An HIV-positive woman appears to have been cured of the infection without any medical intervention, doctors said on Tuesday (NZ time).
If confirmed, doctors say it could help develop a sterilising cure - one that doesn't just keep illness at bay, but eliminates it from the body completely.
The woman - dubbed the 'Esperanza Patient' in a nod to the first person ever cured of the disease, 2008's 'Berlin Patient' - was diagnosed with HIV-1 in 2013. HIV-1 is the most common form of the HIV virus, accounting for 95 percent of all infections.
Eight years on, no trace of the virus can be found in her system, the American College of Physicians reported on Tuesday (NZ time). If confirmed, she would be just the second person ever to have fully defeated the virus naturally.
The Ezperanza Patient is just the fourth known case to be cured of HIV, which can lead to AIDS and has killed more than 36 million people since first appearing in humans in the early 20th century.
The infection is particularly difficult to fight because even if its symptoms and spread are controlled via antiretroviral therapy (ART), the virus can lay low and launch a counter-attack if the treatment ever stops.
What's got scientists excited is the evidence suggests the Esperanza Patient's immune system "developed a sterilising cure" on its own somehow. The first two cured patients - the Berlin Patient and 2019's 'London Patient' - both underwent a bone marrow stem cell transplant to treat cancer, and were cured of their HIV infections in the process.
Their donors had a rare genetic mutation. Known as 'elite controllers', these people - about 1 percent of all patients - have a natural resistance to HIV, and can keep their infection under control without having to use ART.
The Berlin Patient - later identified as Timothy Brown - suffered a number of severe side-effects from his operation, which led doctors to warn against relying on bone marrow transplants as a treatment.
The only other person to apparently have eliminated the virus is a California woman in her 60s, who was diagnosed as HIV-positive in 1992 but in 2020 had no trace of it left.
The Esperanza Patient's boyfriend at the time she was diagnosed was also HIV-positive, and died of AIDS in 2017. She only took ART briefly in 2019 while pregnant, and discontinued it after giving birth to a healthy baby.
More than 1.5 billion cells of hers were examined over four years, researchers finding nothing.
"These observations raise the possibility that a sterilising cure may be an extremely rare but possible outcome of HIV-1 infection," the study, published in the Annals of Internal Medicine, concluded - with a caveat.
"Does this imply that our patient has developed a sterilising cure during natural infection? We believe this is likely, but it cannot be proved."
