HIV1

HIV-1, or human immunodeficiency virus type 1, is the predominant variant of the lentivirus family that causes most HIV infections worldwide. It primarily infects CD4+ T cells and other immune cells, leading to progressive immune system damage and, if untreated, Acquired Immunodeficiency Syndrome (AIDS). HIV-1 is an enveloped, single-stranded positive-sense RNA retrovirus in the family Retroviridae. Its genome encodes structural proteins gag, pol and env, and regulatory and accessory proteins such as tat, rev, nef, vif, vpr and vpu. The virus enters cells by binding to the CD4 receptor and a co-receptor (CCR5 or CXCR4) and reverse-transcribes its RNA into DNA, which integrates into the host genome, enabling persistent infection.

Transmission occurs mainly through unprotected sexual contact, contaminated blood, and from mother to child during pregnancy, birth, or breastfeeding. It is not transmitted by casual contact or ordinary environmental exposure.

Clinically, infection proceeds through acute viremia followed by a chronic phase; without treatment, CD4+ T-cell counts decline, increasing the risk of opportunistic infections and cancers, leading to AIDS. Diagnosis uses HIV-1 antibody/antigen tests, nucleic acid tests for RNA or DNA, and p24 antigen tests; fourth-generation assays can detect infection earlier.

Treatment is with combination antiretroviral therapy (ART), typically three or more drugs from at least two drug classes, to suppress viral replication, restore immune function, and reduce HIV-related illness and transmission. ART requires lifelong adherence.

Prevention includes ART for pregnant people living with HIV to prevent vertical transmission, pre-exposure prophylaxis (PrEP) for high-risk individuals, post-exposure prophylaxis (PEP), and safe-sex and harm-reduction strategies.