A baby born with the virus that causes Aids appears to have been cured, scientists have announced.
Specialists at a major Aids meeting in Atlanta, Georgia, described the case of a child from Mississippi who is now two and a half and has been off medication for about a year with no signs of infection.
There is no guarantee the child will remain healthy, although sophisticated testing uncovered just traces of the virus's genetic material still lingering.
This is only the world's second reported cure. Scientists believe the findings could be used to treat the many cases of babies born with virus in the developing world, where HIV testing is not a standard part of prenatal care.
HIV testing and treatment is usually given to mothers prior to giving birth in the US, but the mother had received no prenatal care in the rural part of America in which she lived.
The mother only discovered she had the virus while in labour. Usually doctors give the newborn low doses of medication to prevent HIV from taking root, but the rural hospital did not have the liquid available.
Instead this baby was given a cocktail of three drugs already used to treat HIV within 30 hours of its birth.
"I just felt like this baby was at higher-than-normal risk, and deserved our best shot," Dr Hannah Gay, a pediatric HIV specialist at the University of Mississippi, said in an interview.
The baby is now "functionally cured" meaning it is in long-term remission even though there is no guarantee all traces of the virus have disappeared.
Dr Deborah Persaud, a virologist at Johns Hopkins University in Baltimore, said at the Conference on Retroviruses and Opportunistic Infections in Atlanta: "This is a proof of concept that HIV can be potentially curable in infants," reported the BBC.
"You could call this about as close to a cure, if not a cure, that we've seen," Dr. Anthony Fauci of the National Institutes of Health told The Associated Press.
However doctors were keen to stress that prevention was better than cure, and no cure was guaranteed.
"We can't promise to cure babies who are infected. We can promise to prevent the vast majority of transmissions if the moms are tested during every pregnancy," Gay said.
The mother's HIV is being controlled with medication and she is "quite excited for her child," Gay added.
Genevieve Edwards, Director of Health Improvement at Terrence Higgins Trust, said: "In the UK we already have a programme of ante-natal screening for HIV, which means that there are very few babies born with the virus. Expectant mothers with HIV are given anti-HIV treatment during pregnancy which together with a low-risk caesarean and no breastfeeding means their babies have a 98% chance of being HIV negative. But this could be of interest where mothers to be are diagnosed with HIV during labour rather than pregnancy.
"The roll-out of anti-retroviral therapy across the developing world has both saved the lives of individuals living with HIV, and also had a real impact on the rates of mother-to-child transmission. In this context, it would seem that success lies in making antenatal testing available and then giving the drugs to the mother to prevent the child getting HIV, rather than hoping the drugs will cure the baby once born HIV positive. But for those babies born with the virus, this may be significant.”
There has only been one other case of a reported cure, when a patient was given a bone marrow transplant from a donor who had a genetic resistance to the virus.
Two million people die of Aids every year. HIV is estimated to have infected 33 million people worldwide.