However there are many caveats to this story.

1. Even though their tests do not show a presence of HIV in his system, doesn’t mean it’s not there. This virus is known for hiding well and popping up later. It’s been seen before in patients taking anti-retroviral drugs. It is possible that if more sophisticated tests were used on this patient, they would detect the virus that is still in his body. So it’s still not entirely clear that he is HIV-free.

2. The chances of finding a bone marrow donor with two copies of this genetic mutation for everyone one of the 33 million people worldwide living with HIV or AIDS is not realistic because only one percent of Caucasians and zero percent of African Americans or Asians have this particular genetic mutation.

3. Bone marrow transplants are dangerous for patients. Before they can get the donated stem cells that will replace their own, they have to take strong chemotherapy to destroy their own bone marrow — leaving them without an immune system to fight off any disease — until the transplanted bone marrow can make new blood cells. Plus patients run the risk of rejecting the new cells, which means they have to take immune-suppressing drugs for the rest of their life.

4. Bone marrow transplants are very expensive and not an option for many people living with this disease around the world.

Both the doctors in Berlin and AIDS experts we’ve spoken with say this is a “proof of principle.” “It’s an interesting case for researchers,” according to Dr. Rudolf Tauber, from the Charite hospital in Berlin, where the patient was treated. The hope is that this one case could lead to future treatments. Dr. Gallo says, “If patients living with HIV and AIDS have access and can adhere to today’s retroviral therapy, many will live longer, healthier lives, perhaps full length lives.”