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 can be HIV-positive for many years without developing AIDS. AIDS is diagnosed when the immune system is severely damaged, typically indicated by a very low CD4+ T-cell count (below 200 cells/mm³) or the presence of one or more opportunistic infections or AIDS-defining cancers.

How is HIV transmitted?

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, or oral), sharing contaminated needles or syringes (e.g., for drug injection), and from an HIV-positive mother to her child during pregnancy, childbirth, or breastfeeding. It is NOT transmitted through casual contact, air, water, or insect bites.

What are the common symptoms of HIV infection?

Initial (acute) symptoms, if present, often resemble the flu and may include fever, fatigue, swollen lymph nodes, sore throat, and rash. These usually appear 2-4 weeks after infection and resolve within a few weeks. After this, many people remain asymptomatic for years during the chronic phase. As the immune system weakens, symptoms may include persistent swollen lymph nodes, weight loss, fever, night sweats, fatigue, and recurrent infections. AIDS is characterized by severe opportunistic infections and certain cancers.

How is HIV diagnosed?

HIV is diagnosed through blood or saliva tests that detect antibodies to the virus, antigens (viral proteins), or the virus's genetic material (RNA). Common tests include ELISA (Enzyme-Linked Immunosorbent Assay) for initial screening, followed by confirmatory tests like Western Blot or rapid diagnostic tests. Nucleic Acid Tests (NATs) can detect the virus directly and are used for early detection or to confirm diagnosis. Regular testing is recommended for individuals at risk.

Is there a cure for HIV/AIDS?

Currently, there is no widely available cure for HIV/AIDS. However, significant advancements in medicine have led to highly effective treatments called Antiretroviral Therapy (ART). ART involves taking a combination of drugs daily that suppress the virus, allowing people with HIV to live long, healthy lives, and preventing the progression to AIDS. ART also significantly reduces the risk of transmitting HIV to others, making the virus 'undetectable' and therefore 'untransmittable' (U=U).

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

CD4+ T-cells are crucial white blood cells that play a central role in the immune system, acting as 'helper' cells to coordinate immune responses against pathogens. HIV specifically targets and infects these cells because they express the CD4 receptor, which the virus uses to gain entry. As HIV replicates, it destroys these CD4+ T-cells, progressively weakening the immune system. The decline in CD4+ T-cell count is a key indicator of HIV disease progression and the onset of AIDS.

HIV and AIDS

Biology

NEET UG

Version 1Updated 22 Mar 2026

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Human Immunodeficiency Virus (HIV) is a lentivirus, a subgroup of retroviruses, that causes acquired immunodeficiency syndrome (AIDS). HIV primarily targets and destroys CD4+ T-lymphocytes, which are crucial components of the human immune system. This progressive destruction leads to a severe compromise of the body's ability to fight off infections and certain cancers, eventually culminating in AI…

Quick Summary

HIV (Human Immunodeficiency Virus) is a retrovirus that attacks the immune system, specifically targeting CD4+ T-lymphocytes. This progressive destruction of immune cells leads to Acquired Immunodeficiency Syndrome (AIDS), the final stage of HIV infection, characterized by severe immunodeficiency and susceptibility to opportunistic infections and certain cancers.

HIV is transmitted through specific bodily fluids, primarily via unprotected sexual contact, sharing contaminated needles, or from mother to child. It is not spread through casual contact. The virus uses an enzyme called reverse transcriptase to convert its RNA genome into DNA, which then integrates into the host cell's genome.

Diagnosis involves antibody/antigen tests (like ELISA) and confirmatory tests (like Western Blot or PCR). While there is no cure, Antiretroviral Therapy (ART) effectively manages the infection, suppresses viral load, improves immune function, and prevents progression to AIDS, allowing individuals to live healthy lives and significantly reducing transmission risk.

Prevention strategies include safe sex practices, sterile needle use, and pre-exposure prophylaxis (PrEP).

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Key Concepts

HIV Viral Structure and Genetic Material

HIV is an enveloped virus, meaning it has an outer lipid bilayer derived from the host cell membrane, studded…

Role of Reverse Transcriptase in HIV Replication

Reverse transcriptase is the defining enzyme of retroviruses. After HIV enters a host CD4+ T-cell, its RNA…

Progression from HIV Infection to AIDS

The transition from HIV infection to AIDS is a gradual process driven by the continuous destruction of CD4+…

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

Genetic Material: — Two identical ssRNA strands.

Key Enzymes: — Reverse transcriptase (RNA

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DNA), Integrase (viral DNA into host DNA), Protease (cleaves viral polyproteins).

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

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

NOT Transmitted By: — Casual contact, air, water, insect bites.

AIDS Definition: — CD4+ T-cell count < 200 cells/mm³ or presence of opportunistic infections.

Diagnosis: — ELISA (screening), Western Blot/PCR (confirmation).

Treatment: — ART (Antiretroviral Therapy) - suppresses viral replication, restores immune function, not a cure.

HIV Invades Very Active Immune Defense Systems

HIV: Human Immunodeficiency Virus (the virus)

Invades: Integrase (enzyme that integrates viral DNA)

Very: Viral RNA (genetic material)

Active: AIDS (the disease stage)

Immune: Immunodeficiency (result of infection)

Defense: Decreased CD4+ T-cells (primary target)

Systems: Sex, Sharing needles, Secretions (transmission routes)