What Is the HIV Virus? Human Immunodeficiency Virus

Medically Reviewed on 10/13/2022
What Is the HIV Virus
HIV (human immunodeficiency virus) is a virus that attacks and damages the immune system

HIV (human immunodeficiency virus) damages immune system cells and weakens their ability to defend against diseases and infections. The main cells affected are CD4 cells, a type of white blood cell or T cell.

HIV needs a host cell to replicate its genetic code and create new viral particles. The virus cannot enter a cell unless it has a CD4 receptor. CD4 receptors are located on immune cells, such as helper T cells, which help the immune system combat infections. 

In the absence of antiviral medicine, HIV usually takes over CD4 cells and converts them into damaged cells that cannot attack the infectious agents that attack the body. This can weaken the immune system and make a person more prone to infections and impair the ability to recover from even a minor injury or sickness. 

HIV infection leads to AIDS (acquired immunodeficiency syndrome) over time. AIDS is a fatal disease where the immune system weakens, allowing life-threatening infections and malignancies to spread throughout the body.

What are different types of HIV?

HIV replicates itself indefinitely. Some strains proliferate more quickly and spread more easily from person to person than others. 

Your doctor will be able to treat you more efficiently if they know what strain of HIV you have. HIV strains can be detected by a blood test. The same test can indicate HIV medications that will work for you. There are two types of HIV:

  • HIV-1: First discovered and most common strain globally
  • HIV-2: Less pathogenic and predominantly found in West Africa

HIV-1 and HIV-2 are further classified into subtypes and groups.


  • Group M is the most prevalent and is principally responsible for the global HIV epidemic.
  • Group M subtypes A, B, C, D, F, G, H, J, and K are genetically different. Some of these subtypes unite to generate a hybrid virus called the circulating recombinant form.
  • Because subtype B is the most common HIV-1 subtype in America, Australia, Asia, and Western Europe, the bulk of HIV clinical research is concentrated in these regions.
  • Even though subtype C accounts for roughly half of all HIV patients, little research on this subtype has been done.
  • Outlier or O group and non-M/O or N group are quite rare and only found in a few regions.


Types A and B are typically found in West Africa and are rarely found in Brazil, Europe, the U.S., and India.

Usually, HIV refers to HIV-1. The main difference between HIV-1 and HIV-2 infections is the mechanism of retroviral pathogenesis, which is currently unclear.


What is HIV? See Answer

What are the signs and symptoms of HIV?

When first infected with HIV, there may be no noticeable symptoms. HIV or AIDS develops in stages, with each stage causing different symptoms.

Acute infection or seroconversion

A person can get infected with HIV within 2-6 weeks after being exposed. During this stage, the body attempts to fight the virus, resulting in initial symptoms that are frequently compared to flu symptoms. This stage usually lasts 1-2 weeks before transitioning to a non-symptomatic stage. Symptoms during this stage may include:

Asymptomatic stage

Once the initial symptoms have subsided, the second stage begins, during which the infection takes over the body as the immune system loses the struggle

This is often a lengthy period, perhaps lasting 10 years or more, during which the patient may experience no symptoms at all. Inside the body, however, the virus is steadily eliminating the CD4 T cells, which should typically be between 450 and 1,400 cells/μL.

This is the period during which many infected persons may unknowingly spread the virus to others.


AIDS is the most advanced stage of the illness. The CD4 T cell count falls below 200 cells/μL. During this stage, more serious symptoms may appear:

Consult your doctor right away if you notice any of these symptoms. 

If left untreated, HIV infection progresses and eventually leads to late-stage HIV/AIDS. If an HIV-positive person has a detectable viral load, they can transmit the virus through blood, sperm, vaginal fluid, anal mucus, and breast milk.

How is HIV diagnosed?

In order to diagnose HIV/AIDS, a variety of tests may be ordered:

  • Antibody screening test or immunoassay: Detects the infection within 3-6 months of exposure
  • Antigen test: May test positive as early as 3 weeks after exposure
  • RNA test: A highly expensive test that detects the disease about 10 days following exposure

What are treatment options for HIV?

To reduce HIV levels in the body, effective HIV treatment involves a combination of anti-HIV medications, which should be started immediately. Antiretroviral therapy (ART), highly active antiretroviral therapy (HAART), and antiretrovirals (ARVs) are terms used to describe HIV therapy. These drugs work to stop HIV by inhibiting HIV from reproducing

  • Nucleoside reverse transcriptase inhibitors (NRTIs)
    • Work by inhibiting reverse transcriptase, an enzyme required by the virus to generate new viruses
    • Suppress the emergence of new viruses by inserting themselves into the virus' DNA during replication (a typical HAART program will include two of these drugs)
  • Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
    • Bind to reverse transcriptase and causes the enzyme to stop working
    • May be prescribed as the third medicine in first-line HAART treatment
  • Protease inhibitors (PIs)
    • Inhibit protease, an enzyme required by the virus for reproduction
    • Can be utilized as the third medicine in a first-line HAART treatment program
    • Require the addition of a pharmacokinetic enhancer, which is a medication that increases the effectiveness of PIs against HIV
  • Integrase strand transfer inhibitors (INSTIs) or simply integrase inhibitors
    • Prevent HIV replication (HIV inserts its DNA into the DNA of CD4 cells to replicate)
    • Block the HIV enzyme that aids in the transmission
    • Can be utilized as the third medicine in a first-line HAART treatment program
  • Entry inhibitors or CCR5s (chemokine coreceptor antagonists)
    • Keep the virus out of the cell by inhibiting CCR5, a protein found on the surface of CD4 cells, which prevents the virus from spreading
    • A blood test can tell your doctor if your HIV strand will respond to this class of drugs
  • Fusion inhibitors
    • Prevent HIV from merging with CD4 cell membranes, which prevents the virus from entering the cell
    • Not currently indicated as a first-line treatment and instead as an option for those who have had previous therapy and need to switch regimens

Although there is no cure for HIV, it can be treated with appropriate medicines so that the blood viral load remains low. 

People who undergo ART can enjoy a healthy life without the risk of sexually transmitting the virus to their partners as long as precautions are taken. Pre-and post-exposure prophylaxis medications can effectively prevent HIV transmission to HIV-negative people. 

The most important aspect of managing AIDS is to continue taking your medications and fight off opportunistic infections as soon as they appear.

Medically Reviewed on 10/13/2022
Image Source: iStock image

What Are HIV and AIDS? https://www.hiv.gov/hiv-basics/overview/about-hiv-and-aids/what-are-hiv-and-aids

HIV and AIDS - Basic facts. https://www.unaids.org/en/frequently-asked-questions-about-hiv-and-aids

Human Immunodeficiency Virus (HIV). https://www.immunology.org/public-information/bitesized-immunology/pathogens-and-disease/human-immunodeficiency-virus-hiv

Human Immunodeficiency Virus (HIV). https://www.yalemedicine.org/conditions/human-immunodeficiency-virus-hiv