The Swiss Statement and its repercussions

There is evidence (see above) of some groups of gay men knowing, from the late 1990s onwards, that people with an undetectable HIV viral load were much less infectious, and were using this knowledge in sexual decision-making. Public discussion of this became much more high profile after a paper was issued by the Swiss Federal Commission for HIV/AIDS in January 2008.

The authors of the ‘Swiss Statement’ have since said that they were surprised at the amount of attention their paper got and the global discussion it set off. It was intended purely as an in-country guideline directed at doctors and, significantly, at legal professionals. Much of the motivation for the statement lay in the fact that Switzerland had prosecuted and convicted a number of HIV-positive people for exposing partners to HIV, and the doctors wanted there to be a statement saying that HIV-positive people posed no risk to their partners if they were undetectable on stable antiretroviral therapy. They stated that unprotected sex between a positive person on antiretroviral treatment, and without an STI, and an HIV-negative person did not comply with the criteria for an “attempt at propagation of a dangerous disease” in the Swiss penal code nor for “an attempt to engender grievous bodily harm”.

Although the statement purely concerns the position of individuals and was not connected with the mathematical-modelling studies that were starting to be issued which looked at the possibility of using viral control as a prevention measure, it was significant because it transformed the discussion around viral undetectability and infectiousness from one in which using viral load status to inform sexual-risk decisions was seen as dangerous, and a rationalisation for having unprotected sex, to one in which it became possible to talk about its legitimate use as a prevention measure.

Nonetheless, the statement caused widespread concern amongst some prevention and public health advocates who felt it was based on weak evidence in some areas and risked undermining people’s efforts to maintain and promote condom-based safer sex.    

The statement said that people with HIV are not sexually infectious (“ne transmettent pas le VIH par voie sexuelle”), as long as the following conditions are met:

  • The HIV-positive individual takes antiretroviral therapy consistently and as prescribed and is regularly followed by his/her doctor.
  • Viral load is 'undetectable' and has been so for at least six months.
  • The HIV-positive individual does not have any STIs.

The original statement made no distinction between vaginal and anal sex, though all the evidence the writers cited in support of the statement concerned heterosexual transmission, such as the Rakai study, and they have since said that the statement only covered heterosexual transmission.1

The statement had five co-authors, four of them Switzerland’s foremost HIV experts: Professor Pietro Vernazza, of the Cantonal Hospital in St Gallen, and President of the Swiss Federal Commission for HIV/AIDS; Professor Bernard Hirschel from Geneva University Hospital; Dr Enos Bernasconi of the Lugano Regional Hospital; and Dr Markus Flepp, President of the Swiss Federal Office of Public Health’s Sub-committee on the clinical and therapeutic aspects of HIV/AIDS. Significantly, its fifth author was a community activist, François Wasserfallen of the European AIDS Treatment Group, thus ensuring that community ‘buy-in’ for the statement was present from the start.

The headline statement says that “after review of the medical literature and extensive discussion” the Swiss Federal Commission for HIV/AIDS resolves that, “An HIV-infected person on antiretroviral therapy with completely suppressed viraemia ('effective ART') is not sexually infectious, i.e. cannot transmit HIV through sexual contact.”

The Commission states that an HIV-positive person in a stable relationship with an HIV-negative partner, who follows their antiretroviral treatment consistently and as prescribed and who does not have an STI, is "not putting their partner at risk of transmission by sexual contact".

However, they emphasise that, "Couples must understand that adherence will become omnipresent in their relationship when they decide not to use protection, and due to the importance of STIs, rules must be defined for sexual contacts outside of relationship."

They add that heterosexual women will have to consider eventual interactions between contraceptives and antiretrovirals before considering stopping using condoms. They also say that insemination via sperm washing is no longer indicated when "antiretroviral treatment is efficient."

The Commission goes on to say that it "is not for the time being, considering recommendations that HIV-positive individuals start treatment purely for preventative measures." Aside from the cost involved, they argue, it cannot be certain that HIV-positive people would be sufficiently motivated to follow, and apply to the letter, antiretroviral treatment on a long-term basis without medical indications. They note that poor adherence is likely to facilitate the development of resistance, and that, therefore, antiretroviral therapy as prevention is indicated only in "exceptional circumstances for extremely motivated patients".

The Commission also says that their statement should not change prevention strategies currently taking place in Switzerland. With the exception of stable HIV-positive couples where HIV-positivity and the efficacy of antiretroviral therapy can be established, measures to protect oneself must be followed at all times. "People who are not in a stable relationship must protect themselves," they note, "as they would not be able to verify whether their partner is positive or on efficient antiretroviral therapy."

At a meeting in Mexico City in August 2008,2 Pietro Vernazza clarified some aspects of the statement. “We never thought of it as a statement that was to be delivered worldwide,” he said, but rather “it was meant only to be delivered to Swiss physicians to help them discuss sexual risk-taking with their patients and their steady partners.” He regretted the “ne transmettent pas” in the statement’s title and said that this absolute phrasing was ‘misleading’ in that it appeared to rule out the possibility of any residual risk.

 “We also made it clear that the only person who can assess perfect adherence and regular check-ups would be a steady partner, and that it should only be the informed [HIV-negative] partner who could assess the risks for themselves.” The statement, he said, was “good news for a small number of people, but [for everyone else] prevention messages remain unchanged”.

Nonetheless, he defended the applicability of the statement at least to heterosexual couples in the light of subsequent research, including the Wilson paper in The Lancet,3 which said that gay male couples where the HIV-positive partner was on treatment could reduce their transmission risk to virtually zero if they also used condoms, and said the estimated residual risk to heterosexual couples where the HIV-positive partner was on treatment was of the same order as other possible, but unlikely, hazards such as the risk of dying in an air crash or avalanche.


  1. Hirschel B Undetectable = Uninfectious? Treatment as Prevention. Presentation for Community Seminar, BHIVA Autumn Conference. See, 2008
  2. Vernazza P Presentation in HIV Transmission under ART. Symposium session SuSat41, seventeenth International AIDS Conference, Mexico City, 2008
  3. Wilson DP et al. Relation between HIV viral load and infectiousness: a model-based analysis. The Lancet 372: 314-320, 2008
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