The world's leading authorities on HIV are urging persons to stick to proven anti-transmission methods, following the recent publication of an article on antiretroviral treatment and sexual transmission of HIV in the Swiss medical journal Bulletin des médecins suisses.

The Joint United Nations Programme on AIDS (UNAIDS) and the World Health Organisation (WHO) have issued a joint statement in the light of the content of the Swiss publication.

According to the joint statement, the article, published by Switzerland's Federal AIDS Commission "states that HIV positive individuals do not risk transmitting the virus to a negative partner" under three conditions.

These were listed as: "The HIV positive partner has to have had undetectable HIV in the blood for at least six months; there must be strict adherence to his/her antiretroviral regimen; and he/she must be free of any other sexually transmitted infections."

The statement noted that the article indicates that "although available medical and biological evidence does not rule out the possibility of HIV transmission" the Swiss AIDS Commission felt there was "enough information to support" what it had published.

In view of this, UNAIDS and WHO said they strongly recommended a comprehensive package of HIV prevention and this included correct and consistent use of condoms.

The organisations noted that people living with HIV who are following an effective antiretroviral therapy regimen can achieve undetectable viral loads (the amount of virus in a body fluid such as blood, semen or vaginal secretions) at certain stages of their.

However, they said while "research suggests that when the viral load is undetectable in blood the risk of HIV transmission is significantly reduced, this has not been proven to completely eliminate the risk of transmitting the virus.

"More research is needed to determine the degree to which the viral load in blood predictsthe risk of HIV transmission and to determine the association between the viral load in blood and the viral load in semen and vaginal secretions. Research also needs to consider other related factors that contribute to HIV transmission including the presence of other sexuallytransmitted infections."

UNAIDS and WHO underlined the importance of effective and proven HIV prevention methods for all people, regardless of their HIV status.

The statement said that a comprehensive HIV prevention package includes, but is not limited to, delaying sexual debut, mutual fidelity, reduction of the number of sexual partners, avoidance of penetration, safer sex including correct and consistent male and female condom use, and early and effective treatment for sexually transmitted infections.