This brings the current count to seven. The patient is a 60-year-old German man who prefers to remain anonymous. The man received a stem cell transplant in 2015 to cure leukaemia, which also rendered the virus undetectable in tests.

This is the same method used with other individuals who have become HIV-free. For these transplants, individuals with a specific genetic mutation in their immune system that suppresses HIV are chosen. This mutation is particularly found in a small percentage (about 1%) of people with Northern European genes.

Researchers cannot be absolutely certain that the man is "cured," as HIV can "hide" in the body in a dormant state, making the virus undetectable. However, the person has lived without HIV medication for years, and the virus has not reappeared in tests, which researchers describe as "promising." A person in whom HIV is undetectable cannot transmit the virus.

Notably, in the treatment of the anonymous German, the stem cell donor had a less pronounced genetic mutation than the donors in the other cases. This genetic mutation occurs in about 16% of people with Northern European genes, which, according to researchers, increases the potential number of stem cell donors for this procedure. "We need to understand how the new immune system successfully grafted into his body and how it successfully eliminated HIV reservoirs over time," the researchers said.

Although, like the other six patients, HIV can no longer be detected in this person, this does not indicate a potential vaccine against HIV. A stem cell transplant is an expensive and risky operation, used only as a last resort, for example, in leukaemia patients. People with HIV can suppress the virus through medication, making a stem cell transplant unnecessary for them.

In 2009, Timothy Ray Brown, also known as the "Berlin patient," was the first person who researchers believed was cured of HIV. Since then, there have been six others who seem to have been "cured," including now the unknown "Berlin patient II."