By Patricia Reaney

London - Africa's Aids epidemic may not have been fuelled mainly by sexual transmission of the HIV virus but by unsafe medical injections and blood transfusions, a team of international researchers said on Thursday.

The findings contradict widely-held views about how the virus that causes Aids spread through Africa, and could have implications for public health measures to fight the disease.

Most scientists believe heterosexual sex spreads HIV and Aids in up to 90 percent of adult cases in sub-Saharan Africa, home to 30 million of the 42 million people living with the disease.

But a team of eight experts from three countries who reviewed data on HIV infection in Africa estimate that only about a third of adult cases are sexually transmitted.

They said health care practices, especially contaminated medical injections, could also be a major cause.

"The idea that sex explains 90 percent of African HIV just doesn't fit the facts," said David Gisselquist, a Pennsylvania-based independent consultant and member of the research team.

"We need to take a look at the alternate explanations, in particular healthcare transmissions which seems to fit a lot of facts," he added in a telephone interview with Reuters.

The findings, reported in the International Journal of STD & AIDS, a peer-reviewed journal published by Britain's Royal Society of Medicine, were not accepted by all scientists.

"The idea that dirty needles or blood transfusions are the main route for HIV transmission in Africa today, flies in the face of experience on the ground," said Dr Chris Ouma, head of health programmes at the charity ActionAid Kenya.

"In Kenya, medical procedures have largely been made safe but still HIV infections continue to rise."

But Dr George Schmid, of the department of HIV and Aids at the World Health Organisation in Geneva, said it is plausible that unsafe medical injections can cause some HIV cases.

"I think the question is what proportion," he told Reuters.

"We are acutely aware of and concerned about the situation and do want to work with Gisselquist and others to try and resolve the issues as best we can and to come up with a way forward to find out what the true answer is."

The WHO and UNAIDS, the United Nations agency spearheading the global battle against HIV and Aids, will hold a meeting in Geneva on March 13 and 14 to address the issue of unsafe injections.

In three reviews in the journal, HIV specialists including Gisselquist, Francois Vachon of the University of Paris in France, Devon Brewer of the University of Seattle in Washington and others, said the Aids epidemic in Africa has not followed the normal pattern of sexually transmitted diseases (STDs).

In the 1990s in Zimbabwe, overall STDs decreased by 25 percent but HIV infections rose by 12 percent a year despite an increased use of condoms in high-risk groups.

The team argued that the virus is more easily transmitted through unsafe injections and tainted blood transfusions than through heterosexual sex.

They also said surveys have shown sexual activity in Africa is much the same as in North America and Europe where the HIV and Aids infection rates are much lower.

Studies have also identified HIV positive babies whose mothers are not infected, which the researchers said suggests unsafe injections could be a factor.

"Every year there are hundreds of millions of unsafe injections in Africa where needles have been used on someone and re-used without sterilisation," said Gisselquist.

He added that "a growing body of evidence points to unsafe injections and other medical exposures to contaminated blood" as an explanation for the spread of the epidemic.