An HIV-positive patient in Britain has recently become the second person in the world to be cleared of the HIV virus after he received a bone marrow transplant from an HIV resistant donor.

Around three years after he received the bone marrow stem cells from a donor with a rare genetic mutation, that resists HIV infection and more than 18 months after following antiretroviral drugs religiously, the tests show he has no trace of the HIV infection now.

Professor and HIV biologist Ravindra Gupta, who led a team of doctors treating the patient said, “There is no virus there that we can measure. We can’t detect anything”. Gupta also described his patient as “functionally cured and in remission”, but cautioned, “It’s too early to say he’s fully cured”. So he is under observation now.

Ravindra Gupta who is now at Cambridge University started treating the London patient when he was working at University College London.

The patient is popularly known as “the London patient”, because the case is similar to the first known case of a functional cure of HIV in an American man, who was known as the Berlin patient, when he underwent the same kind of treatment in Germany in the year 2007, which cleared his HIV. He has now moved to the United States and is HIV-free.

At present, around 37 million people across the world are infected with HIV and the AIDS pandemic has killed nearly 35 million people across the world since it began in the 1980s. Scientific research into the complex virus has led to the development of drug combinations in recent years that can keep the disease at bay in most patients.

The London patient had contracted HIV in 2003 and in 2012 he was also diagnosed with a type of blood cancer called Hodgkin’s Lymphoma. In 2016, when his cancer becomes unbearable, doctors decided to seek a transplant match for him. “This was really his last chance of survival,” Ravindra Gupta said in an interview to Reuters.

The transplant went smoothly, but there were some side effects, where the patient suffered a period of “graft-versus-host” disease, a condition in which the donor’s immune cells attack the recipient’s immune cells said Gupta, but was later cured.

The London patient, whose case is going to be published in the medical journal Nature soon and whose case was recently presented at a medical conference in Seattle has requested his medical team not to reveal his name, age, nationality or other personal details.