When news of the Mississippi baby who was "functionally cured" of HIV broke in 2013, a woman in Italy went to her doctors. Much like her own child, the American girl had been born with HIV, and had immediately received antiretroviral therapy following her birth. Now, doctors were announcing that the Mississippi baby had remained virus free for 10 months after stopping the treatment. Aggressive, early intervention had cured her, doctors said. So, when the mother in Italy saw the good news, she asked her child’s physicians to do the same. She wanted her three-year-old off the drugs, and they agreed.

"We thought that we had achieved a cure, since the virus has been absent from the child’s body for three years," says Mario Clerici, an infectious disease researcher at the University of Milan in Italy and the co-author of a case report relating the child’s story in The Lancet today. "So when the mom asked us, we took him off the drugs, because apparently the Mississippi baby had been cured."

Before stopping treatment, the child tested negative for HIV. Even so, two weeks after stopping treatment, the virus was back. "All the world believed that it could be done, that if you started treating kids early, and then took took them off the drugs, you could achieve a cure," Clerici says. "But that’s not the case."

After the child's physicians took him off the drugs, they ran an immune system test — one that the Mississippi child never received, Clerici says. "We did in-depth, sophisticated immune testing, and what we saw was that the virus was still there, hiding." This, the researcher says, means that even when there appears to be no virus in a person's body, it leaves a detectable trace on the immune system.

The Italian child’s condition represents another big blow for researchers who think early, aggressive antiretroviral therapy can rid an infant’s body of HIV, Clerici says. The first one came in July, when doctors announced that the Mississippi baby’s virus had returned after 23 months off therapy. But Yvonne Bryson, a pediatrician at the University of California Los Angeles, doesn’t see it that way. "Staying virus free for 23 months is unheard of," she says, and anything that allows a child to be off drugs for a certain amount of time is an improvement.

Bryson is one of the researchers involved in a federally funded clinical trial in which doctors will give early, aggressive treatment to over 50 babies born with HIV. The trial, she says, will begin recruiting patients within the week. "We did reevaluate the whole clinical trial after the Mississippi baby," she says, "and many people in science and in the cure agenda felt like it was really important that it go ahead."

As for the child in Italy, Bryson says that she isn’t surprised. "I suspect there will be more babies who are treated early, and who see the virus return," she says. The treatment’s success doesn’t just depend on its timing. It's also about what drugs are used, whether they're received in significant enough doses, and how high a child’s viral load — a measure of the quantity of virus in a person — is at birth. In the case of the child in Milan, his viral load was higher at birth than that of the Mississippi child. This indicates that he was probably infected in the womb, instead of during his birth, Bryson says — a detail that may have allowed the virus to become more entrenched in his cells.

Moreover, the Milan baby was given a lower dose of drugs than the Mississippi baby during the first few days of his treatment. In addition, it took three months for his viral load to drop all the way down. "So in this case," she says, "they didn’t reduce the amount of virus in the reservoir as much as in the Mississippi baby."

Regardless of these differences, Clerici thinks that the clinical trial shouldn’t take place. "Ethically I don’t think they will be able to do it because both the Mississippi child and this one aren’t saved," he says. "I think they’ll have to put the trial on hold."

The Mississippi baby wasn't the only "functionally cured" child in the US. In March, researchers announced that a baby girl in Long Beach had received early treatment, and was now in remission. She had not yet been taken off antiretroviral therapy, however. "The results from the time that we reported in March have not changed, and the child is still considered ‘functionally cured,’" says Audra Deveikis, the pediatrician who first diagnosed the baby with HIV. But news of the child in Italy is "a major concern," she says, because "it tells us that there’s a lot of stuff about HIV that we don’t know." For now, there are no plans to stop the Long Beach baby's treatment.

"We are learning more with each case," Bryson says, and no one expects to see a lot of cases with the same results. "It will take time," she says, but "we’re still thinking that some cases might have an even better result than the Mississippi baby."