Only half of people on HIV treatment fit 'Swiss Statement' criteria for non-infectiousness in US study

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A study of a sample of predominantly African-American people with HIV in the US has found that, in those taking antiretroviral therapy (ART), only 51% met the criteria for non-infectiousness set by the Swiss Statement of January 2008.

This study (published in HIV Medicine), though small, underlines other findings that African Americans are missing out on the benefits of ART. The high proportion of people with detectable virus while on ART in this study was apparently driven by poor adherence, but may have been amplified by a high rate of untreated sexually transmitted infections (STIs).


The Swiss Statement said that people who have had an undetectable viral load (below 40 copies/ml) for at least six months, who have no sexually transmitted infections, and who have their adherence regularly monitored by their physician, can be regarded as non-infectious. The statement became regarded as a landmark in the development of giving treatment to suppress viral load as an HIV prevention strategy, as well as for the treatment of individuals.

Researchers from the University of Connecticut, who pioneered the study and development of programmes to change HIV risk behaviour, recruited 228 people living with HIV from local STI clinics through community sampling.



detectable viral load

When viral load is detectable, this indicates that HIV is replicating in the body. If the person is taking HIV treatment but their viral load is detectable, the treatment is not working properly. There may still be a risk of HIV transmission to sexual partners.

risky behaviour

In HIV, refers to any behaviour or action that increases an individual’s probability of acquiring or transmitting HIV, such as having unprotected sex, having multiple partners or sharing drug injection equipment.

Swiss statement

A 2008 article by a group of Swiss doctors which asserted that people living with HIV who are taking antiretroviral therapy and have an undetectable viral load, with no sexually transmitted infections, do not pass on HIV to their sex partners. Since then, major scientific studies have proven that the statement was correct.


A serodiscordant couple is one in which one partner has HIV and the other has not. Many people dislike this word as it implies disagreement or conflict. Alternative terms include mixed status, magnetic or serodifferent.

statistical significance

Statistical tests are used to judge whether the results of a study could be due to chance and would not be confirmed if the study was repeated. If result is probably not due to chance, the results are ‘statistically significant’. 

Ninety-one per cent of the people in the study were African American, 54% defined as gay men, 24% were heterosexual men and 22% were women. Their average age was 45. This was a socially deprived group: no less than 73% had been in prison at some point in the past year, and 61% earned less than $10,000 a year (£6265).

One criterion was that they had to have drunk alcohol in the past week, as this is part of a research programme looking into the influence of alcohol in risk behaviour, but alcohol intake turned out not to be one of the factors that influenced infectiousness. Twenty-two per cent had a drink more than one day a week and only 11 people four or more days a week; 12% had five or more drinks when they did drink.

Viral load and adherence

Eighty-one per cent (185) of people were taking ART. The only demographic factor associated with being on ART was that people who managed to avoid prison during the year were 2.8 times more likely to be on ART than people who had been incarcerated.

Of people on ART, 25% had a detectable viral load at the beginning of the study and 15% at the end of it a year later, with a third having a detectable viral load at least once. Twenty-four per cent had an STI during the past year. Adding these together meant that only 51% of people on ART fitted the Swiss Statement criteria for non-infectiousness for the year of the study. The only demographic characteristic associated with having an undetectable viral load was being married: more than twice as many people who were married had an undetectable viral load than people who were unmarried.

Adherence was measured by ‘unannounced pill count’, which meant participants were phoned up randomly and asked to count their pills over the phone. It was 86% in those with an undetectable viral load and 79% in people who were detectable; 32% and 37% respectively had adherence of below 85%. This may not sound like a big difference but it was strongly statistically significant; people with adherence below 85% were 18 times more likely to have a detectable viral load at one of the two time-points.

Risk behaviour and viral load beliefs

Evidence that receiving ART was associated with increased sexual risk behaviour was ambiguous. Just under half of the people receiving ART reported sex with partners with a negative or undetectable viral load (in the last four months) and only 26% of those not receiving ART; statistically, people on ART were 2.7 times more likely to have serodiscordant sex than people not on ART. On the other hand, people on ART were no more likely to report unprotected sex with serodiscordant partners (29 vs 26%, odds ratio 1.13). People on ART were twice as likely to report having had an STI (24 vs 12%) although this failed to be statistically significant (p=0.1).

One of the more worrying findings of the survey was that one in four people thought their viral load was other than it was. Although this included people who were not infectious by Swiss Statement criteria when they thought they were, people with a detectable viral load who thought they were undetectable were more common, with a third of people with detectable viral load believing they were undetectable at the start of the study. Thus had gone down to one in five people a year later.

The researchers comment: “The Swiss Statement unambiguously specifies the circumstances under which a person with HIV should be considered non-infectious.

“Unfortunately, these conditions do not reflect the realities of many people living with HIV.”


Kalichman SC et al. Assumed infectiousness, treatment adherence and sexual behaviours: applying the Swiss Statement on infectiousness to HIV-positive alcohol drinkers. HIV Medicine DOI: 10.1111/j.1468-1293.2102.01062.x. 2012.