Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome
Acquired immunodeficiency syndrome (AIDS) is a condition in which the immune system has lost the ability to defend the body against infection and certain cancers. It is caused by infection with human immunodeficiency virus (HIV).
The cause of AIDS is infection with HIV. HIV is a member of the family of viruses called retroviruses. This type of virus enters human cells and becomes incorporated into the cell's genes (i.e., DNA). Once the infection has occurred, the body cannot rid itself of the virus. The effect of the virus on the immune system leads to AIDS.
HIV/AIDS affects people of all ages and racial/ethnic backgrounds. Usually, infants and children acquire the infection from the mother during pregnancy, delivery, or breastfeeding. The most common mode of transmission for teens and adults is sexual contact. Currently, the largest number of HIV-infected people lives in Africa, India, and Southeast Asia. In the United States, homosexual men and injecting drug users have the highest prevalence of infection. However, adolescents and women, particularly those of African-American and Hispanic background, have the highest rates of new infections.
Casual, classroom, or household contact with an HIV-infected person poses no risk. Transmission cannot occur from sharing dishes, towels, or bathroom facilities. Saliva, urine, and stool are not contagious unless there is visible blood in the fluid.
HIV is transmitted through contact with infected semen or cervical secretions. People who have sexual contact with an infected person are at risk of acquiring the infection. The virus can be transmitted by both heterosexual and homosexual contact. Men and women, adults and teenagers can become infected with HIV.
HIV is transmitted from mother to infant during pregnancy, delivery, and breastfeeding. An infected woman who does not receive treatment during pregnancy has a 25% to 30% chance of passing the virus on to her baby. With treatment, the chance of having an infected baby can be reduced to 1%.
HIV is transmitted through contact with infected blood or body fluids contaminated with visible blood. Donated blood is screened for HIV so there is almost no risk of an infection from blood transfusion products. However, people who use injection drugs sometimes share their injection equipment. If an HIV-infected person shares a needle or other injection equipment, the virus can be transmitted to the other people. A health care professional who is exposed to blood from an infected person has a risk of being infected with HIV. This risk is greatest when a contaminated sharp instrument penetrates the skin. There also is a small risk of infection when blood splashes into the eye or the mouth of the worker. There is no risk of infection with blood contact to intact skin (i.e., skin without cuts, scratches, or a rash). Under usual circumstances, there is no risk of transmission of HIV from a health care professional to a patient. However, all people should handle blood and bloody body secretions carefully.
HIV infection, without treatment, causes a progressive dysfunction of the immune system. When the immune system is defective, the body cannot defend itself against infections. HIV infects immune cells that are critical components of the immune system, particularly helper T lymphocytes (T4 cells). When the cells are infected with HIV, they do not function normally, and some cells are destroyed.
Teens and adults may have symptoms in the first two to six weeks after the initial infection with HIV (acute primary infection). The most common symptoms of the primary infection are fever, fatigue, muscle aches, headache, sore throat, and swollen lymph nodes (glands in the neck, under the arms, and in the groin). These symptoms are not specific to HIV infection since many viral infections cause similar symptoms. Some other symptoms more particular to primary HIV infection are mouth ulcers, a rash, and meningitis. However, even these symptoms do not prove HIV infection because they can occur with other infections. Some people have no symptoms after the acute infection. The symptoms of the primary infection resolve without treatment. Most people do not seek medical attention, and they are not aware that they have acquired HIV.
After the primary infection, most people infected with HIV have no symptoms in the early stages of the disease. For adults and adolescents, progression of the disease usually occurs several years after the primary infection. About 30% of infants infected at birth will have disease progression within 12 to 18 months of life.
When the disease progresses, common first symptoms include enlargement of the lymph nodes, liver, and/or spleen; poor growth; frequent minor infections, such as ear infections and sinusitis; cold sores that do not heal; thrush or diaper rash that persists despite treatment; shingles; night sweats; and recurrent fever. When the disease reaches advanced stages, most patients have weight loss; infections of the lungs, blood stream, bones, joints, intestines, and eyes; and certain cancers. Some people develop neurologic symptoms manifested by developmental delay in children and by memory loss and dementia in teens and adults.
The most commonly used diagnostic test for HIV infection detects antibodies to HIV in the blood. The body makes antibodies as a part of the immune defense against infections. If antibodies against HIV are present (a "positive" test), this indicates that the person is infected with HIV. This is why infected people are called "HIV positive."
The antibody test is done in two parts. The first part is called an ELISA. Occasionally, a person will test positive on an ELISA even though they are not HIV infected. Therefore, a positive ELISA test must have a confirmatory test done on the same blood sample showing that the antibodies are truly specific for HIV. A negative ELISA indicates that the person is not infected and usually does not require a follow-up test.
In some patients, antibody tests are not reliable. In this case, tests that directly detect the virus are used. The most commonly used tests detect the virus genetic material (DNA or RNA) or protein (p24 antigen) in the blood. Virus tests are used to diagnose HIV infection in infants born to HIV-infected mothers. Antibody tests on the baby are not reliable until after 18 months of age because all mothers will pass antibodies to their babies, but not all mothers will pass the virus. In order to determine if the infant is infected, tests to detect the virus in the baby's blood are performed. The majority of infected infants will have the virus detected by three to four months of life. Uninfected infants will have negative tests for the virus (even though their antibody test is positive).
Direct virus testing also is used for adults and teenagers who may have been recently exposed to HIV. The virus tests are positive about 10 to 14 days before the antibody tests are positive. Using the direct virus test permits an earlier diagnosis of infection.
Recently, many new medications have been developed to treat HIV infection. These medications are called anti-retroviral drugs, and they inhibit the replication or reproduction of the virus. Effective treatment requires a combination of several different anti-retroviral medications, taken by mouth, one to three times a day. The amount of virus in the blood and the number of helper T cells are monitored closely to determine whether the medications are effective. Although there is no cure for HIV/AIDS, with effective treatment, infected people may live for years without disease progression.
The complications of HIV infection are primarily related to immune dysfunction. Immune dysfunction leads to infection with other bacteria, viruses, or fungi. Medications can be taken daily or weekly to prevent these infections. In some patients, HIV causes abnormal function of the heart, bone marrow, brain, muscles, intestines, liver, and pancreas.
The most important method to prevent HIV infection is to avoid exposure by sexual contact. Abstinence is the only certain way to avoid sexual exposure to HIV. The risk of transmission can be greatly reduced by the correct use of condoms during sexual contact. Individuals who do have sexual contact should limit their number of partners and use condoms correctly every time they have sexual contact.
Sharing contaminated needles can transmit HIV. Injection drug users should not share injection equipment. Children should be taught to avoid contact with other people's blood. They also should avoid sharing sharp personal objects (e.g., razors, body-piercing equipment), which may be contaminated by blood and have not been properly sterilized. When caring for a bleeding wound, a thick layer of paper or cloth should be used to reduce the chances of contact with the blood.
Over 95% of infections passed from mother to infant can be prevented if the mother and infant receive treatment during pregnancy, labor, and the first weeks after birth. All women should be offered testing for HIV during pregnancy so they can receive the preventative treatments if they are HIV positive.
Research on the treatment and prevention of HIV infection is very active. The areas of most intense interest are the development of a vaccine to prevent infection, the development of improved anti-retroviral medications, and studies to understand how the body's immune defenses against HIV infection can be enhanced.
Sponsor: The Francois-Xavier Bagnoud Center, University of Medicine and Dentistry of New Jersey, The National Pediatric and Family HIV Resource Center (NPHRC). This Web site includes extensive information about HIV that is related to children and youth.
This Web site includes information about HIV that is written at a child's level.
This Web site includes information about HIV that is both focused on youth and written in youth-friendly terms.
About the Author
Dr. McFarland is the medical director and co-founder of the Children's Hospital Immunodeficiency Program (CHIP) in Denver, CO. CHIP provides comprehensive health care to infants, children, adolescents, young adults and pregnant women infected or affected by HIV.
Dr. McFarland is a member of the National Institutes of Health sponsored Pediatric AIDS Clinical Trial Group and is active in basic and clinical HIV research. She is board certified in Pediatric Infectious Diseases and a faculty member at the University of Colorado Health Sciences Center.
She received her MD degree from Duke University School of Medicine and her pediatric and subspecialty training from the University of Colorado Health Sciences Center.
Copyright 2012 Elizabeth J. McFarland, M.D., All Rights Reserved
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