The Federal Health Office has launched a pioneering study that questions people who test HIV positive about the circumstances of their infection.
Aids specialists believe that by examining new reported cases of HIV – and specifically the time of infection – they can improve prevention.
"This questionnaire will help us to pinpoint and understand the number of new infections," said Pietro Vernazza, head of the project.
Vernazza, an Aids expert from the cantonal hospital in St Gallen, told swissinfo the information from the study will enable experts to understand the epidemic’s evolution in Switzerland and improve existing preventive measures.
"At the moment if we have 750 positive test results annually, we don’t know whether only ten per cent of these have been acquired this year or 50 per cent," he added. "We will have an answer to this important question."
The three stages
The Swiss government will fund the SFr300,000 ($230,000) survey, which runs from July 1 this year until June 30, 2006. It will then take three to six months to collate the information before publication.
Vernazza explained that the first stage of the voluntary and anonymous study involves doctors going through roughly ten questions with each patient who tests positive for HIV over the next year.
This is the regular two-page Federal Health Office survey that has been in place for nearly two decades.
"They will be asked whether they know or have an idea when and where they were infected," said Vernazza.
"We will also want to know whether this infection occurred while this person was already under the influence, as it were, of the HIV prevention campaign."
The project leader believes that a person who grew up in a country where Aids is endemic and was infected there cannot be reached by the Swiss prevention campaign – "so we should not count this HIV infection as a failure of our prevention campaign".
All patients will then be given a longer questionnaire by their doctor, asking about their knowledge of HIV prevention, what they know about safe sex, what they would consider dangerous and what they know about risky behaviour.
In the third and final stage, patients whose test results reveal that they have been infected within the past six months are to be asked whether they are willing to attend a personal interview to examine their infection history in even greater detail.
Vernazza estimates only up to 30 patients will agree to a one-on-one interview.
Ups and downs
Despite effective retroviral treatment and high-profile prevention campaigns – condom use in high-risk situations, for example, has risen from eight per cent in 1987 to over 60 per cent today – the number of new reported cases is at best stable.
According to statistics from the Federal Health Office, the number of reported positive HIV cases peaked at 2,144 in 1991, gradually fell to a low of 581 in 2000, bounced up to 792 in 2002 and then fell again, with 741 cases reported last year.
The problem with these figures, as Vernazza points out, is that they don’t tell us about the new infections. "That’s what we want to find out," he told swissinfo.
"Personally I think new infections are going down and that we are seeing more new HIV test results in people who have come in from abroad who are already positive."
"I believe the Stop Aids campaigns are working – but I would like to show that what I believe is true."
swissinfo, Thomas Stephens
Since 1983 there have been 8,023 cases of Aids reported in Switzerland. Of those infected, 5,531 have died.
Since 1985 there have been 27,904 HIV positive test results in Switzerland.
In 2004, 300 new cases of Aids and 741 new cases of HIV were reported.
20 million people around the world have died from Aids since 1981.
The new survey will run from July 1 this year until June 30, 2006. It will be based on responses from those who test HIV positive at the 11 authorised laboratories.
Participation of the people concerned is voluntary.
The cantonal hospital of St Gallen, the Swiss Aids Federation and the Association of Cantonal Health Officers are also taking part.
The government-funded programme costs SFr300,000.