Real-time imaging in lab monkeys has pointed to the havens where HIV lurks after being beaten back by drugs, scientists said on Monday.

The achievement may provide a powerful weapon in the quest for an AIDS cure, they hope.

Antiretroviral drugs bring the human immunodeficiency virus (HIV) down to levels that, using conventional methods, are undetectable.

But the virus is a stealthy foe. In retreat, it holes up in a small number of cells in certain tissues -- and when treatment is stopped, it rebounds.

In a paper published in the journal Nature Methods, researchers reported a groundbreaking way to identify these "reservoirs" among rhesus monkeys which had been infected with the simian equivalent of HIV.

A team led by Francois Villinger at Emory University in Atlanta in the US state of Georgia tagged the virus with an antibody that sticks to a viral surface protein.

The antibody itself had been tagged with a short-lived radioactive isotope of copper that is commonly used in medical scans.

A positron emission tomography (PET) scanner was then brought into play, spotting the radioactive telltales in real time.

It showed that the virus was present in the colon, lymph nodes, small bowel, genital tract and spongey bones in the nasal passages.

"Before we can hope to eliminate reservoirs of infected HIV cells, we must first identify tissue sites that can possibly serve as these viral reservoirs," Villinger said in a press release.

"We believe we can now do this more effectively in our animal models and that this strategy can translate these non-invasive techniques into investigating the eradication of HIV infection and targeting of virus reservoirs in humans."

Attacking HIV's last redoubts is the goal set in 2010 by Nobel laureate Francoise Barre-Sinoussi, who co-identified the AIDS virus.

Despite progress, the work remains at an early stage as scientists wrestle with understanding the viral reservoirs and the enduring problem of virus mutation.

A main avenue of approach is so-called kick-and-kill -- to flush the virus out and then destroy it with drugs -- which means identifying the boltholes is a vital step.

Close similarities between primates mean that monkeys and simian HIV are excellent substitutes in the lab for humans and our version of the virus.

Since 1981, about 78 million people have been infected by HIV, according to the UN programme UNAIDS.

Thirty-nine million have died from AIDS-related illnesses.