Describe and discuss transmission, pathogenesis, clinical manifestations, treatment and prevention of HIV/AIDS.

Human immunodeficiency virus (HIV) is a retrovirus that causes acquired immunodeficiency syndrome (AIDS). HIV/AIDS is one of the most catastrophic pandemics in human history and continues to be a major health challenge worldwide. Understanding how HIV is transmitted, its pathogenesis, clinical manifestations, treatment and prevention are essential for managing this infection.

Transmission of HIV occurs through contact with body fluids such as blood, semen or vaginal secretions—through sexual intercourse, mother-to-child transmission during pregnancy or childbirth, sharing contaminated needles or syringes used for injecting drugs and from organ transplants from an infected donor. The risk of infection among adults increases when there is unprotected anal sex between men or when multiple partners are involved in any type of sexual activity.

Following transmission via direct contact with infected body fluids such as blood or semen, the virus replicates within host cells by entering them via receptor-mediated endocytosis after binding to CD4 co-receptor molecules on the cell surface. This initiates an immune response that results in production of antibodies against viral proteins which can then be detected using assays like ELISA (enzyme-linked immunosorbent assay). Once inside the cell, viral RNA replicates into double stranded DNA using reverse transcriptase enzyme which integrates into the host genome resulting in long term persistence even if the virus levels are low in peripheral circulation. This process leads to progressive destruction of CD4 T cells leading to demise of adaptive immunity and development of AIDS defined by CDC criteria based on number of remaining T helper lymphocytes (<200 cells/mm3) causing individuals to succumb to infections caused due diseases like cryptococcal meningitis or toxoplasmosis gondii encephalitis etc., resulting in death unless aggressive drug therapy is initiated early upon diagnosis.

The clinical manifestations associated with HIV/AIDS include symptoms related to various opportunistic infections along with systemic symptoms like fatigue , weight loss , fever , night sweats etc . Various fungal , protozoal & bacterial organisms including Pneumocystis jirovecii pneumonia(PCP), Mycobacterium Avium complex(MAC), Candidiasis , Cryptococcal Meningitis along with Kaposi Sarcoma may develop during advanced stages leading to further decline in health status . The World Health Organization recommends initiating antiretroviral therapy once CD4 counts drops below 500cells/mm3 for HIV positive individuals without any opportunistic complications . Antiretroviral drugs help suppress replication & reduce vial load eventually improving patient’s overall well being provided they adhere strictly & continously take medications as prescribed by physicians . Standard ART regimen includes two nucleoside reverse transcriptase inhibitors combined with either a nonnucleoside reverse transcriptase inhibitor (NNRTI) or protease inhibitor (PI).