Give an elaborate account on AIDS.

I. Etiology and Pathogenesis of HIV/AIDS

HIV, a retrovirus belonging to the lentivirus subfamily, exists in two primary types: HIV-1 and HIV-2. HIV-1 is responsible for the vast majority of infections globally. The virus primarily infects CD4+ T helper cells, macrophages, and dendritic cells. The pathogenesis of HIV infection can be divided into three stages:

• Acute Infection: Occurs within 2-4 weeks of infection, characterized by flu-like symptoms. High viral load and a rapid decline in CD4+ T cell count.
• Clinical Latency: A period of clinical quiescence where the virus continues to replicate at low levels. CD4+ T cell count gradually declines over years.
• AIDS: Defined by a CD4+ T cell count below 200 cells/µL or the presence of opportunistic infections or cancers.

HIV replicates through a complex process involving reverse transcription, integration into the host cell genome, and viral assembly. This process leads to the destruction of CD4+ T cells, compromising the immune system.

II. Clinical Manifestations of AIDS

The clinical presentation of AIDS is diverse, ranging from asymptomatic infection to severe opportunistic infections. Common symptoms include:

• Early Symptoms: Fever, fatigue, rash, swollen lymph nodes.
• Opportunistic Infections: Pneumocystis pneumonia (PCP), candidiasis, tuberculosis (TB), cytomegalovirus (CMV) infection, toxoplasmosis.
• Cancers: Kaposi's sarcoma, non-Hodgkin's lymphoma, cervical cancer.
• Neurological Complications: HIV-associated neurocognitive disorder (HAND), peripheral neuropathy.

The specific opportunistic infections and cancers that develop depend on the individual’s immune status and geographic location.

III. Diagnosis of HIV/AIDS

Diagnosis of HIV infection involves a combination of antibody and antigen tests:

• Antibody Tests: Detect antibodies produced by the body in response to HIV. These tests may not be positive immediately after infection (window period).
• Antigen/Antibody Combination Tests: Detect both HIV antibodies and HIV p24 antigen, reducing the window period.
• Viral Load Tests: Measure the amount of HIV RNA in the blood. Used to monitor disease progression and response to treatment.
• CD4+ T Cell Count: Measures the number of CD4+ T cells in the blood. Used to assess immune function and guide treatment decisions.

IV. Prevention of HIV/AIDS

Prevention strategies are crucial in controlling the HIV/AIDS epidemic:

• Safe Sex Practices: Consistent and correct use of condoms.
• Pre-Exposure Prophylaxis (PrEP): Daily oral medication for HIV-negative individuals at high risk of infection.
• Post-Exposure Prophylaxis (PEP): Emergency medication taken within 72 hours of potential exposure to HIV.
• Needle Exchange Programs: Reduce the risk of HIV transmission among intravenous drug users.
• Mother-to-Child Transmission (MTCT) Prevention: ART for pregnant women with HIV, elective cesarean section, and infant prophylaxis.
• Blood Safety: Screening of blood products for HIV.

V. Treatment of HIV/AIDS

Antiretroviral therapy (ART) is the mainstay of HIV treatment. ART involves a combination of drugs that suppress viral replication, allowing the immune system to recover. Common ART drug classes include:

• Nucleoside/Nucleotide Reverse Transcriptase Inhibitors (NRTIs)
• Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
• Protease Inhibitors (PIs)
• Integrase Strand Transfer Inhibitors (INSTIs)
• Entry Inhibitors

Early initiation of ART is recommended for all HIV-positive individuals, regardless of CD4+ T cell count. Undetectable = Untransmittable (U=U) – individuals on effective ART with an undetectable viral load cannot sexually transmit HIV.

VI. Global Impact and Current Scenario

According to UNAIDS data (2022), 39.0 million people were living with HIV globally in 2022. Sub-Saharan Africa remains the most affected region, accounting for over half of all new HIV infections. Significant progress has been made in reducing new infections and AIDS-related deaths, but challenges remain, including stigma, discrimination, and access to treatment. The COVID-19 pandemic disrupted HIV prevention and treatment services, leading to setbacks in the global response.