HIV

HIV (human immunodeficiency virus) attacks the immune system, specifically CD4 cells (T cells), which are essential for fighting infections. Without treatment, HIV gradually weakens the immune system and can lead to AIDS (acquired immunodeficiency syndrome).

HIV is spread through certain body fluids including blood, semen, vaginal fluids and breast milk. The most common routes of transmission are unprotected sex and sharing needles.

Modern combination antiretroviral therapy (ART) means that most people living with HIV can expect a near-normal life expectancy when diagnosed and treated early. Effective treatment also prevents transmission to others.

Fourth-generation HIV tests detect both HIV antibodies and the p24 antigen, enabling earlier detection than antibody-only tests. Most infections can be reliably detected from 45 days after exposure. Regular testing is recommended for anyone at increased risk.

Causes of HIV

HIV is caused by the human immunodeficiency virus, which belongs to the retrovirus family. The virus targets CD4 T-lymphocytes, gradually depleting the immune system's ability to fight infections and certain cancers.

Transmission routes include:

Unprotected vaginal, anal or oral sex with an infected person
Sharing needles or other injecting equipment
Mother-to-child transmission during pregnancy, birth or breastfeeding
Occupational exposure through needlestick injuries (rare)

HIV cannot be transmitted through everyday contact such as kissing, sharing cutlery, coughing or touching. Pre-exposure prophylaxis (PrEP) is available on the NHS and is highly effective at preventing HIV infection in people at higher risk. A person with HIV on effective treatment who has an undetectable viral load cannot pass the virus to sexual partners.

Tests that can help check this condition

Learn more on the official NHS page .

Medical review

Dr. Shahzaib Ahmad MBBS, BSc, MRCP, FRCA, FFICM

Clinical Supervisor - Vitall|GMC 7495062|Profile

Dr Shahzaib Ahmad is a Consultant in Intensive Care Medicine with subspecialty experience in cardiac critical care and neurocritical care. He has extensive experience managing complex acute and cardiovascular conditions in hospital intensive care settings. Dr Ahmad supports Vitall in reviewing health content for clinical accuracy and alignment with current medical practice.

Reviewed on 22/05/2026

Next review due 22/05/2027

Review focus: Blood biomarkers, laboratory testing methodology, and biochemical interpretation.

This content has been reviewed for medical and scientific accuracy but does not replace advice from a qualified healthcare professional.