Human immunodeficiency virus (HIV) is a single-stranded ribonucleic acid (RNA) virus recognized as the causative agent of acquired immunodeficiency syndrome (AIDS)
Types of HIV epidemics:
Low-level epidemic is when HIV may have existed for many years but has never spread to significant levels in any sub-population; recorded infection is largely confined to high-risk individuals (eg drug injectors, sex workers, men having sex with other men [MSM]); HIV prevalence has not consistently exceeded 5% in any sub-population
Concentrated HIV epidemics is when HIV has spread rapidly in a defined sub-population but is not well established in the general population; HIV prevalence is consistently >5% in at least one sub-population but is <1% in pregnant women in urban areas
Generalized HIV epidemic is when HIV is firmly established in the general population; HIV prevalence is consistently >1% in pregnant women
Epidemiology
Globally, as of the end of 2023, reported cases to the World Health Organization (WHO) were approximately39.9 million with the African region being the most severely affected with 1 in every 30 adults (3.4%) living with HIV and accounting for > 2/3 of the people living with HIV
An estimated 0.6% (0.6-0.7%) of adults aged 15-49 years worldwide are living with HIV
There have been 42.3 million (35.7-51.1 million) deaths reported to the WHO globally as of 2023 with 630,000 deaths due to HIV-related causes
In the Philippines, people living with HIV were estimated at 140,000 in 2021, at 520,000 in Thailand in 2021, at 540,000 in Indonesia in 2021, and at 87,581 (77,910-98,007) in Malaysia in 2019
A cumulative total of 10,785 HIV cases in Hong Kong have been recorded in 2020, with the median age of 37 years (30-39 years old in males; 40-49 years old in females) and are mostly male (83%)
Pathophysiology
The outer viral membrane which contains HIV-specific glycoproteins (gp) including gp120 and gp41, facilitates attachment and entry of HIV into the host's CD4+ cells
CD4+ T cell destruction is the hallmark of HIV infection
Viral replication progresses with the presence of two key enzymes: Reverse transcriptase and integrase
Reverse transcriptase: Forms viral RNA to viral DNA
Integrase: Transports viral DNA into the nucleus to integrate with human chromosomal DNA
B cell proliferation and abnormal antibody production impairs humoral immunity
Ongoing viremia with pro-inflammatory cytokines, B cell proliferation, and hypergammaglobulinemia leads to a chronic inflammatory state that contributes to cardiovascular disease, cancer, and other chronic diseases
