Abstract
BackgroundHIV surveillance requires monitoring of new HIV diagnoses and differentiation of incident and older infections. In 2008, Switzerland implemented a system for monitoring incident HIV infections based on the results of a line immunoassay (Inno-Lia) mandatorily conducted for HIV confirmation and type differentiation (HIV-1, HIV-2) of all newly diagnosed patients. Based on this system, we assessed the proportion of incident HIV infection among newly diagnosed cases in Switzerland during 2008-2013.Methods and ResultsInno-Lia antibody reaction patterns recorded in anonymous HIV notifications to the federal health authority were classified by 10 published algorithms into incident (up to 12 months) or older infections. Utilizing these data, annual incident infection estimates were obtained in two ways, (i) based on the diagnostic performance of the algorithms and utilizing the relationship ‘incident = true incident + false incident’, (ii) based on the window-periods of the algorithms and utilizing the relationship ‘Prevalence = Incidence x Duration’. From 2008—2013, 3’851 HIV notifications were received. Adult HIV-1 infections amounted to 3’809 cases, and 3’636 of them (95.5%) contained Inno-Lia data. Incident infection totals calculated were similar for the performance- and window-based methods, amounting on average to 1’755 (95% confidence interval, 1588—1923) and 1’790 cases (95% CI, 1679—1900), respectively. More than half of these were among men who had sex with men. Both methods showed a continuous decline of annual incident infections 2008—2013, totaling -59.5% and -50.2%, respectively. The decline of incident infections continued even in 2012, when a 15% increase in HIV notifications had been observed. This increase was entirely due to older infections. Overall declines 2008—2013 were of similar extent among the major transmission groups.ConclusionsInno-Lia based incident HIV-1 infection surveillance proved useful and reliable. It represents a free, additional public health benefit of the use of this relatively costly test for HIV confirmation and type differentiation.
Highlights
The prevalence of HIV infection is relatively high in Switzerland
Annual incident infection estimates were obtained in two ways, (i) based on the diagnostic performance of the algorithms and utilizing the relationship ‘incident = true incident + false incident’, (ii) based on the window-periods of the algorithms and utilizing the relationship ‘Prevalence = Incidence x Duration’
Incident infection totals calculated were similar for the performance- and window-based methods, amounting on average to 1’755 (95% confidence interval, 1588—1923) and 1’790 cases, PLOS ONE | DOI:10.1371/journal.pone
Summary
The prevalence of HIV infection is relatively high in Switzerland. Between 0.3% and 0.5% of the Swiss adult population were infected with HIV in 2012, and there were 16’000–27'000 persons alive with HIV [1]. The epidemic started in the 1970s, and the cases notified to the Swiss Federal Office of Public Health (SFOPH) rose rapidly after HIV screening had been introduced in 1985. Between 2009 and 2013, the notifications generally decreased for all groups, but with a transient 15% increase in 2012 for both MSM and HET [2]. This renewed increase was an object of great concern to those involved in the HIV prevention campaign
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