A patient in London is HIV-free, doctors announced this week in what appears to be an astounding case.

A patient who was diagnosed with HIV in 2003 has become the second patient ever known to be cured of the infection that affects close to 37 million people worldwide after receiving a bone marrow transplant intended to treat cancer, doctors say. The patient received the stem cell transplant from a donor with a rare CCR5 mutation that allows HIV resistance in May of 2016 to treat his Hodgkin’s lymphoma.

The London patient, who is remaining anonymous, also underwent chemotherapy. He took antiretroviral therapy drugs for HIV until September of 2017, doctors say. His drug regiment was much less harsh than the only other known patient who was cured of HIV.

He has been HIV-free, in remission, for 18 months, according to tests.

In a research letter set to publish Tuesday in the peer-reviewed journal Nature, doctors who treated him say this proves that the Berlin patient cured of HIV in 2007 wasn’t an anomaly and HIV remission is possible.

“Everybody believed after the Berlin patient that you needed to nearly die basically to cure HIV, but now maybe you don’t," said Dr. Ravindra Gupta, a virologist at University College London who presented the findings at a conference in Seattle, The New York Times reports.

The first patient to be cured of HIV, Berlin patient Timothy Ray Brown, underwent two bone-marrow transplants also for cancer treatments, took a cocktail of drugs and experienced serious complications that put his life in danger. At one point, doctors induced a coma. He survived the ordeal, coming out of it without HIV. Over a decade later, he is still considered cured. Treatments that have tried to replicate Brown's result in other HIV patients have failed, until now.

Gupta's team says the London patient's treatment isn't conventional for all HIV patients, but does offer hope for future HIV and AIDS treatments.

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