Unit
- HIV definition: Human Immunodeficiency Virus attacks the immune system's CD4 cells, progressively weakening the body's ability to fight infections. Without treatment, HIV can lead to Acquired Immunodeficiency Syndrome (AIDS), the most advanced stage of infection.
- AIDS definition: AIDS is diagnosed when CD4 count falls below 200 cells per cubic millimeter or when specific opportunistic infections occur. It represents the final stage of HIV infection if untreated.
- Virus structure: HIV is a retrovirus with RNA genome that integrates into host DNA using reverse transcriptase. This makes it difficult to eradicate and requires lifelong antiretroviral therapy.
- Transmission routes: HIV spreads through blood, semen, vaginal fluids, rectal fluids, and breast milk. Common modes include unprotected sexual contact, sharing needles, from mother to child during pregnancy or breastfeeding, and occupational exposure.
- Window period: After exposure, there is a window period of 2-6 weeks before most tests can detect the virus. During this time, an infected person may transmit HIV but test negative.
- Acute infection: Many people experience flu-like symptoms within 2-4 weeks after infection, known as acute retroviral syndrome. This phase is associated with high viral load and increased transmissibility.
- Chronic infection: Without treatment, HIV progresses to a chronic phase that can last years with few symptoms. The virus continues to replicate and damage the immune system silently.
- Treatment importance: Antiretroviral therapy (ART) suppresses viral replication, allows immune recovery, and prevents progression to AIDS. Adherent individuals can achieve undetectable viral load, meaning no risk of sexual transmission.
- Global burden: According to WHO, approximately 38 million people live with HIV worldwide, with Sub-Saharan Africa accounting for the majority. New infections continue to occur, particularly among key populations.
- Prevention methods: Multiple evidence based prevention strategies include consistent condom use, pre-exposure prophylaxis PrEP, post-exposure prophylaxis PEP, harm reduction services for people who inject drugs, and voluntary medical male circumcision. Combining these approaches provides the most effective protection against HIV acquisition.
- PrEP: Pre exposure prophylaxis involves daily antiretroviral medication taken by HIV negative individuals to prevent infection. When taken consistently, PrEP reduces sexual transmission risk by about 99 percent and is highly effective for people who inject drugs. Routine medical monitoring is required for PrEP users.
- U equals U: Undetectable equals Untransmittable means that people living with HIV who maintain an undetectable viral load through consistent ART cannot sexually transmit the virus. This has been proven by major clinical studies and has significant implications for reducing stigma and improving quality of life.
- Testing strategies: Regular HIV testing is essential for early diagnosis and linkage to care. CDC recommends all adults aged 13 to 64 be tested at least once, and those at higher risk annually. Options include rapid point of care tests, self testing kits, and laboratory based antigen antibody tests with shorter window periods.
Terminology
- HIV
- Human Immunodeficiency Virus; attacks CD4 immune cells.
- AIDS
- Acquired Immunodeficiency Syndrome; advanced stage of HIV infection.
- CD4
- Type of white blood cell targeted by HIV; used to measure immune health.
- Viral load
- Amount of HIV in blood; lower is better for health and prevention.
- ART
- Antiretroviral therapy; medication that suppresses HIV replication.
Quick Revision
- HIV attacks CD4 cells; AIDS is the advanced stage with low CD4 count.
- Transmission occurs via blood, sexual fluids, breast milk, and needles.
- Window period before detection; acute infection has flu-like symptoms.
- ART suppresses virus, prevents progression, and enables undetectable status.
- Global burden remains high, especially in Sub-Saharan Africa.