ATLANTA, GA — On Sunday, March 3, doctors announced that for the first time in history, a baby had been cured of an HIV infection, a surprising development that could lead to changes in the treatment of infected newborns, and dramatically reduce the number of children living with the virus, which causes AIDS.

The doctors, led by researchers from Johns Hopkins Children’s Center, say the baby, who was born in rural Mississippi, was treated aggressively—beginning about 30 hours after birth—with antiretroviral drugs, a procedure that normally does not take place.

If the report is confirmed, it would boost international support for research directed at finding a cure for HIV/AIDS, something that was thought to be virtually impossible only a few years ago. Some experts caution that the findings in a baby may not be relevant to adults.

The infant (whose name and gender were not disclosed) would be the world’s second well-documented case of a cure for HIV. The first was Timothy Brown, known as the “Berlin patient,” a leukemia patient who received a bone-marrow transplant from a donor who was genetically-resistant to HIV infection.

On Monday, March 4, Dr. Deborah Persaud, Associate Professor at the Johns Hopkins Children’s Center and lead author of the report on the child, presented the researchers’ findings—which have not yet been published in a peer-reviewed medical journal—at the Conference on Retroviruses and Opportunistic Infections in Atlanta.

According to Dr. Persaud, the child’s mother arrived at a Mississippi hospital already in labor during the fall of 2010, and gave birth prematurely. The mother had not seen a doctor during her pregnancy and was unaware that she was HIV-positive. The hospital transferred the baby, then approximately 30 hours old, to the University of Mississippi Medical Center, where Dr. Hannah Gay, an associate professor of pediatrics, ordered two blood tests for the presence of the HIV virus’ RNA and DNA.

Although a newborn with an infected mother is usually given one or two drugs as a preventive measure, Dr. Gay ordered a three-drug regimen devised for treatment, not prevention.

On Monday, the researchers presented five positive tests (four for viral RNA, and one for DNA) from the baby’s first month of life. The research indicates that once the treatment started, the HIV levels in the child’s blood declined in a pattern that is characteristic of infected patients.

With the treatment, virus levels rapidly declined and were undetectable by the time the newborn was a month old. When the baby was 18 months old, the mother stopped giving the baby drugs.

When she examined the child five months later, Dr. Gay tested the baby and the results were negative, although the pediatrician says she expected to see high viral loads in the baby.

Dr. Gay contacted researchers, including Dr. Persaud, who were conducting a study sponsored by the Foundation for AIDS Research. They put the baby through a battery of sophisticated tests, and found tiny amounts of viral genetic material, but no virus that is able to replicate.

On Monday, Dr. Persaud said there was little doubt that the baby—who is now 2 ½ years old—had experienced a “functional cure.” The child has reportedly been off drugs for a year and shows no signs of a functioning virus.

After the presentation, some experts suggested that the drugs given to the Mississippi baby killed off the virus before it could establish a hidden reservoir. The study findings could result in a new protocol for the immediate testing and treatment of newborns.

Transmission of the virus from mother to child is rare in the U.S. (with only about 200 reported cases a year), because infected mothers are typically treated during pregnancy.

But women in developing countries are less likely to be treated during pregnancy. And in Africa and other places that lack sophisticated testing, babies born to infected mothers are often not tested until after they are six weeks old.

In the past, there have been reported cases of babies clearing the virus, even with no treatment, including one reported in 1995 in The New England Journal of Medicine. But the tests have gotten more sophisticated in the past two decades. Studies are planned to see if early testing and aggressive treatment will now work for other babies.

The United Nations estimates that 330,000 babies were newly infected with HIV in 2011, the most recent year for which data is available, and that there are more than three million children globally living with HIV. If further research determines that the Mississippi treatment works in other babies, it will almost certainly be recommended internationally.

The bone marrow transplant that cured the Berlin patient, a middle-aged man, is a difficult and life-threatening procedure, but the Mississippi treatment is not, and its widespread application could lead to a new standard of care.