What is the difference between HIV and AIDS?

HIV (Human Immunodeficiency Virus) is the virus that causes the infection. AIDS (Acquired Immunodeficiency Syndrome) is the most advanced stage of HIV infection. A person is diagnosed with AIDS when their immune system is severely damaged, typically indicated by a CD4+ T-cell count below 200 cells/mm³ or the presence of specific opportunistic infections and cancers. Not everyone with HIV has AIDS, especially with effective treatment, but everyone with AIDS has HIV.

How is HIV transmitted from one person to another?

HIV is primarily transmitted through specific bodily fluids: blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, and breast milk. The most common routes are unprotected sexual contact (vaginal, anal, oral), sharing contaminated needles or syringes (e.g., for drug injection), and from an infected mother to her child during pregnancy, childbirth, or breastfeeding. It is not transmitted through casual contact like hugging, kissing, sharing food, or mosquito bites.

Currently, there is no widely available cure for HIV. However, highly effective antiretroviral therapy (ART) can suppress the virus to undetectable levels, allowing people with HIV to live long, healthy lives and preventing transmission. While a few cases of 'functional cure' have been reported in specific research settings (e.g., bone marrow transplant patients), these are not scalable or safe for the general population. Research for a cure continues actively.

What are opportunistic infections in the context of AIDS?

Opportunistic infections are illnesses caused by pathogens (bacteria, viruses, fungi, parasites) that typically do not cause disease in people with healthy immune systems. However, in individuals with AIDS, whose immune systems are severely weakened by HIV, these pathogens seize the 'opportunity' to cause severe and life-threatening infections. Examples include *Pneumocystis jirovecii* pneumonia, Kaposi's sarcoma, and cryptococcal meningitis.

What is the role of CD4+ T-cells in HIV infection?

CD4+ T-cells, also known as T-helper cells, are critical components of the immune system. They act as 'generals' or 'coordinators,' signaling to other immune cells (like B-cells and cytotoxic T-cells) to initiate and regulate immune responses against pathogens. HIV specifically targets and destroys these CD4+ T-cells. As their numbers decline, the entire immune system becomes compromised, leading to immunodeficiency and the development of AIDS.

How does antiretroviral therapy (ART) work?

ART is a combination of drugs that target different stages of the HIV life cycle. For instance, reverse transcriptase inhibitors block the conversion of viral RNA into DNA, protease inhibitors prevent the assembly of new viral particles, and integrase inhibitors stop the viral DNA from integrating into the host genome. By attacking the virus at multiple points, ART effectively suppresses viral replication, reduces the viral load, and allows the immune system to recover, preventing progression to AIDS.

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Version 1Updated 22 Mar 2026

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Acquired Immunodeficiency Syndrome (AIDS) is a chronic, potentially life-threatening condition caused by the Human Immunodeficiency Virus (HIV). HIV is a retrovirus that primarily targets and destroys CD4+ T-lymphocytes, which are crucial components of the human immune system. The progressive depletion of these helper T-cells leads to a severe compromise of the body's immune defenses, rendering th…

Quick Summary

AIDS, or Acquired Immunodeficiency Syndrome, is the advanced stage of infection caused by the Human Immunodeficiency Virus (HIV). HIV is a retrovirus that primarily attacks and destroys CD4+ T-lymphocytes, which are crucial cells of the immune system.

The virus uses an enzyme called reverse transcriptase to convert its RNA genome into DNA, which then integrates into the host cell's DNA. This leads to a progressive decline in CD4+ T-cell count, severely weakening the body's ability to fight off infections.

Transmission occurs mainly through unprotected sexual contact, sharing contaminated needles, and from mother to child. Symptoms can range from flu-like illness in the acute phase to a long asymptomatic period, eventually leading to opportunistic infections and certain cancers when the immune system is severely compromised (AIDS stage).

While there is no cure, antiretroviral therapy (ART) effectively manages HIV, suppresses viral load, and prevents progression to AIDS, allowing individuals to live healthy lives. Prevention focuses on safe practices and medication like PrEP and PEP.

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Key Concepts

HIV Life Cycle: Reverse Transcription

After HIV enters a host cell, its single-stranded RNA genome needs to be converted into DNA to integrate into…

Role of CD4+ T-cells in Immunodeficiency

CD4+ T-cells are central orchestrators of the adaptive immune response. They recognize antigens presented by…

Antiretroviral Therapy (ART) Drug Classes

ART is not a single drug but a combination of drugs from different classes, each designed to interfere with a…

Causative Agent: — HIV (Human Immunodeficiency Virus), a retrovirus.

Genetic Material: — Two identical single-stranded RNA molecules.

Key Enzymes: — Reverse transcriptase, Integrase, Protease.

Target Cells: — CD4+ T-lymphocytes (Helper T-cells).

Mechanism: — HIV RNA

xrightarrow{\text{Reverse Transcriptase}}

Viral DNA

xrightarrow{\text{Integrase}}

Host DNA (Provirus)

ightarrow

Viral replication

ightarrow

CD4+ T-cell destruction.

AIDS Diagnosis: — CD4+ T-cell count <

200,\text{cells/mm}^3

or presence of AIDS-defining opportunistic infections/cancers.

Transmission: — Unprotected sexual contact, contaminated needles, mother-to-child (pregnancy, birth, breastfeeding).

NO Transmission: — Casual contact, insect bites, sharing food.

Diagnosis: — ELISA (screening), Western Blot/NAT (confirmatory).

Treatment: — ART (Antiretroviral Therapy) - combination of drugs targeting different viral life cycle stages (e.g., NRTIs, NNRTIs, PIs, INSTIs). Not a cure, but suppresses viral load.

To remember the key enzymes of HIV and their functions, think of R.I.P. HIV:

R — Reverse Transcriptase: Converts RNA to DNA.

I — Integrase: Integrates viral DNA into host DNA.

P — Protease: Processes viral proteins for assembly.

This mnemonic helps recall the three critical viral enzymes that are also targets for antiretroviral drugs.

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