Scientists in search of a cure for AIDS say they have been inspired, not deterred, by the recent relapses of two HIV positive patients believed to have been cured of the virus.

Last month, the two “Boston patients” who had received bone marrow transplants seemingly removing the virus from their bodies found they had relapsed, and were forced back into antiretroviral treatment.

However, according to The Globe and Mail, leading experts at the University of California are saying the disappointment could now pave the way towards a greater understanding of HIV for future research.

Steven Deeks, a professor and HIV expert said: “It’s a setback for the patients, of course, but an advance for the field because the field has now gained a lot more knowledge.”

The main message, according to Mr Deeks, is that tests designed to detect even very low levels of HIV in the body now need to be far more sensitive.

The two men, who have not been identified, had lived with HIV for about 30 years.

They both developed lymphoma, a cancer, which required a bone-marrow transplant.

After the transplant, there was no detectable HIV in the blood for two years in one patient and four in the other.

The pair came off their anti-retroviral drugs earlier this year.

In December, however, the news came that one of the men had begun to show signs of an HIV rebound by August, while the second patient had relapsed in November.

One of the doctors of the Boston patients, Timothy Henrich, said the return of the virus emphasised how difficult it can be to detect HIV inside the body.

He said: “Through this research we have discovered the HIV reservoir is deeper and more persistent than previously known and that our current standards of probing for HIV may not be sufficient.”

It is difficult to get rid of HIV because it hides inside human DNA, forming untouchable reservoirs in the body.

Dr Michael Brady, medical director at Terrence Higgins Trust, the UK’s largest HIV and sexual health charity, said: “A bone marrow transplant is a complex and expensive procedure, which comes with significant risks. For most people with HIV, it would be more dangerous to undergo a transplant than to continue managing the virus with daily medication.

“While this is by no means a workable cure, it does give researchers another sign-post in the direction of one. Until a cure is found, we urge people to continue using condoms and testing for HIV if they’ve put themselves at risk.”

Gay, bisexual, and other men who have sex with men (MSM) continue to be disproportionately affected by the spread of HIV in the UK; accounting for almost half of all new cases in 2011.