Acquired Immunodeficiency Syndrome (AIDS)

AIDS (Acquired Immunodeficiency Syndrome) is a contagious disease caused by the HIV virus, characterized by severe weakening of the immune system. It is marked by opportunistic infections and certain types of cancer. First identified in the 1980s, it has affected millions of people worldwide and has become a global health issue.

Historical Background

AIDS was first recognized in 1981 in the United States, among young and otherwise healthy men presenting with rare opportunistic infections such as Pneumocystis jirovecii pneumonia and Kaposi’s sarcoma. The disease was initially stigmatized with names like “gay male syndrome,” but in 1983, Luc Montagnier and his team identified HIV as the causative agent, establishing its scientific definition. In the same year, Robert Gallo demonstrated that the virus belonged to the retrovirus family and targeted CD4+ T lymphocytes. The first ELISA test was developed in 1985, enabling screening of blood donations. By the late 1980s, it became clear that HIV/AIDS was not limited to high-risk groups but could also spread through heterosexual contact.

The Relationship Between HIV and AIDS

HIV (Human Immunodeficiency Virus) is a lentivirus belonging to the retrovirus family. Its entry into host cells begins when the viral surface glycoprotein gp120 binds to the CD4 receptor. This binding is followed by viral fusion mediated by the coreceptors CCR5 or CXCR4, allowing HIV genetic material to integrate into the host cell. As a result, CD4+ cells are driven into apoptosis or destroyed by cytotoxic T cell responses.

The annual average decline of CD4+ T cells by 50–100 cells/mm³ leads to progressive immune system weakening. When the CD4 count falls below 200 cells/mm³, the condition is classified as AIDS. At this stage, individuals become vulnerable to opportunistic infections (such as tuberculosis, candidiasis, CMV, and toxoplasmosis) and malignancies (such as Kaposi’s sarcoma and non-Hodgkin lymphoma).

Epidemiology and Global Spread

According to UNAIDS 2023 data, 39 million people worldwide are living with HIV. Since the outbreak began in the 1980s, more than 85 million people have been infected with HIV, and approximately 40 million have died from AIDS-related causes. Currently, about 1.3 million new infections and 630,000 HIV-related deaths are reported annually.

HIV prevalence exceeds 5% in Sub-Saharan Africa; in countries such as Eswatini, Lesotho, and Botswana, it reaches up to 20%. While new case numbers remain stable in high-income countries, they are rising in Eastern Europe and Central Asia due to stigma and inadequate testing infrastructure.

Routes of Transmission

Sexual Transmission: Anal intercourse carries the highest risk (1–3%), vaginal intercourse carries a risk of 0.1–0.2%, and oral intercourse carries a risk of 0.01%.

Blood Transmission: Transmission through needle sharing has a risk of 0.67–0.85%; transmission via blood transfusion carries a risk exceeding 90%.

Vertical Transmission: In untreated HIV-positive mothers, transmission risk can reach up to 25%; with ART during pregnancy, it drops below 1%.

Clinical Course and Stages

1. Acute HIV Infection (Primary Infection)

2. Chronic Infection (Asymptomatic Stage)

3. AIDS Stage

Neuropathogenesis and Effects on the Nervous System

HIV is one of the few viruses that infect the central nervous system. The virus infects microglia and astrocytes, triggering neuroinflammation. Chronic inflammation leads to synaptic dysfunction and neuronal degeneration, resulting in the spectrum of HIV-Associated Neurocognitive Disorders (HAND):

• HIV-associated dementia (HAD): 10–15% prevalence
• Mild neurocognitive disorders: 30–50% prevalence
• Mechanisms: Increased cytokines such as TNF-α and IL-6, oxidative stress, mitochondrial dysfunction.

Diagnostic Methods

Fourth-generation antigen/antibody combination tests

HIV RNA (PCR) test

Western blot or immunoblot

CD4 count and viral load monitoring

Treatment Approaches

Antiretroviral therapy (ART) consists of drug combinations that suppress HIV:

• Success rate: Over 90% viral suppression
• Timing of initiation: Recommended at time of diagnosis
• Impact on life expectancy: With ART, life expectancy of HIV-positive individuals can equal that of HIV-negative individuals
• Side effects: 5–10% lipodystrophy, 1–3% hepatotoxicity

New developments:

• Long-acting injectables (e.g., cabotegravir)
• Pre-exposure prophylaxis (PrEP)
• Post-exposure prophylaxis (PEP)

Prevention Strategies

Global and national strategies to prevent HIV/AIDS transmission encompass both individual protective measures and public awareness and service access initiatives.

Protective Methods (Condom Use):

• Correct and consistent condom use provides effective protection against HIV and other sexually transmitted infections (STIs), especially recommended for individuals with multiple partners and high-risk groups.

Pre-Exposure Prophylaxis (PrEP):

• A preventive approach involving regular antiretroviral medication for HIV-negative individuals to significantly reduce the risk of HIV infection. Current FDA and WHO-approved PrEP regimens are increasingly widely used among high-risk populations (e.g., individuals with HIV-positive partners, men who have sex with men, sex workers).

Post-Exposure Prophylaxis (PEP):

• A 28-day antiretroviral treatment protocol initiated within 72 hours after potential HIV exposure (e.g., unprotected sexual contact or needlestick injury). Rapid initiation is critical for effectiveness.

Needle Exchange Programs:

• Programs providing sterile injection equipment to drug users effectively reduce the spread of HIV and hepatitis through bloodborne transmission. These programs may also include counseling, testing, and referral to treatment services.

ART During Pregnancy:

• Antiretroviral therapy administered to HIV-positive pregnant women reduces mother-to-child transmission (vertical transmission) risk to below 1%. Mode of delivery, breastfeeding policies, and neonatal prophylaxis are integral components of this strategy.

Public Education and Test Access:

• Large-scale HIV awareness campaigns, combined with anonymous and free testing services, enhance early diagnosis and treatment opportunities. Target populations for education include youth, high-risk groups, and healthcare workers.

Social Impacts and Stigma

HIV is not only a medical condition but also a disease with profound social consequences. HIV-positive individuals frequently face stigma, exclusion, and discrimination, leading to psychological issues at the individual level and public health challenges at the societal level.

Social Isolation:

• Studies show that 30–50% of HIV-positive individuals are ostracized or excluded from social circles. This can lead to loneliness, depression, and suicidal ideation.

Discrimination in Employment:

• More than 25% of HIV carriers face discrimination, job loss, or career barriers in the workplace, undermining their economic independence.

Barriers to Health Services:

• Stigma can delay testing, diagnosis, and initiation of treatment. This not only harms individual health but also negatively impacts viral transmission within the community.

Impact on Public Health:

• Stigmatization remains one of the greatest obstacles in combating HIV/AIDS. Hidden cases, delayed diagnosis, irregular treatment, and increased transmission risk directly undermine the effectiveness of epidemic control efforts.

Situation in Türkiye

The first case in Türkiye was identified in 1985.

As of 2023, according to Ministry of Health records, over 35,000 individuals in Türkiye are HIV-positive. The actual number is likely higher due to undiagnosed cases. Regarding transmission routes, more than 80% of cases are attributed to sexual contact; injection-related transmission is low.

Treatment and Monitoring: Antiretroviral therapy (ART) is covered by the Social Security Institution. Individuals diagnosed with HIV receive free treatment in state hospitals.

Early detection efforts continue through prenatal screening, premarital testing, and routine blood donation screening. Stigma remains a significant public health barrier. However, social support initiatives are being carried out through civil society organizations and counseling centers.

Current Status and Future Perspectives

Modern medicine has made significant advances in HIV treatment and prevention strategies. In the 2020s, scientific research on the concept of a “cure” has accelerated.

Sterilizing Cure Research:

• Approaches aiming for complete eradication of HIV from the body include gene editing technologies (e.g., CRISPR-Cas9), bone marrow transplantation, and cellular immune modification. To date, only a few individuals have been reported to have achieved complete HIV clearance (e.g., the Berlin and London cases).

Functional Cure:

• The virus remains in the body but is maintained at suppressed levels, allowing the individual to remain free of disease without ongoing treatment. This approach is linked to therapies aimed at re-educating the immune system.

HIV Vaccine Development:

• mRNA-based HIV vaccines have rapidly entered clinical trials following the success of COVID-19 vaccines. Candidates with high neutralizing antibody capacity show particular promise. No licensed HIV vaccine currently exists.

UNAIDS 2030 Target:

• The Joint United Nations Programme on HIV/AIDS (UNAIDS) aims to end the HIV/AIDS epidemic by 2030. This goal is based on key milestones: a 90% reduction in transmission, 95% of diagnosed individuals receiving treatment, and universal viral load suppression.