updated 1/31/2008 1:31:11 PM ET 2008-01-31T18:31:11

Swiss AIDS experts said Thursday that some people with HIV who are on stable treatment can safely have unprotected sex with non-infected partners.

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The Swiss National AIDS Commission said patients who meet strict conditions, including successful antiretroviral treatment to suppress the virus and who do not have any other sexually transmitted diseases, do not pose a danger to others.

The proposal, published this week in the Bulletin of Swiss Medicine, astonished leading AIDS researchers in Europe and North America who have long argued that safe sex with a condom is the single most effective way of preventing the spread of the disease — apart from abstinence.

"Not only is (the Swiss proposal) dangerous, it's misleading and it is not considering the implications of the biological facts involved with HIV transmission," said Jay Levy, director of the Laboratory for Tumor and AIDS Virus Research at the University of California in San Francisco.

Decision up to HIV-negative partner
The Swiss scientists took as their starting point a 1999 study by the U.S. Centers for Disease Control and Prevention, which showed that transmission depends strongly on the viral load in the blood.

The Swiss said other studies had also found that patients on regular anti-AIDS treatment did not pass on the virus, and that HIV could not be detected in their genital fluids.

"The most compelling evidence is the absence of any documented transmission from a patient on antiretroviral therapy," said Pietro Vernazza, head of infectious diseases at the cantonal hospital of St.Gallen in eastern Switzerland and one of the authors of the report.

"Let's be clear, the decision has to remain with the HIV-negative partner," he said.

The studies cited by the Swiss commission did not themselves definitively conclude whether people with HIV and on antiretroviral treatment could safely have unprotected sex without passing on the virus.

In practice the recommendation would affect about a third of HIV patients in Switzerland, Vernazza said, but added that patients and their partners would benefit from greatly increased quality of life, such as being able to have children without fear of passing on the virus.

Levy said there was no safe way of knowing whether a patient with HIV who has no detectable virus in the blood will not transmit the virus. More research into the links between viral load in the blood and the presence of the virus in genital fluid was needed, he said.

'An interesting experiment'
The World Health Organization said Switzerland would be the first country in the world to try this approach.

"There is still some concern that you can never guarantee that somebody will not be infectious, and the evidence I have to say is not conclusive," said Charlie Gilks, director of AIDS treatment and prevention at WHO.

"Many countries in western Europe would regard this as an interesting experiment," he said, adding it was unlikely they would follow suit anytime soon.

"We are not going to be changing in any way our very clear recommendations that people on treatment continue to practice safer sex, including protected sex with a condom, in any relationship," Gilks said.

In any case, of the two million people around the world currently receiving HIV treatment, only a tiny number would receive medical care comparable to that in Switzerland qualifying them to have unprotected sex as suggested by the Swiss, he said.

Even in Switzerland, where some 6,000 people are on antiretrovirals, as little as a third of patients could be considered suitable, Gilks said. The guidelines from the Swiss commission require patients to adhere strictly to their treatment regime and many people do not.

He said WHO was concerned that the Swiss proposal could be misinterpreted to imply that everybody who is on treatment can have unprotected sex.

"It may be fine for Switzerland, it may be fine for a few other countries who have similar small numbers of patients who are very carefully followed up," said Gilks. "But from our point of view globally, we are not going to be changing our recommendations."

Copyright 2008 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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