Scientists and doctors have been amazed and bewildered by an Argentinian woman who seems to have naturally 'cured' herself of HIV.
She's the second person in history to have this occur and medical professionals reckon it opens up a slim hope for the millions of people around the world living with the virus.
The South American woman, who is known only as Esperanza patient, was diagnosed with HIV in 2013, however eight years later, she has no disease-causing or 'intact' virus in her blood.
It follows a similar case that was discovered in August last year, with Loreen Willenberg, 67, from San Francisco revealed to have 'cured' herself of HIV naturally.
A group of Harvard-based scientists have announced the Argentinian woman's case during a large meeting of international HIV experts this week.
Dr Natalia Laufer, the patient's doctor, said (via The Times): "Finding one patient with this natural ability for functional cure [no virus that can reproduce] is good, but finding two means so much more.
"It means there must be more people like this out there. This is a significant leap forward in the world of HIV cure research. Upon diagnosis, her tests surprised us all."
Researchers believe the two cases are an extreme example of a rare category called 'elite controllers', who are HIV-positive people who manage to not have active traces of the virus in their blood despite not taking any antiretroviral medication.
Some experts reckon elite controllers have unique immune system cells that allow them to do this, however genetic studies have been done and they don't have any obvious mutations that would suggest they have better immune systems.
Normally, HIV will get into the DNA of a cell, where it's able to replicate and slowly destroy the body. But with elite controllers, the virus, for some reason, nestles into an area of the genome where it doesn't do anything.
Professor Xu Yu, a HIV researcher from the Harvard Medical School, said: "The level of functioning virus in these patients is at least 1,000 times less than a patient who is on HIV drug therapy."
During their presentation this week, the Harvard scientists say the case in Argentina sheds more light on elite controllers and they will be using her outcome to see if they can replicate it in a lab.
It's hoped that if they can somehow manage to do that, then it could pave a new way forward in the fight against a virus that tens of millions of people live with and many more try to avoid.
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