An infant treated with anti-viral drugs now appears to be free of HIV, but it's still conceivable that there was a virus 'hidden away' in the little girl that is undetectable and could be reactivated. NBC's Dr. Nancy Snyderman reports.

The case of a baby who may have been cleared of an HIV infection raises two tantalizing prospects: Is it possible to save even more newborns from infection, and is it possible that other babies may have been cured and no one knows it yet?

One thing that everyone agrees is clear: It's really too soon to say the 2 1/2-year-old from rural Mississippi is actually cured, and it's way too soon to change the standard ways that newborns are now treated to protect them from the virus.

Jim Watson / AFP - Getty Images file Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks during the 19th International AIDS Conference in Washington, D.C., on July 23, 2012.

But researchers are already thinking about ways they can design studies to see if starting a full course of treatment in a newborn can prevent the 200 new HIV infections seen every year in U.S. babies and the more than 300,000 that happen globally.

“This is an important, but small step in the direction of understanding how we might better treat HIV-infected infants,” Dr. Anthony Fauci, who directs the National Institute of Allergy and Infectious Diseases, told NBC News.

The main goal, Fauci points out, is to prevent infection in the first place. Done right, standard procedures protect babies 95 percent of the time. If a woman has the human immunodeficiency virus that causes AIDS, she can start taking a cocktail of drugs right away that prevent her from infecting her baby in the womb or during birth. Newborns are given a light course of drugs, to, just to be sure.

If they get infected anyway, then the babies get a heavier, three-dose cocktail if drugs to keep them healthy.

The Mississippi baby’s case is unusual. Her mother showed up in labor and didn’t know she had HIV. The baby was a little premature, so she was kept in the hospital for longer than normal. That gave Dr. Hannah Gay of the University of Mississippi Medical Center a chance to deliver an unusually intense course of HIV drugs to the child right away.

This drove the infection down to what’s known as undetectable levels, meaning the virus isn’t active. But it’s always still there, waiting to come back unless the patient takes a cocktail of drugs every day. And if the mother hadn’t stopped bringing her baby to the hospital for several months, no one would ever have noticed something usual was happening in her infant’s body.

But she did. The mom disappeared twice, and missed at least eight months worth of treatment. So Gay frantically checked the baby when she did come back, looking to see how bad the infection was. When she couldn’t find any evidence of the virus, she called in help. That’s when other experts found, to their amazement, that there was virtually no trace of the virus left in the child – only apparently harmless bits of genetic material: DNA and RNA.

This case raises the possibility that giving newborns that drug cocktail sooner might not just keep them healthy, but allow them to stop taking the medications altogether someday, said Fauci.

“If the baby does get infected, if you could treat them as early as possible you give yourself a much better chance of actually curing the baby,” Fauci said.

Experts stress that it is vital that parents who have HIV-infected children keep giving them the drugs. Taking kids or adults off the treatment can allow the virus to start replicating and damaging the immune system again.

Dr. Carlos del Rio, an AIDS expert at Emory University in Atlanta and a spokesman for the HIV Medicine Association, says he worries that some parents may stop giving HIV drugs to their children. “I worry about the general message to the public. We don’t have a cure for HIV,” he said.

“People shouldn’t be stopping their therapy Del Rio added. “I call this case a miracle. The great majority of babies in this case, if they had gone that long without treatment, would have had advanced HIV. This case is the exception rather than the rule.”

That said, it’s possible that some children who were treated as babies might be able to safely discontinue the drugs, said Fauci.

“Maybe we have actually been curing some people without even realizing it and we need to carefully look to see if there's virus there,” he said.

“You don't want to just decide you're going to stop therapy in children who are doing well. That would be a big mistake, but you should at least look at the possibility that maybe the virus is now absent or essentially no longer viable in those children.”

Other experts say they’ll be studying ways to change policies in developing countries where the AIDS pandemic is still blazing.

“We think this case has the potential to change the way babies born with HIV are treated,” said Dr. Annette Sohn of amfAR (formerly the American Foundation for AIDS Research). “That means diagnosing them in the first few days instead of waiting a few weeks.”

Sohn, who heads an office in Thailand, says it will require a careful balancing act.

Right now, the main AIDS drug used is AZT, which is available very cheaply and which has few side-effects. It is given to newborns to protect them at about a third of the dose that would be given to them to treat an actual known infection.

The problems doctors have in treating newborns, as opposed to older children, come in testing them for infection and in balancing the benefits of drug treatment against the risks. AZT can cause anemia, so doctors are cautious about giving it to babies who don’t need it.

And HIV doesn’t cause any immediate signs of infection. It takes a while to take up residence in the body, and it takes a while for the body to mount an immune response. Most tests that are used to diagnose infection in people look for antibodies – the immune response to an infection, not the virus itself.

So doctors treating newborns may have to turn to a different test, one that looks for virus.

But Sohn says many clinics already do this. They just wait a few weeks. She thinks it may pay to just speed up the process, testing babies withing hours of birth.

“We are already using these virologic tests and we are already using these medications,” she told NBC News. “I think what we are proposing actually compresses the time frame for testing. We may not necessarily be looking at more testing per se."

She thinks many overseas AIDS programs could do this without spending much more time or money. “You’re either looking at investing up front, from birth, or investing in a lifetime of treatment,” she said.

In 2011, the United Nations AIDS agency UNAIDS reported that 330,000 children had been infected with HIV at birth. “If we can get them diagnosed by 12 weeks of age and started on treatment we can reduce the risk of death by 75 percent. But we are struggling to get these babies diagnosed,” she said.

This case, she said, will raise pressure on the UN and other authorities to step up programs to get pregnant women and their newborns tested earlier.

The picture is a little different in the United States, said Chip Lyons of the Elizabeth Glaser Pediatric AIDS Foundation.

“Most women get good care and are seen and are tested. Their status is known,” he said. But in many developing countries, babies often aren’t even tested until they are six weeks old. This finding, he said, suggests that is far too long to wait.

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