Early, aggressive anti-viral treatment has cured a child that tested positive for HIV at birth, according to clinical researchers the University of Massachusetts.

Doctors at the Mississippi hospital where the infected child was born took the unusual step of treating her faster than most infants born with HIV, suggests that a cure could be possible for the more than 300,000 infants a year worldwide born infected with the deadly virus.

The girl, now two years old, received a high therapeutic dose of a triple-drug anti-viral cocktail in the Mississippi hospital where she was born rather than the typical lower prophylactic dose used for infants. Over the next 18 months, the baby was treated with the triple-drug therapy and her blood was tested for the presence of HIV. There was none.

At the end of 2011, 3.4 million children in the world were living with HIV. A surprising case study of a possible cure in one of those children is exciting medical researchers worldwide.

“The child came to our attention as a high-risk exposure to maternal HIV,” says Hannah Gay, University of Mississippi pediatric infectious disease specialist. The girl’s HIV-positive mother was poor, had no prenatal care, and didn’t get antiviral drugs during pregnancy. Gay decided to test the newborn for HIV and by 30 hours after birth the results showed she was HIV positive. The fact that the newborn tested positive so quickly after birth is a sign she was probably infected in utero, rather than during birth, HIV specialists say.

The mother and child eventually stopped showing up for treatments, and it wasn’t until months later that, with the assistance of Mississippi state health authorities, Gay found the child and mother. The mother said that the child had no anti-viral drugs for the previous six or seven months. Gay expected to find that the child’s blood was teeming with HIV. But surprisingly, tests couldn’t find any virus.

“My first thought was, ‘Oh, my goodness, I’ve been treating a child who’s not actually infected,’” Gay says. But a review of the previous blood work confirmed the child was HIV-positive at birth. Just in case there was a laboratory error on the new blood samples, the tests were redone. “When all those came back negative, I knew something odd was afoot,” Gay says. She contacted Katherine Luzuriaga at the University of Massachusetts, an expert in pediatric HIV/AIDS.

Luzuriaga’s lab and other labs across the country have been performing ultra-sensitive tests on the baby’s blood since that time, August 2012. The tests have been mixed. While pieces of HIV DNA and RNA have been occasionally detected, there has been no evidence that the virus is actively replicating in the child’s cells.

“We think it was that very early and aggressive treatment,” says Luzuriaga, “that curtailed the formation of viral reservoirs.” Once populated with HIV-infected cells, these reservoirs, or hideouts in immune cells, can re-establish infection if medications are stopped. Luzuriaga says researchers have ruled out most other possible reasons for the unexpected cure. The mother did not have a less virulent strain of HIV, and the child does not have known genetic mutations that confer protection against HIV, there is nothing different about the child’s immune system.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, says the child’s cure lends support to something scientists have long believed: that a cure is possible “if you can get somebody treated before the reservoir of virus forms in the body, and before the immune system has been damaged by months or years of viral replication.”

The case holds promise for children infected with HIV globally, 91 percent of them in sub-Saharan Africa. Although the number of children receiving anti-retroviral therapy is increasing, only 28 percent of children that need it are getting it now.

“It’s exciting to us,” Luzuriaga says. “Because if we were able to replicate this, I think it would be very good news.”