A leading U.S. AIDS researcher says that the reported cure of a baby born with the virus that causes the deadly disease could hold promise for the treatment of infants in the developing world, but not until more research is done.

The director of the National Institute of Allergy and Infectious Diseases, Anthony Fauci, said Monday that the significance of the recovery of a two-year-old girl in southern state of Mississippi might be minimal at best for adults, but more pronounced for babies in cases where their mothers have not been treated for their HIV infections.

"I would say the applicability might be indirect for adults, but more direct for children, particularly for children born in an environment, such as in the developing world, where mothers not infrequently come in without any treatment for their own HIV infections, which puts the baby at a much greater risk to get infected," he said.

Dr. Fauci called the success in the treatment of the Mississippi girl a "proof of concept" that "very early and aggressive treatment" can be beneficial, but not necessarily proof of successful treatment on a broader basis until clinical testing is done.

"So again," he added, "it's a proof of concept that one might be able to now in the proper fashion, with proper ethical controls, to see in a clinical study, whether you can actually on a broader scale replicate this."

In the Mississippi case, treatment on the infant was started within a day of her birth, a rapid reaction rarely available for adults infected with HIV.

"Adults, by the time know they're infected, they've usually gone anywhere from several weeks to years before they know they're infected," he said, explaining that, within that timeframe, the virus has already established a strong reservoir in the patient's body, making it much, much more difficult to cure or eradicate.

"Compared to what we now see in this single case of the infant," he added, "the treatment was started very quickly before the virus had the opportunity to establish a big reservoir, and certainly before the virus had the opportunity to destroy the immune system."

Doctor Hannah Gay of the University of Mississippi Medical Center reported the breakthrough, believed to be only the world's second reported cure of the deadly virus. Doctors say the baby is "functionally cured," meaning the virus cannot be detected with standard tests and lifelong treatment is not necessary. It is the first case of an infant achieving a functional cure.

According to Gay, she initially thought that perhaps the girl was being needlessly treated.

"My first thought was to panic," said Gay. "I thought, 'Oh my goodness, I have been treating a child who is not actually infected.'"

The unidentified girl was born HIV-positive to a mother who received no prenatal care and was not diagnosed as HIV-positive herself until just before delivery. Had the mother known her condition sooner, she could have received drugs that would have prevented transmission to the baby.

The baby remained on antiretroviral drugs for about 15 months. Her mother then, for some reason, stopped administering the drug.

After receiving no treatment for 10 months, the toddler was brought back to her doctor, who ordered standard blood tests to see how the child was faring before resuming antiviral therapy.

Two subsequent tests failed to find any detectable levels of HIV. And tests for HIV-specific antibodies, the standard clinical indicator of HIV infection, also remained negative.

The results were announced Sunday at the Conference on Retroviruses and Opportunistic Infections in Atlanta.