Human immunodeficiency virus (HIV) is a retrovirus that can lead to acquired immunodeficiency syndrome (AIDS), a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections.

What are the early symptoms of HIV infection?

Many people do not develop any symptoms when they first become infected with HIV. Some people, however, get a flu-like illness within three to six weeks after exposure to the virus. This illness, called Acute HIV Syndrome, may include fever, headache, tiredness, nausea, diarrhoea and enlarged lymph nodes (organs of the immune system that can be felt in the neck, armpits and groin). These symptoms usually disappear within a week to a month and are often mistaken for another viral infection.

During this period, the quantity of the virus in the body will be high and it spreads to different parts, particularly the lymphoid tissue. At this stage, the infected person is more likely to pass on the infection to others.

More persistent or severe symptoms may not surface for several years, even a decade or more, after HIV first enters the body in adults, or within two years in children born with the virus. This period of "asymptomatic" infection varies from individual to individual. Some people may begin to have symptoms as soon as a few months, while others may be symptom-free for more than 10 years. However, during the "asymptomatic" period, the virus will be actively multiplying, infecting, and killing cells of the immune system.