A retrovirus that targets CD4+ T lymphocytes and other immune cells, progressively impairing the immune system and leading to acquired immunodeficiency syndrome (AIDS).
Explanation
Human immunodeficiency virus is a member of the Lentivirus group of retroviruses. It has a single‑stranded RNA genome and depends on the enzyme reverse transcriptase to synthesize DNA from its RNA template. This DNA integrates into the genome of infected cells, establishing a persistent infection. HIV primarily infects CD4+ T helper lymphocytes, macrophages and dendritic cells. Over time it depletes CD4+ T cells, undermining cell‑mediated and humoral immune responses and leaving individuals vulnerable to opportunistic pathogens and certain cancers. Two types infect humans: HIV‑1 and HIV‑2. HIV‑1 is responsible for the global pandemic; HIV‑2 is largely restricted to West Africa and usually progresses more slowly. Researchers believe HIV crossed into humans from non‑human primates in the early twentieth century and was recognized in the early 1980s as the cause of AIDS. Laboratory diagnosis involves detecting antibodies, viral proteins such as p24 or viral RNA. Without treatment the infection passes through an acute phase with high viral load, a clinical latency phase lasting years, and eventually progression to AIDS. Combination antiretroviral therapy suppresses viral replication by targeting multiple stages of the viral life cycle including reverse transcription, integration and proteolytic processing. Because the virus mutates rapidly, effective control requires multiple agents to limit drug resistance. Long‑term adherence is necessary to maintain viral suppression and prevent immune decline. There is currently no vaccine or cure, although research is ongoing into vaccine candidates, broadly neutralizing antibodies and strategies aiming for functional cure.
Transmission and Management
HIV is transmitted when body fluids containing the virus come into contact with mucosal surfaces or bloodstream. Common transmission routes include unprotected sexual intercourse, sharing contaminated needles or syringes, transfusion of unscreened blood products, and vertical transmission from mother to child during pregnancy, childbirth or breastfeeding. In parts of sub‑Saharan Africa heterosexual transmission is the primary driver of the epidemic, whereas in many industrialized countries infections are more common among men who have sex with men or people who inject drugs. Preventive measures include consistent condom use, safe blood screening, sterile injection equipment, and pre‑exposure or post‑exposure prophylaxis for people at increased risk. Antiretroviral therapy during pregnancy and avoidance of breastfeeding where safe alternatives exist have reduced mother‑to‑child transmission to very low levels. Opportunistic infections such as Pneumocystis pneumonia, tuberculosis and candidiasis often signal progression to AIDS. Prophylactic medications and timely treatment of these conditions can prolong survival. Public health responses combine education, access to testing, treatment and harm‑reduction services to lower transmission rates. HIV remains a major global health issue. Early diagnosis and lifelong access to effective antiretroviral therapy allow many infected individuals to maintain near normal life expectancy and reduce the risk of transmission. Continued research, prevention efforts and equitable access to treatment are essential to control the pandemic. Related Terms: AIDS, Retrovirus, Antiretroviral therapy, CD4+ T cell, Viral load