An 18-year-old is in remission from HIV despite not having taken any drugs to fight the virus for 12 years.

Doctors presented the case, which is the first reported long-term remission from HIV in a child, at a conference in Vancouver.

It is believed that the French girl was infected either at the end of her mother’s pregnancy or during childbirth itself.

For a month after the birth, she was given a drug designed to prevent the infection from taking hold of her system.

However, as soon as the medicine was withdrawn the patient developed high levels of the human immunodeficiency virus.

The treatment was changed to a cocktail of four strong anti-HIV drugs, which the girl received for six years until her family withdrew treatment.

Doctors at the time registered an "undetectable viral load" in her system, the International Aids Society (IAS) conference was told.

The girl was recently re-discovered by French doctors, who were surprised to learn that - 12 years later - the teenager is still in remission.

She is not believed to be one of the so-called "elite controllers", who are naturally capable of controlling HIV infection.

The remission is explained by the early treatment by a combination of antiretroviral drugs shortly after the infection. 

The case proves the effectiveness of early treatment of HIV in both children and adults, said Dr Asier Saez-Cirion of the Institut Pasteur in Paris.

Experts say studies are needed to determine why some patients can continue to control the virus after stopping treatment.