Adam Castillejo has been cured of HIV according to doctors, having gone 30 months without antiretroviral therapy and still free from the virus.

He was, however, not cured as a result of taking retroviral drugs but by a stem-cell treatment he received for cancer according to the Lancet HIV.

Doctors believe the donors of those stem cells have an uncommon gene that gives them protection against HIV.

Therefore, with their gene now replacing 99% of Adam Castillejo’s gene, he is now free of the disease.

Stem-cell transplants appear to stop the virus from replicating inside the host’s body by replacing the patient’s immune cells with donors’ cells that resistant to HIV.

It’s more than one year now since 40-year-old Adam Castillejo was declared free from the virus. Still, he has no detectable active HIV infection in his blood, semen or tissues, his doctors say – despite not taking retroviral drugs throughout that time.

Meanwhile, 99% of his cells are HIV resistant while his 1% gene still has traces of the virus according to doctors.

In 2011, Timothy Brown became the first person doctors claimed was cured of HIV, three and half years after having the same stem cell transplant.