Human immunodeficiency virus

Definition

Human immunodeficiency virus (HIV) is a retrovirus that targets the immune system, specifically CD4+ T cells, leading to immunodeficiency.
If untreated, HIV infection can progress to acquired immunodeficiency syndrome (AIDS), characterised by severe immune suppression and opportunistic infections.
Transmission occurs via blood, sexual contact, and from mother to child during childbirth or breastfeeding.
Effective antiretroviral therapy (ART) can control the virus and prevent progression to AIDS.
HIV remains a global public health issue, with significant efforts directed towards prevention, treatment, and research.

Epidemiology

Global prevalence: approximately 38 million people living with HIV (2020).
UK prevalence: around 106,000 people living with HIV (2020).
Higher prevalence in certain groups: men who have sex with men (MSM), Black African communities, and individuals with multiple sexual partners.
Incidence declining due to effective prevention and treatment strategies.
Late diagnosis remains a challenge, with around 42% diagnosed late in the UK (2020).
Universal testing and early initiation of ART are key public health strategies.

Aetiology and pathophysiology

HIV is caused by two types: HIV-1 and HIV-2, with HIV-1 being more common and virulent.
Virus targets CD4+ T cells, macrophages, and dendritic cells.
Integration of viral DNA into host genome leads to chronic infection.
Progressive depletion of CD4+ T cells results in immunodeficiency.
Opportunistic infections and malignancies develop as immune system weakens.
Chronic inflammation and immune activation contribute to morbidity and mortality.
ART suppresses viral replication, preserves immune function, and reduces transmission risk.

Types

HIV-1: most common and widespread type, responsible for the majority of global HIV infections.
HIV-2: less transmissible, predominantly found in West Africa, slower progression to AIDS.

Symptoms

Acute retroviral syndrome: flu-like symptoms 2-4 weeks post-exposure (fever, sore throat, rash).
Asymptomatic phase: lasts for several years with no or minimal symptoms.
Persistent generalised lymphadenopathy: enlarged lymph nodes.
Constitutional symptoms: fever, night sweats, weight loss, fatigue.
Opportunistic infections: oral thrush, tuberculosis, PCP pneumonia.
AIDS-defining illnesses: Kaposi’s sarcoma, CNS lymphoma, recurrent bacterial infections.
Neurological symptoms: cognitive impairment, peripheral neuropathy, HIV-associated dementia.
Gastrointestinal symptoms: chronic diarrhoea, oesophageal candidiasis.
Dermatological manifestations: seborrheic dermatitis, molluscum contagiosum.

Signs

Tests

HIV serology: ELISA for HIV antibodies and p24 antigen, confirmatory Western blot.
HIV RNA PCR: viral load testing for diagnosis and monitoring.
CD4 count: to assess immune function and disease progression.
Complete blood count: to detect anaemia, leukopenia, thrombocytopenia.
Liver function tests: monitor ART toxicity.
Screening for opportunistic infections: TB testing, CMV serology, Toxoplasma serology.
Genotypic resistance testing: to guide ART regimen selection.
Hepatitis B and C serology: co-infections.
Sexually transmitted infection (STI) screening: syphilis, gonorrhoea, chlamydia.
Urinalysis: to detect renal involvement.
Baseline and follow-up metabolic panels: to monitor ART side effects and complications.

Management

Antiretroviral therapy (ART): combination regimens (e.g., NRTIs, NNRTIs, IIs, PIs, INSTIs).
Prophylaxis and treatment of opportunistic infections (e.g., TMP-SMX for PCP).
Monitoring and managing ART side effects: liver toxicity, renal dysfunction, lipid abnormalities.
Regular follow-up: CD4 count, viral load testing, clinical assessment.
Vaccinations: pneumococcal, influenza, hepatitis B.
Psychosocial support: counselling, mental health services.
Education on safe sex practices and reducing transmission risk.
Nutritional support: to address weight loss and malnutrition.
Pre-exposure prophylaxis (PrEP) and post-exposure prophylaxis (PEP) for high-risk individuals.
Substance abuse treatment: if applicable.
Regular dental and ophthalmologic evaluations.
Comprehensive, multidisciplinary approach involving primary care, infectious disease specialists, and support services.

Complications

Opportunistic infections: PCP, TB, CMV retinitis, toxoplasmosis.
Malignancies: Kaposi’s sarcoma, non-Hodgkin lymphoma, cervical cancer.
Neurological complications: HIV-associated neurocognitive disorder, peripheral neuropathy.
Metabolic complications: lipodystrophy, insulin resistance, hyperlipidemia.
Cardiovascular disease: increased risk of myocardial infarction and stroke.
Chronic kidney disease: HIV-associated nephropathy.
Liver disease: from ART toxicity or co-infection with hepatitis B/C.
Psychosocial issues: stigma, depression, anxiety.
Drug resistance: due to non-adherence or inadequate ART.
Persistent immune activation and inflammation despite ART.
Increased susceptibility to common infections.
Bone disorders: osteoporosis, osteopenia.

Prognosis

With effective ART, life expectancy approaches that of the general population.
Early diagnosis and treatment initiation are critical for better outcomes.
Prognosis poorer with late diagnosis, low CD4 count, and high viral load.
Regular monitoring and adherence to ART improve prognosis.
Management of comorbidities and complications essential for quality of life.
Continued research and development of new treatments improve long-term outlook.
Psychosocial support enhances adherence and coping with chronic illness.
Public health interventions reduce transmission and support affected individuals.
Comprehensive, multidisciplinary care essential for optimal outcomes.
Prognosis affected by co-infections, particularly hepatitis B and C.

Key points

HIV is a chronic, manageable condition with effective ART.
Early diagnosis and treatment are critical for preventing complications.
Regular monitoring and adherence to ART are essential for maintaining health.
Comprehensive care includes managing comorbidities and psychosocial support.
Prevention strategies include safe sex practices, PrEP, and PEP.
Continued research and public health efforts are crucial to control the epidemic.
Patient education on transmission risk and ART adherence is vital.
Reducing stigma and supporting affected individuals improves quality of life.
Multidisciplinary approach is key to comprehensive HIV care.
Addressing global health disparities is essential for effective HIV control.

Infection