The human immunodeficiency virus (HIV) is a virus that causes AIDS (acquired immune deficiency syndrome). HIV primarily attacks the immune defense system, making the patient extremely vulnerable to opportunistic infections. Opportunistic infections occur in individuals who have weakened immune systems.
HIV primarily infects and destroys immune cells called CD4 T-cells. Healthy individuals have a CD4 cell count between 600 and 1,200 cells per microliter of blood. HIV patients have less than 600 CD4 cells per microliter of blood. AIDS patients have the greatest risk of developing opportunistic infections that may be fatal.
HIV is transmitted from person to person via bodily fluids including blood, semen, vaginal secretions, and breast milk. Therefore, it can be transmitted through sexual contact with an infected person, by sharing needles/syringes with someone who is infected, through breastfeeding, during vaginal birth or, less commonly (and rare in countries where blood is screened for HIV antibodies), through transfusions with infected blood. HIV has been found in saliva and tears in very low quantities and concentrations in some AIDS patients. However, contact with saliva, tears, or sweat has never been shown to result in HIV transmission.
The most common type of HIV worldwide is called HIV-1. It is easily transmitted and is the cause of most HIV/AIDS infections around the world. HIV-1 has several subtypes (A through H and O), which have different geographic distributions but produce AIDS similarly. The second type, called HIV-2, is much less common and less virulent.
Currently, there is no cure for HIV/AIDS. Patients may receive anti-HIV drugs called antiretrovirals. These drugs help suppress the virus, which subsequently helps boost the immune system. Although these drugs may help patients live longer lives, they do not reduce the risk of transmitting the disease to someone else.
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Experts have recently concluded that HIV originated in chimpanzees in Africa. Evidence suggests that the simian form of HIV, known as SIV, entered the human species when monkeys bit humans or humans consumed monkey meat or brains.
1959: While the first HIV outbreak was reported in 1981, it was recently confirmed that a man from Africa died from complications of HIV in 1959.
1982: The U.S. Centers for Disease Control and Prevention (CDC) coined the term AIDS (acquired immune deficiency syndrome) for the newly discovered syndrome. About 1,600 cases were diagnosed one year after the first outbreak in 1981, resulting in close to 700 deaths.
1983: Thirty-three other countries had confirmed cases of the syndrome. Researchers at the Pasteur Institute in France isolated a virus that they believed was related to the outbreak of AIDS. However, a year later the U.S. government announced that Dr. Robert Gallo isolated a virus that he also claimed was responsible for AIDS.
1985: Researchers confirmed that HTLV-III and the Pasteur retrovirus were the same virus. However, Gallo was credited with its discovery. An international committee of scientists renamed the virus HIV, and the first test for HIV was approved in 1985.
1987: The U.S. Food and Drug Administration (FDA) approved the first anti-HIV drug, called zidovudine (Retrovir®). By the end of 1987, there were 71,000 confirmed cases of AIDS, resulting in over 40,000 deaths.
1990: Congress enacted the Ryan White Care Act, which provided government sponsored funds for the care of HIV infected people.
1996: Antiretrovirals called protease inhibitors were introduced.
The results of the AIDS Clinical Trials Group study 076 suggested that taking zidovudine during pregnancy and at the time of delivery drastically reduced transmission of the virus from mother to child.
South African president Thabo Mbeki publicly questioned the efficacy of HIV medications and doubted that HIV causes AIDS. In response, the international scientific community issued the Durban Declaration at the International Aids Conference, offering proof that HIV and AIDS are connected.
The first fusion inhibitor, called enfuvirtide (Fuzeon®), was made available to HIV patients.
2003: At the end of 2003, an estimated 1,039,000 to 1,185,000 people in the United States were living with HIV/AIDS.
2004: Two new combination drugs, emtricitabine/tenofovir disoproxil fumarate (Truvada®) and abacavir sulfate/lamivudine
Epzicom®, were made available to the public. Two new protease inhibitors, atazanavir sulfate (Reyataz®) and fosamprenavir calcium (Lexiva®), were also released in 2004.
2005: In 2005, 4.9 million people were newly diagnosed with HIV. An estimated 40.3 million people were living with HIV/AIDS worldwide.
2006: India surpassed South Africa as having the world's largest HIV population. HIV infection rates in the United States remain fairly steady, while other STDs are on the rise.
As of January 2006, the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) estimate that AIDS has killed more than 25 million people since 1981.
HIV is transmitted from person to person via bodily fluids including blood, semen, vaginal secretions, and breast milk. Individuals who have other sexually transmitted diseases are more susceptible to the virus.
HIV is different from many other viruses because it reproduces much quicker and has a high mutation rate. When HIV reproduces, different strains (types) of the virus emerge. Mutations (changes) occur almost every time a new copy of the virus is produced. Therefore, many types of HIV can be produced in a single person in one day. That is why HIV patients receive different combinations of antiretrovirals to suppress the virus.
HIV can infect and kill many different types of cells in the body, but the primary targets are immune cells called CD4 T-cells. The CD4 T-cells are white blood cells that help coordinate the immune system's response to infection and disease. These cells have a molecule called CD4 on their surfaces, which allow the cells to detect foreign substances, including viruses that enter the body. HIV binds to the receptors on the CD4 cell wall and enters the cell. Once inside the cell, HIV begins replicating, killing the cell.
Patients can transmit the virus to others during all stages of infection. The first stage of HIV, known as the primary or acute infection, is the most infectious stage of the disease, and it typically lasts several weeks. During this phase, the virus replicates rapidly, which leads to an abundance of the virus in the bloodstream and a drastic decline in the number of CD4 T-cells.
The CD8 T-cells, which kill abnormal or infected body cells, are then activated to destroy HIV-infected body cells and antibodies are produced.
The next stage, called clinical latency, may last anywhere from two weeks to 20 years. During this phase, HIV is active in the lymph nodes where large amounts of the virus become trapped. The surrounding tissues, which contain high levels of CD4 T-cells, may also become infected. The virus accumulates in infected cells and in the blood as free virus. Patients generally do not experience symptoms during this stage.
As the virus continues to weaken the immune system, patients eventually become more susceptible to infections. Patients may experience infections, such as pneumonia or tuberculosis, before the onset of AIDS.
The term AIDS (acquired immune deficiency syndrome) refers to the most advanced stage of HIV infection. Individuals who have AIDS have less than 200 CD4 T-cells per microliter of blood, making them extremely vulnerable to opportunistic infections that may be fatal. These infections occur in individuals who have weakened immune systems.
Some infections, including Pneumocystis jiroveci pneumonia (formerly called Pneumocystis carinii pneumonia, PCP), are considered AIDS-defining illnesses. This means that once a patient develops the infection, their condition has progressed to AIDS.
The U.S. Centers for Disease Control and Prevention (CDC) tracks the spread of HIV and AIDS in the United States.
During the mid-to-late 1990s, advances in HIV treatment slowed the progression of HIV infection to AIDS. This consequently led to decreases in AIDS deaths. According to the CDC, the number of AIDS deaths continues to decline, with an 8% decrease from 2000 through 2004. However, the number of AIDS diagnoses increased 8% during that period as well.
Advanced treatments can also be attributed to the 30% increase in the number of people in the United States who are living with AIDS. From 2000 to 2004, the estimated number of people living with AIDS increased from 320,177 to 415,193, according to the CDC. This is because new treatments help HIV/AIDS patients to live longer lives.
General: Race and ethnicity by themselves do not increase or decrease an individual's risk of HIV infection. However, certain people are more likely to face challenges associated with the risk for HIV infection, such as lack of awareness of HIV status, substance abuse, or socioeconomic issues.
African Americans accounted for 20,965 (49%) of the 42,514 estimated AIDS cases diagnosed in the United States. The rate of AIDS diagnoses for African American adults and adolescents was 10 times higher than the rate of whites, and almost three times higher than the rate of Latinos. In addition, the rate of AIDS diagnoses for African American women was 23 times higher than the rate of white women. The rate of AIDS diagnoses for African American men was eight times higher than the rate of white men, according to the CDC.
In 2004, Latinos accounted for 20% (8,672) of the 42,514 new diagnoses in the United States, according to the CDC. Most Latino men acquired infections after exposure to the virus through sexual contact with other men, followed by injection drug use, and heterosexual contact. Most Latino women acquired infections after exposure to the virus through heterosexual contact, followed by injection drug use. HIV testing rates were higher among Latinos than any other race or ethnicity except African Americans. According to the CDC, in 2004, about 50% of Hispanics between the ages of 15 and 44 were tested, and 18% had been tested during the past year.
After the initial outbreak of HIV, few women were diagnosed with the virus. Today, women account for more than a quarter of all new HIV/AIDS diagnoses in the United States. In 2004, an estimated 93,566 women were living with AIDS, making up 23% of the estimated 415,193 people living with AIDS in the United States.
Youth (13-24 years old): In the United States, it is estimated that 50% of the 40,000 new HIV infections each year occur in people younger than 25 and 25% occur in people younger than 21. HIV/AIDS ranks as the sixth-leading cause of death among individuals ages 15-24 in the United States, with the number of AIDS cases reported each year in that age group increasing by 417% from 1981 through 1994.
Injection-drug users: Since the AIDS epidemic began, injection drug use (IDU) with illegal drugs has directly and indirectly accounted for more than one-third of AIDS cases in the United States. In the year 2000, out of the 42,156 new cases of AIDS reported, 11,635 were IDU-associated.
Injection drug use is more common among racial and ethnic minorities in the United States, which makes them more likely to acquire HIV through IDU. In 2000, IDU accounted for 26% of all AIDS cases among African American adults and 31% among Hispanic adults and adolescents, compared to 19% of all cases among white adults and adolescents.
Homosexuals: Men who have sex with men (MSM) accounted for 70% of all estimated HIV infections among male adults and adolescents in 2004 in the United States, according to the CDC. Although the number of HIV diagnoses for MSM decreased during the 1980s and 1990s, the number increased by 8% from 2003 through 2004. According to the CDC, it is unknown whether this increase is because more people are getting tested for HIV or because more patients are becoming infected with HIV.
Bodily fluids: HIV is transmitted from person to person via bodily fluids because the virus is present in varying concentrations in the blood, semen, vaginal fluid, and breast milk. It can be spread by sexual contact with an infected person, by sharing needles/syringes with someone who is infected, or, less commonly (and rare in countries where blood is screened for HIV antibodies), through transfusions with infected blood.
Environment: HIV does not survive well in the environment outside of the body. Therefore, it is highly unlikely that the disease can be transmitted through contact with the environment, such as public toilet seats.
Kissing: Casual contact through closed-mouth or "social" kissing does not put an individual at risk for HIV. However, there is the potential for blood contact with open-mouth kissing. The risk for acquiring the virus from open-mouth kissing is low, and the Centers for Disease Control and Prevention (CDC) has only investigated one case in which HIV infection may be attributed to blood contact during open-mouth kissing. The CDC recommends that individuals avoid open-mouth kissing with an infected person.
There have been medical reports that found that HIV transmission resulted after a human bite. Severe trauma and extensive tissue tearing were reported in each of these cases. However, biting is not a common way of transmitting the disease.
Saliva, tears, and sweat:
HIV has been found in saliva and tears in very low quantities and concentrations in some AIDS patients. However, a small amount of HIV in body fluid does not necessarily mean that that fluid can transmit the virus. Contact with saliva, tears, or sweat has never been shown to result in transmission of HIV.
According to numerous studies, there is no evidence to suggest that HIV has been transmitted through insects, even in areas that have high numbers of AIDS patients and mosquito populations. HIV can only live for a short time inside an insect and does not reproduce inside insects.
Effectiveness of condoms:
If the condom is used properly during sexual intercourse, an individual can greatly reduce the risk of acquiring or transmitting STDs, including HIV. Several studies show that using condoms correctly and consistently can reduce the breakage rates of latex condoms to less than two percent.
There are many types and brands of condoms, but only latex or polyurethane condoms are highly effective in preventing HIV transmission.
According to the CDC, natural membrane condoms (such as lambskin) have natural pores and can possibly transmit diseases. Therefore, lambskin condoms should not be used to reduce the risk of HIV.
hiv and pregnancy
Babies born to HIV-infected mothers may become infected before or during birth or through breastfeeding. Therefore, the U.S. Centers for Disease Control and Prevention (CDC) recommends that all pregnant women get tested for HIV.
Antiretroviral therapy can significantly reduce the likelihood of an HIV-infected pregnant mother passing the virus to her baby. Patients who were taking antiretroviral medication before becoming pregnant should talk to their healthcare providers to determine the safest and most effective treatment option. In general, efavirenz (Sustiva®), stavudine (Zerit®), hydroxyurea (Droxia® or Hydrea®), and the oral liquid formulation of amprenavir (Agenerase®) should not be taken during pregnancy because they may cause harm to the fetus.
HIV infection rates shortly before or after birth have been shown to drop to as low as one to two percent for babies if their mothers take combination antiretroviral therapy during pregnancy, as well as zidovudine or nevirapine (Viramune®) preventative therapy during labor and after birth.
The baby is more likely to become infected if the vaginal delivery takes a long time because the newborn is exposed to the mother's blood and vaginal secretions. Mothers with high levels of the virus in their blood might reduce their risk if they deliver their baby by cesarean section (surgical delivery of an infant), also called C-section. While a C-section can reduce the risk of transmission during birth, it is not typically necessary in patients who undergo antiretroviral therapy.
HIV-infected mothers should not breastfeed their babies because the virus may be transmitted via the breast milk. Instead, baby formulas should be used.
antiretroviral side effects
Individuals taking antiretroviral drugs often have a difficult time following complicated drug plans. The current recommended treatment requires patients to take several antiretroviral drugs every day from at least two different classes. Also, some of the drugs require not eating before or after taking the pill and may cause side effects such as nausea and vomiting. Other antiretroviral drugs may cause serious medical problems, including changes in body fat distribution, increased lipid (fat) levels in the blood, and changes in glucose metabolism. Changes in glucose metabolism may lead to the onset or worsening of diabetes.
The National Institute of Allergy and Infectious Diseases is among many research organizations that is investigating simpler, less toxic, and more effective drug plans.