A 2-year-old Mississippi girl is the first child to be "functionally cured" of HIV, researchers announced Sunday.
Researchers said they believe early intervention -- in this case within 30 hours of birth -- with three anti-viral drugs was key to the outcome.
A "functional cure" is when the presence of the virus is so small, lifelong treatment is not necessary and standard clinical tests cannot detect the virus in the blood.
The finding was announced at the 2013 Conference on Retroviruses and Opportunistic Infections in Atlanta.
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.
"We didn't have the opportunity to treat the mom during the pregnancy as we would like to be able do to prevent transmission to the baby," said Dr. Hannah Gay.
Gay, a pediatric HIV specialist at the University of Mississippi Medical Center, told CNN the timing of intervention in this case, before the baby was diagnosed HIV-positive, may deserve "more emphasis than the particular drugs or number of drugs used."
"We are hoping that future studies will show that very early institution of effective therapy will result in this same outcome consistently," she said on the eve of the conference.
Dr. Katherine Luzuriaga, an immunologist at the University of Massachusetts who worked closely with Gay, called the developments fascinating, including the fact that the toddler was found to have no virus in her blood even after her mother stopped giving her treatment for eight to 10 months.
"This is the very first case in which we've conclusively been able to document that the baby was infected and then after a period of treatment has been able to go off treatment without viral rebound," Luzuriaga told CNN.
Because it was determined the Mississippi mother was HIV-positive, once the baby was delivered, Gay immediately began giving the infant antiretroviral drugs in an attempt to control HIV infection.
"We started therapy as early as possible, which in this case was about 30 hours of age," the physician said. "And because it was a high-risk exposure, I decided to use three drugs rather than one."
Within a couple of days, Gay confirmed that the child was HIV positive. She says the baby had probably been infected in the womb.
The child remained on antiretroviral drugs for approximately 15 months. Her mother then stopped administering the drug for some reason and care was resumed after health officials intervened, Gay said.
Researchers have long known that treating HIV-positive mothers early on is important, because they pass antibodies on to their babies.
"One hundred percent of (HIV-positive) moms will pass those antibodies, but in the absence of treatment, only 30% of moms will transmit the actual virus," Luzuriaga told CNN.
HIV-positive mothers given appropriate treatment pass the virus on in less than 2% of cases, Luzuriaga said.
"So all babies are born antibody positive, but only a fraction of babies born to HIV positive women will actually get the virus, and that fraction depends on whether the mom and baby are getting antiviral prophylaxis (preventative treatment) or not," said Luzuriaga.
Newborns are considered high-risk if their mothers' HIV infections are not under control or if they are found to be HIV-positive when they're close to delivering.
Moving quickly to suppress the virus
Usually, these infants would get anti-viral drugs at preventative doses for six weeks to prevent infection, then start therapy if HIV is diagnosed.
Investigators say the Mississippi case may change that practice because it highlights the potential for cure with very early standard antiretroviral therapy (ART).
ART is a combination of at least three drugs used to suppress the virus and stop the progression of the disease.
But they do not kill the virus. Tests showed the virus in the Mississippi baby's blood continued to decrease and reached undetectable levels within 29 days of the initial treatment.