein-Barr virus.
Custom Medical Stock Photo, Inc.

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 fluid from the mouth and nose 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's disease and non-Hodgkin's 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.

Hepatitis B and C virus (HBV and HCV) infections primarily affect the liver. They are spread through contact with infected blood, such as through the sharing of needles (including needles for tattooing, body piercing, and drug use). HBV also can spread through contact with the body fluids of an infected person during sexual intercourse. Some people with hepatitis have no symptoms at all, but in others the infection eventually can result in liver cancer or liver damage from cirrhosis (sir-O-sis), a condition in which liver cells die and are replaced with scar tissue. Because HBV and HCV infections generally are chronic, the viruses are present in the body for a long time and can do significant damage. As the body tries to overcome this damage, new cells are created at a faster rate, increasing the risk of cell mutation * and liver cancer. Hepatitis is treated with injections of interferon (in-ter-FEER-on) alpha-2b, a drug that strengthens the immune system to fight the virus. HBV infection can be prevented by vaccination against the infection.

* Pap smear is a common diagnostic test used to look for cancerous cells in the tissue of the cervix.

* mononucleosis (mah-no-nu-klee-O-sls) is an Infectious Illness caused by a virus that often leads to 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.

It is now known that the Helicobacter pylori * bacterium causes 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-deh-no-kar-sin-O-muh). Gastric cancer has been diagnosed more often

Oncogenic Infections
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 * and lymphoma primarily in people from Japan, the southern Pacific islands, the Caribbean, parts of central Asia, and central and western Africa. Infection with the virus often occurs at birth, but it can remain inactive for years and sometimes decades before cancer develops. The virus usually is spread through contact with contaminated blood, from prolonged exposure to an infected sexual partner, or from mother to child through breast milk. The earlier a person contracts the infection, the higher the risk of lymphoma. This virus is related to the human immunodeficiency (ih-myoo-no-dih-FIH-shen-see) virus (HIV), the cause of acquired immunodeficiency syndrome (AIDS). HIV itself is an oncogenic virus that has been linked to several types of cancer.

* lymphatic (lim-FAH-tik) system is a 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-fair-in-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-THEE-lee-um). the sheets of cells that line body surfaces, such as the insides of hollow organs and cavities.

* lymph (LIMF) nodes are small, bean-shaped masses of tissue that contain 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 (HEEL-ih-ko-bak-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, also known as peptic ulcer disease.

* duodenol (do-uh-DEE-nul) refers to the upper part of the small intestine.

* ulcer is an open sore on the skin or the lining of a hollow body organ, such as the stomach or intestine. It 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.

How Can People Protect Themselves from Oncogenic Infections?

Exposure to oncogenic infections does not mean that a person will get cancer. Many people contract such infections and never get cancer. Scientists believe that many factors play a role in the development of cancer and think that these infectious agents increase the risk only for some people. Avoiding exposure to these infections can lower the risk of certain types of cancer. People can avoid HPV infection, as well as human lymphotrophic virus type 1 and HIV 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 wise to avoid poorly sanitized needles for tattoos, piercing, or 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.

* intravenous (in-tra-VEE-nus) 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.

See also
AIDS and HIV Infection
Helicobacter Pylori Infection (Peptic Ulcer Disease)
Hepatitis, Infectious
Mononucleosis, Infectious
Sexually Transmitted Diseases
Warts

Resources

Organization

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC offers information about many infectious diseases, including H. pylori and HPV infections, at its website.
Telephone 800-311-3435
http://www.cdc.gov

Website

KidsHealth.org . KidsHealth is a website created by the medical experts of the Nemours Foundation and is devoted to issues of children's health. It contains articles on a variety of health topics, including Epstein-Barr virus, HPV, and hepatitis.
http://www.KidsHealth.org



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