Medical researchers have made a major breakthrough in the fight against HIV, with a fifth person now confirmed to be in remission from the virus.

The 53-year-old man, referred to as the “Düsseldorf patient,” is the latest to be cured of HIV after a risky stem cell transplant. He joins four other people who have been cured of the virus, including the “London patient” who is now virus-free after a similar procedure.

The patient received a stem cell transplant from a donor with a genetic mutation that makes them resistant to HIV. The procedure was part of a research study conducted by the University of Cologne and the University Hospital of Düsseldorf.

The study’s lead researcher, Professor Gero Hütter, said the patient has now been free of HIV for 18 months and is showing no signs of relapse.

“We are delighted to have achieved this result and that the patient is doing so well,” Professor Hütter said.

The patient is the first person to be cured of HIV without the use of antiretroviral drugs. While this type of stem cell transplant is not a viable option for the majority of HIV patients, the researchers hope their findings could lead to new treatments for the virus.

“This is an exciting development and a major step forward in the fight against HIV,” said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. “We are hopeful that this breakthrough will open the door to new treatments and a potential cure for HIV.”