Model Answer
0 min readIntroduction
Acquired Immunodeficiency Syndrome (AIDS) is a chronic, potentially life-threatening condition caused by the Human Immunodeficiency Virus (HIV). First recognized in the early 1980s, AIDS has become a global pandemic, affecting millions worldwide. HIV attacks the body’s immune system, specifically CD4+ T cells, weakening the body’s ability to fight off infections and certain cancers. Understanding the structure of the virus, its transmission pathways, the disease’s progression, and effective prevention strategies are crucial for controlling this epidemic. As of 2022, an estimated 39 million people were living with HIV globally, highlighting the continued importance of addressing this health challenge.
Structure of the HIV Pathogen
HIV is a retrovirus, meaning it uses RNA as its genetic material and employs an enzyme called reverse transcriptase to convert RNA into DNA. The structure of HIV is complex and consists of the following key components:
- Envelope: The outer layer derived from the host cell membrane during budding. It contains embedded glycoproteins, primarily gp120 and gp41, which are crucial for viral entry into host cells.
- Capsid: A conical core composed of p24 protein, which encloses the viral RNA and enzymes.
- Genome: Two identical strands of RNA, carrying the genetic information for viral replication.
- Enzymes: Essential for viral replication, including:
- Reverse Transcriptase: Converts viral RNA into DNA.
- Integrase: Integrates the viral DNA into the host cell’s genome.
- Protease: Cleaves viral polyproteins into functional proteins.
The gp120 protein on the viral envelope binds to the CD4 receptor on host cells (primarily CD4+ T cells), initiating the infection process. gp41 facilitates the fusion of the viral envelope with the host cell membrane.
Transmission of HIV
HIV is transmitted through specific bodily fluids that contain sufficient concentrations of the virus. The primary modes of transmission include:
- Sexual Contact: Unprotected vaginal, anal, or oral sex with an infected individual. This is the most common mode of transmission globally.
- Blood Transfusion: Receiving contaminated blood or blood products. This risk is significantly reduced in developed countries due to rigorous screening procedures.
- Sharing Needles: Injecting drug users who share needles and syringes.
- Mother-to-Child Transmission: During pregnancy, childbirth, or breastfeeding.
- Occupational Exposure: Healthcare workers accidentally exposed to infected blood or body fluids.
HIV is not transmitted through casual contact, such as hugging, shaking hands, sharing utensils, or using the same toilet.
Pathogenesis of AIDS
The pathogenesis of AIDS is a multi-stage process:
- Acute Infection: Following infection, there is a period of acute HIV infection, characterized by flu-like symptoms. During this phase, the virus replicates rapidly, leading to a high viral load and a decline in CD4+ T cell counts.
- Clinical Latency: The virus enters a state of clinical latency, where it continues to replicate at a lower level. Individuals may remain asymptomatic for years, but the virus continues to damage the immune system.
- AIDS: As CD4+ T cell counts fall below 200 cells/µL, the individual becomes susceptible to opportunistic infections and cancers, defining the stage of AIDS. Common opportunistic infections include Pneumocystis pneumonia, Kaposi’s sarcoma, and tuberculosis.
The virus primarily targets CD4+ T cells, but can also infect other immune cells, leading to a progressive decline in immune function. The depletion of CD4+ T cells impairs the body’s ability to mount an effective immune response against pathogens.
Prevention of AIDS
Preventing HIV transmission involves a combination of strategies:
- Safe Sex Practices: Consistent and correct use of condoms during sexual activity.
- Testing and Counseling: Regular HIV testing and counseling to identify infected individuals and provide appropriate care.
- Antiretroviral Therapy (ART): ART suppresses viral replication, reducing the viral load and preventing transmission. "Undetectable = Untransmittable" (U=U) is a key concept.
- Needle Exchange Programs: Providing sterile needles and syringes to injecting drug users.
- Prevention of Mother-to-Child Transmission (PMTCT): ART for pregnant women with HIV, elective Cesarean section, and avoidance of breastfeeding.
- Pre-Exposure Prophylaxis (PrEP): Taking ART medications before exposure to HIV to reduce the risk of infection.
- Post-Exposure Prophylaxis (PEP): Taking ART medications after potential exposure to HIV to prevent infection.
Conclusion
HIV/AIDS remains a significant global health challenge, but advancements in understanding the virus, its transmission, and pathogenesis have led to effective prevention and treatment strategies. Continued efforts in research, prevention programs, and access to ART are crucial for controlling the epidemic and improving the quality of life for people living with HIV. The focus should be on reducing new infections, providing comprehensive care for those infected, and ultimately, achieving an AIDS-free generation.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.