Human Immunodeficiency Virus (HIV) is a viral infection that targets and weakens the body’s immune system, particularly by attacking CD4 cells (a type of white blood cell) that play a key role in immune defense. The progressive loss of these cells impairs the body’s ability to fight opportunistic infections such as tuberculosis, fungal and bacterial infections, and certain cancers.
The most advanced stage of HIV infection is known as Acquired Immunodeficiency Syndrome (AIDS), which may develop within 2 to 15 years after initial infection, depending on the individual. AIDS is characterised by the presence of specific infections, cancers, or other severe clinical conditions.
For more information, see the 2025 WHO HIV/AIDS factsheet
Sources: HRB