US researchers have identified a preventative measure against HIV that could dramatically reduce the number of new cases in high risk areas such as sub-Saharan Africa.

Tenofovir is an antiviral drug that is currently used in combination medications given to HIV patients.

Is is being trailed on HIV negative participants of groups who are considered at high risk of contracting the virus, including gay and bisexual men, sex workers and drug users.

Tenofovir is one of the group of drugs known as nucleotide analogue reverse transcriptase inhibitors (nRTIs).

The results of the five studies taking place in four continents will not be available until early 2008.

However, scientists using computer modelling technology have predicted several outcomes based on the efficiency of the drug and the likeliness of people taking it regularly.

While cautious of over-stating its effects, it is possible that one pill per day of Tenofovir, manufactured by California pharmaceuticals company Gilead Sciences under the brand name Viread, could keep millions of people healthy.

They found that the best-case scenario in sub-Saharan Africa could be a reduction of 30 million new cases of HIV over the course of a decade.

Previous testing on monkeys has been successful in preventing the infection with simian immunodeficiency virus (SIV), the strain of the virus contracted by primates.

There were 24.5 m cases of HIV recorded in Sub-Sahara Africa, according to the Report on the global AIDS epidemic 2006.

“If you do it right, you can prevent lots of infections,” Dr. John Mellors, who helped direct the study, told Reuters.