[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Other RNA viruses](https://durgical.com/en/microbiology/groups/other-rna-viruses/) › Human immunodeficiency virus [Microbiology](https://durgical.com/en/microbiology/) · [Other RNA viruses](https://durgical.com/en/microbiology/groups/other-rna-viruses/) # Human immunodeficiency virus - Virus - Enveloped - Exam priority: high A virus that slowly destroys the body's defences (CD4 cells). Untreated it leads to AIDS; with antiretrovirals people live long lives. Updated 2026-11-01 Also called: HIV, HIV-1, HIV-2 ## Key points - Retrovirus (Lentivirus) with two copies of positive-sense RNA and reverse transcriptase - gp120 binds CD4 and CCR5 or CXCR4; gp41 mediates fusion - Fourth-generation tests detect antibodies and p24 antigen - CD4 below 200 cells/µL defines advanced disease - Tuberculosis is the leading cause of death in people with HIV - Undetectable = untransmittable ## At a glance **Shape** Spherical, with a cone-shaped capsid **Genome** Single-stranded, positive-sense RNA, diploid (two copies) **Envelope** Enveloped **Family** Retroviridae, genus Lentivirus **Size** About 80 to 120 nm ## Morphology - Envelope with gp120 (binds CD4) and gp41 (fusion) - Cone-shaped p24 capsid holding two RNA copies, reverse transcriptase, integrase and protease - HIV-1 dominates worldwide; HIV-2, less virulent, is concentrated in West Africa ## Transmission - Condomless sex (anal or vaginal) - Blood: shared needles, unscreened transfusions, sharps injuries - Mother to child in pregnancy, delivery or breastfeeding - Not spread by kissing, hugging, food or everyday objects **Reservoir:** Humans; it arose from non-human primates in Africa ### Isolation precautions What the care team adds to standard precautions. - Standard ## Life cycle - Binding: gp120 attaches to CD4 and a co-receptor (CCR5 or CXCR4) - Fusion: gp41 fuses the envelope with the membrane and the capsid enters - Reverse transcription: reverse transcriptase copies RNA into double-stranded DNA - Integration: integrase inserts the viral DNA (provirus) into the cell genome - Replication: the cell transcribes the provirus and makes viral RNA and proteins - Assembly and budding: new particles leave through the cell membrane - Maturation: protease cuts the polyproteins and the virion becomes infectious ## Virulence factors - Progressive loss of CD4 T cells and of cell-mediated immunity - Error-prone reverse transcriptase: high variability and drug resistance - The provirus integrated in latent cells forms a reservoir that blocks cure - Chronic immune activation and damage to the gut mucosa ## Diseases it causes - HIV infection: acute, chronic asymptomatic and AIDS (advanced disease) [HIV infection and AIDS →](https://durgical.com/en/conditions/hiv-infection-and-aids/) - Tuberculosis, the leading opportunistic infection and cause of death in people with HIV [Tuberculosis →](https://durgical.com/en/conditions/tuberculosis/) - Other opportunistic diseases: Pneumocystis pneumonia, cryptococcal meningitis, cerebral toxoplasmosis, Kaposi sarcoma and lymphomas ## Clinical picture - Acute infection: mononucleosis-like illness with fever, sore throat, rash and lymph nodes, or no symptoms - Chronic asymptomatic phase for years with a gradual fall in CD4 - Advanced disease: CD4 below 200 cells/µL or a WHO stage 3 or 4 event - AIDS: opportunistic infections, tuberculosis, defining cancers, wasting ## Diagnosis - Rapid tests or a fourth-generation immunoassay (antibodies plus p24 antigen) - Confirmation with a testing algorithm before treatment starts - Viral load (RNA) for follow-up and CD4 count for staging - Under 18 months, virological testing (PCR), because maternal antibodies interfere - Window period: repeat the test after a recent exposure ## Treatment Combination antiretroviral therapy, started as soon as possible after diagnosis. The classes are: nucleoside/nucleotide reverse transcriptase inhibitors (tenofovir, lamivudine), non-nucleoside inhibitors (efavirenz), integrase inhibitors (dolutegravir), protease inhibitors (darunavir), entry or fusion inhibitors and capsid inhibitors. Resistance emerges when adherence fails; with an undetectable viral load there is no sexual transmission (undetectable = untransmittable). Drug class only; doses and regimens are set by the clinician from the current guideline. In Pharmacology: - [Tenofovir disoproxil](https://durgical.com/en/pharmacology/tenofovir-disoproxil/) - [Lamivudine](https://durgical.com/en/pharmacology/lamivudine/) - [Dolutegravir](https://durgical.com/en/pharmacology/dolutegravir/) - [Efavirenz](https://durgical.com/en/pharmacology/efavirenz/) - [Darunavir](https://durgical.com/en/pharmacology/darunavir/) ## Prevention - Condoms and regular testing for HIV and STIs - Pre-exposure prophylaxis (PrEP) with antiretrovirals for people at risk - Post-exposure prophylaxis (PEP), started as soon as possible after a risky exposure - Prevention of mother-to-child transmission with ART in pregnancy - Sterile equipment and harm-reduction programmes ## In Colombia HIV infection is a mandatory notifiable event in SIVIGILA. Colombia has a concentrated epidemic among men who have sex with men, trans women and people who inject drugs; the care pathway includes antenatal screening, free ART in the health system and access to PrEP and PEP. ## Memory aid HIV "moves in": it knocks (binding), steps inside (fusion), writes itself backwards (reverse transcription), unpacks into the cell's files (integration) and sends out copies that mature on the way out. ## Test yourself Think of the answer, then tap the question to see it. ## Which co-receptors does HIV use besides CD4? CCR5 (macrophage-tropic strains, typical early on) and CXCR4 (T-cell-tropic strains, later). ## What does a fourth-generation HIV test detect? HIV antibodies and p24 antigen, which shortens the window period. ## Which step of the life cycle does dolutegravir block? Integration of viral DNA into the cell genome (integrase inhibitor). ## Why is a six-month-old born to a mother with HIV tested by PCR, not antibodies? Maternal antibodies cross the placenta and can persist up to 18 months. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/human-immunodeficiency-virus/) ## Related - [Human T-lymphotropic virus type 1](https://durgical.com/en/microbiology/human-t-lymphotropic-virus-type-1/) - [Hepatitis C virus](https://durgical.com/en/microbiology/hepatitis-c-virus/) ## Related conditions - [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/) - [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/) ## What the colours mean **Gram-positive** Thick peptidoglycan wall: stains purple. **Gram-negative** Thin wall with an outer membrane: stains pink. **Acid-fast** Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain. [← Back to the group: Other RNA viruses](https://durgical.com/en/microbiology/groups/other-rna-viruses/) Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [HIV and AIDS](https://www.who.int/news-room/fact-sheets/detail/hiv-aids) (World Health Organization (WHO), 2025); [About HIV](https://www.cdc.gov/hiv/about/index.html) (CDC, 2025); [Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions](https://www.cdc.gov/infection-control/hcp/isolation-precautions/appendix-a-type-duration.html) (CDC, 2024). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/microbiology/human-immunodeficiency-virus/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/human-immunodeficiency-virus/