A London man has been declared virtually free of the HIV virus.  The treatment was rare, expensive, and difficult, but it shows that defeating the HIV virus is possible.

"There is no virus there that we can measure," said Professor Ravindra Gupta, the HIV biologist who co-led a team of doctors treating the unidentified patient, "We can't detect anything."  Gupta says the patient is "functionally cured" and "in remission".  But he added this caveat:  "It's too early to say he's cured."

The "London patient", as he is known,has not had an easy time of it.  He contracted HIV in 2003, and was also diagnosed with Hodgkin's lymphoma in 2012 .

"This was really his last chance of survival," Gupta said.

The patient received a bone marrow stem cell transplant from a donor with a genetic mutation called CCR5 delta 32 which makes him resistant to HIV.  Three years after the transplant and 18 months after coming off of retroviral drugs, the man's blood underwent extremely sensitive testing and showed no trace of the virus.

This is the only the second time a person has been cleared of the HIV virus.  The first was American Timothy Brown, who underwent a similar genetic treatment in Germany in 2007.  He is still HIV-free