The results are being presented at the IAS Conference on HIV Science.
There have been two other examples of early, limited treatment leading to outcomes like the one seen in this child, Rizza said, including the case of a baby in MS who received treatment just hours after birth and later went into remission for 27 months. After receiving a burst of treatment soon after being born, the child has since been free of any symptoms or active signs of the menacing virus without any further treatment.
More than half of people infected with HIV worldwide are now getting drugs, and AIDS-related deaths have nearly halved since 2005, putting the world on track to hit the target of 30 million people on treatment by 2020, the United Nations said last week.
Rizza said cases like the child in South Africa are "interesting" and worthy of study, but still unclear at this point.
Scientists hope the case will help improve their understanding of HIV and pave the way for new drugs or vaccines which can cure the infection.
Now, she is nine years old and received 40 weeks of antiretroviral therapy (ART) as a baby before doctors stopped all the treatments to see if her immune system would fend off the infection on its own.
The youngster was first enrolled in the National Institute of Allergy and Infectious Diseases (NIAID)-funded Children with HIV Early Antiretroviral Therapy (CHER) clinical trial in 2007.
Once this was achieved, some continued taking oral treatment as maintenance while the rest were shifted onto the prototype, injectable ARV, administered every four or eight weeks.
"Relapse is a possibility in any case of remission", underlined study co-leader Avy Violari, University of the Witwatersrand, Johannesburg said. "We don't really know what is the reason ..."
Further phase 3 trials of the treatment are already in progress and more evidence will be needed in wider groups of patients but the results from the LATTE-2 study on long-acting therapy could well be the "next revolution in HIV therapy", researchers said. However, a follow-up analysis of the stored blood samples taken over this period indicates that the virus hasn't returned.
ART not only stops HIV from replicating and attacking a patient's immune system, but also curbs its spread to sexual partners.
Injecting drug use accounted for 27 new cases, while there were three cases of mother-to-child transmission. Last week, the United Nations warned that countries must halt the rise of AIDS drug resistance to prevent a swell in new infections and deaths and spiralling treatment costs. When the drug treatment ended, the virus was undetectable in has blood - and has since remained so without the child having to take anymore of these drugs.
Two similar cases have been reported of long-term HIV remission in a child after early, limited treatment with antiretroviral drugs.