In 2013, doctors delivered a life-altering diagnosis to a woman in Esperanza, Argentina: She had acquired HIV, the virus that causes AIDS. Eight years later, the virus has all but disappeared from her system.
In fact, stunned researchers were unable to find evidence of any HIV viral particles in her body, "despite analysis of massive numbers of cells from blood and tissues, suggesting that this patient may have naturally achieved a sterilizing cure," they wrote on Nov. 16 in the journal Annals of Internal Medicine. However, they cautioned that science cannot definitively prove that no trace of the human immunodeficiency virus remains.
Related: The 12 deadliest viruses in history
This represents the second known case of a person's immune system eliminating HIV without a bone marrow transplant or drug intervention, according to STAT. The first such case was a California woman named Loreen Willenberg, who in 2020 found out that the virus was absent from her body for the first time in 27 years, The New York Times reported. Just two other people — pseudonymously known as the London Patient and the Berlin Patient — have ever been cured of HIV, but only after having their immune cells completely replaced via stem cell therapy, according to research published in 2020 in The Lancet.
The Argentine woman was dubbed the "Esperanza Patient" by her doctors in order to protect her anonymity in a country where people are still stigmatized for HIV-positive status. Medical professionals say that she belongs to a rare group of HIV patients called "elite controllers." Although the virus is present in these folks' systems, they are able to maintain a low enough viral load that they don't develop symptoms, even without treatment.
Elite controllers represent just 1% of the global HIV-positive population, according to research published in 2019 in the Journal of Virus Eradication. Scientists aren't exactly sure how their immune systems eliminate the virus — at least, not yet.
"I'm very keen to learn more about this seemingly new phenomenon of extraordinary elite control," Rowena Johnston, director of research at amfAR, The Foundation for AIDS Research, told NBC News.
For now, Willenberg and the Esperanza Patient are special cases, even among elite controllers. But their very existence offers a glimmer of hope in the ongoing search for an HIV/AIDS cure, doctors say.
"This makes us hopeful that a natural cure of HIV is actually possible," Xu You, a viral immunologist at the Ragon Institute in Boston and one of the lead investigators of the study, told Medscape. "That's the beauty of the name, right?" In addition to being the name of the patient's hometown, "Esperanza" means "hope" in Spanish.
Meanwhile, the patient is expecting her second child and she is reportedly enjoying her HIV-free life. But she wants to make sure others living with HIV have a second chance as well. "Just thinking that my condition might help achieve a cure for this virus makes me feel a great responsibility and commitment to make this a reality," she told STAT in an email.
Originally published on Live Science.