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HIV / AIDS

AIDS was first reported in the United States in 1981 and has since become a major worldwide epidemic. AIDS is caused by the human immunodeficiency virus, or HIV. By killing or damaging cells of the body's immune system, HIV progressively destroys the body's ability to fight infections and certain cancers. People diagnosed with AIDS may get life-threatening diseases called opportunistic infections. These infections are caused by microbes such as viruses or bacteria that usually do not make healthy people sick.

What are HIV and AIDS?

HIV, or human immunodeficiency virus, is the virus that causes AIDS. HIV attacks the immune system by destroying CD4 positive (CD4+) T cells, a type of white blood cell that is vital to fighting off infection. The destruction of these cells leaves people infected with HIV vulnerable to other infections, diseases and other complications.

AIDS is the final stage of HIV infection. A person infected with HIV is diagnosed with AIDS when he or she has one or more opportunistic infections, such as pneumonia or tuberculosis, and has a dangerously low number of CD4+ T cells (less than 200 cells per cubic millimeter of blood).

How HIV Causes AIDS

HIV destroys CD4 positive (CD4+) T cells, which are white blood cells crucial to maintaining the function of the human immune system. As HIV attacks these cells, the person infected with the virus is less equipped to fight off infection and disease, ultimately resulting in the development of AIDS.

Most people who are infected with HIV can carry the virus for years before developing any serious symptoms. But over time, HIV levels increase in the blood while the number of CD4+ T cells decline. Antiretroviral medicines can help reduce the amount of virus in the body, preserve CD4+ T cells and dramatically slow the destruction of the immune system.

People who are not infected with HIV and generally are in good health have roughly 800 to 1,200 CD4+ T cells per cubic millimeter (mm3) of blood. Some people who have been diagnosed with AIDS have fewer than 50 CD4+ T cells in their entire body.

HIV infected Cells

Normal T-cells

 

 

 

 

T Cells

HIV-infected T-cells

 

 

 

HIV Transmission

Quick Facts About HIV Transmission

Risk Factors

HIV is found in the blood, semen, or vaginal fluid of someone who is infected with the virus. You may be at increased risk of becoming infected with HIV if you:

Symptoms of HIV / AIDs

Early Symptoms

In the first stages of HIV infection, most people will have very few, if any, symptoms. Within a month or two after infection, they may experience a flu-like illness, including:

These symptoms usually disappear within a week to a month and are often mistaken for another viral infection, such as flu. However, during this period people are highly infectious because HIV is present in large quantities in genital fluids and blood. Some people infected with HIV may have more severe symptoms at first or symptoms that last a long time, while others may have no symptoms for 12 years or more.

Later Symptoms

During the late stages of HIV infection, the virus severely weakens the immune system, and people infected with the virus may have the following symptoms:

Each of these symptoms can be related to other illnesses. The only way to find out if you are infected with HIV is to get tested.

Testing and Diagnosis of HIV

Routine HIV Testing

Of the estimated 1.1 million Americans currently living with HIV, 21 percent do not know they are infected. People who have been infected recently with HIV often have few to no symptoms yet are extremely infectious and may unknowingly transmit the virus to others.

Therefore, the Centers for Disease Control and Prevention (CDC) recommends HIV testing for adults, adolescents, and pregnant women during routine medical care. Regular HIV screenings allow healthcare providers to identify people who are not aware that they are infected with HIV, so that they can be counseled on the need to avoid high-risk behaviors, instructed on safe-sex practices, and given information about starting antiretroviral therapy. HIV testing can also be performed anonymously if a person is concerned about confidentiality.

Types of HIV Tests

Healthcare providers can test a sample of blood to see if it contains human antibodies (disease-fighting proteins) specific to HIV. The two key types of HIV antibody tests are the enzyme-linked immunosorbent assay (ELISA) and the Western blot.

However, these antibody tests may not detect HIV antibodies in someone who has been recently infected with HIV (within 1 to 3 months of infection). In these situations, healthcare providers can test the blood for the presence of HIV genetic material. This test is extremely critical for identifying recently infected people who are at risk for unknowingly infecting others with HIV.

HIV Testing in Infants

CDC recommends that all pregnant women get tested for HIV before and/or during delivery. Knowing the HIV status of the mother allows physicians to prevent mother-to-child HIV transmission by providing antiretroviral treatment to both mothers infected with HIV and their newborn infants. However, it is difficult to determine if a baby born to a mother infected with HIV is actually infected because babies carry their mothers’ HIV antibodies for several months. Today, healthcare providers can conduct an HIV test for infants between ages 3 months and 15 months. Researchers are now evaluating several blood tests to determine which ones are suitable for testing babies younger than 3 months.

Treatment of HIV/AIDS

In the early 1980s when the HIV/AIDS epidemic began, people with AIDS were not likely to live longer than a few years.

Today, there are 31 antiretroviral drugs (ARVs) approved by the Food and Drug Administration to treat HIV infection. These treatments do not cure people of HIV or AIDS. Rather, they suppress the virus, even to undetectable levels, but they do not completely eliminate HIV from the body. By suppressing the amount of virus in the body, people infected with HIV can now lead longer and healthier lives. However, they can still transmit the virus and must continuously take antiretroviral drugs in order to maintain their health quality.

Classes of HIV/AIDS Antiretroviral Drugs

The antiretroviral medications used to treat HIV/AIDS currently are organized into five major drug classes.

Reverse Transcriptase (RT) Inhibitors interfere with the critical step during the HIV life cycle known as reverse transcription. During this step, the HIV enzyme RT converts HIV RNA to HIV DNA. There are two main types of RT inhibitors.

  1. Nucleoside/nucleotide RT inhibitors are faulty DNA building blocks. When these faulty pieces are incorporated into the HIV DNA (during the process when HIV RNA is converted to HIV DNA), the DNA chain cannot be completed, thereby blocking HIV from replicating in a cell.
  2. Non-nucleoside RT inhibitors bind to RT, interfering with its ability to convert the HIV RNA into HIV DNA.

Protease Inhibitors interfere with the protease enzyme that HIV uses to produce infectious viral particles.

Fusion/Entry Inhibitors interfere with the virus' ability to fuse with the cellular membrane, thereby blocking entry into the host cell.

Integrase Inhibitors block integrase, the enzyme HIV uses to integrate genetic material of the virus into its target host cell.

Multidrug Combination Products combine drugs from more than one class into a single product. To combat virus strains from becoming resistant to specific antiretroviral drugs, healthcare providers recommend that people infected with HIV take a combination of antiretroviral drugs known as highly active antiretroviral therapy (HAART). The HAART strategy combines drugs from at least two different antiretroviral drug classes.

In Development

Another HIV/AIDS drug class known as maturation inhibitors is still in development. If successful, they could potentially prevent HIV from properly assembling and maturing. For example, these treatments could block HIV from forming a protective outer coat or from emerging from human cells.

Medication Adherence and Drug Resistance

People infected with HIV who take antiretroviral treatments sometimes find it difficult to adhere to their drug regimens. This can be caused by the complexity of having to take several drugs each day or the unpleasant side effects that may result from some medicines, such as nausea and vomiting. However, when patients fail to take their medicines, HIV has an opportunity to create more variations of itself, including strains that are resistant to antiretroviral drugs. Therefore, it is important for people to continue taking their medicines as prescribed by their healthcare providers.

Complications of Medications and Side Effects

Antiretroviral drugs can, in rare cases, cause serious medical complications, including metabolic changes such as abnormal fat distribution, abnormal lipid and glucose metabolism, and bone loss. Monitoring for these complications and side effects is the responsibility of patients and their healthcare providers.

Prevention of HIV/AIDS

Consistent use of male latex condoms can help protect against HIV infection. Credit: NIAID

Currently, there is no vaccine to prevent HIV infection nor is there a cure for HIV/AIDS. To reduce your risk of becoming infected with HIV or transmitting the virus to others:

Antiretroviral Therapy to Reduce the Transmission of HIV

The advent of antiretroviral therapy (ART) in the early 1980s and highly active antiretroviral therapy (HAART) regimens have dramatically reduced the morbidity and mortality associated with HIV infection through sustained reduction in HIV viral replication. This sustained suppression of viral load has led researchers to consider ARVs as a prevention tool; ARVs would lower the viral load and, thus, the infectiousness of an HIV-infected person to an uninfected partner. This research is particularly relevant for prevention among serodiscordant couples, many of whom will continue to be sexually active despite their differing infection status.

Additionally, researchers are considering the possibility that antiretroviral drugs might be used by uninfected, at-risk persons before exposure to HIV and that these drugs might be able to block or prevent infection from occurring. This potential strategy, called Pre-Exposure Prophylaxis (PrEP), does not require participation of a sexual partner (as does condom use), could be highly complementary to other prevention strategies, and empowers women who wish to protect themselves from HIV.


Last updated April 4, 2013


Reference: National Institute of Allergy and Infectious Diseases