All signs of HIV disappeared in a 30-year-old woman who was diagnosed with the virus that causes AIDS in 2013, researchers said, raising hopes that she may be one of a handful of people worldwide who has permanently fought off the infection.

The 30-year-old mother, originally from the city of Esperanza in Argentina, has the clinical features of an HIV “elite controller,” meaning her infection has been undetectable for years. It didn’t re-emerge even after she stopped taking powerful drugs to treat it, which is what normally happens, researchers said in a studyslated for publication in the Annals of Internal Medicine.

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Bloomberg reported that the virus did not appear to have integrated into her DNA, creating what is known as a provirus, and extensive testing failed to turn it up anywhere. Researchers said that it is possible that she might have experienced what is known as a “sterilizing cure,” meaning she is no longer carrying a replicating form of the virus.

However, how it happened is a mystery. At least two other HIV patients have also been deemed cured, but both underwent extensive treatment for blood cancer that involved stem cell transplants. The researchers offered no answers as to how the young mother eradicated the virus, but her existence suggests it is possible.

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The virus “was not detected in an elite controller despite analysis of massive numbers of cells from blood and tissues, suggesting that this patient may have naturally achieved a sterilizing cure of HIV-1 infection,” said researchers led by Xu Yu at Boston’s Ragon Institute and Natalia Laufer from the Institute of Biomedical Research in Retrovirus and AIDS in Buenos Aires.

Doctors have tried unsuccessfully for decades to eradicate the virus within patients. While combination drug therapies can suppress it so it’s no longer detectable, the vast majority of patients still have a reservoir that’s reactivated after treatment stops. Finding another person who’s virus-free raises the hope for other ways to wipe out the reservoir and cure more people.

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It’s possible the patient’s initial immune response to HIV led to an abortive infection or that her immune system became better at recognizing and destroying it over time, leaving only remnants of HIV behind, said co-author Sharon Lewin, director of the Peter Doherty Institute for Infection and Immunity at the University of Melbourne.

Since the beginning of the AIDS epidemic, nearly 80 million people have been infected with HIV and 36.3 million people have died from complications of the viral illness. An estimated 37.7 million people were living with HIV in 2020 worldwide.

Progress against AIDS over the past two decades has inspired a commitment by United Nations member states to end the epidemic by 2030. The number of people newly infected with HIV fell to 1.5 million worldwide in 2020, from 3 million in 1997.