HIV/AIDS researchers have announced progress towards new ways of treating and preventing infection, and have found some new clues to the virus's origins.

The findings were presented last week at the 13th Conference on Retroviruses and Opportunistic Infections in Denver, United States.

Researchers described how a candidate drug called MK-0518 substantially reduced virus levels in 80 per cent of HIV-infected people in a trial in Brazil.

In another study, a drug called tenofovir, which is already used to treat people with HIV, is being combined with another called FTC to see if it can also protect people from being infected in the first place.

The conference also heard new evidence supporting the theory that HIV evolved from the simian immunodeficiency virus that infects chimpanzees (SIVcpz).

Earlier research had suggested this but too few infected chimpanzees were found to investigate it further. Now, researchers have discovered that there are more than 30 strains of SIVcpz, and were stunned to find that in some areas the virus infects up to 35 per cent of the chimpanzee population.

The researchers say two of these strains are genetically closer to HIV than any other known virus.

Link to full article in Science