The Role of Migration and Domestic Transmission in the Spread of HIV-1 Non-B Subtypes in Switzerland

von Wyl, Viktor ; Kouyos, Roger D. ; Yerly, Sabine ; Böni, Jürg ; Shah, Cyril ; Bürgisser, Philippe ; Klimkait, Thomas ; Weber, Rainer ; Hirschel, Bernard ; Cavassini, Matthias ; Staehelin, Cornelia ; Battegay, Manuel ; Vernazza, Pietro L. ; Bernasconi, Enos ; Ledergerber, Bruno ; Bonhoeffer, Sebastian ; Günthard, Huldrych F.

In: Journal of Infectious Diseases, 2011, vol. 204, no. 7, p. 1095-1103

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    Summary
    Background. By analyzing human immunodeficiency virus type 1 (HIV-1) pol sequences from the Swiss HIV Cohort Study (SHCS), we explored whether the prevalence of non-B subtypes reflects domestic transmission or migration patterns. Methods. Swiss non-B sequences and sequences collected abroad were pooled to construct maximum likelihood trees, which were analyzed for Swiss-specific subepidemics, (subtrees including ≥80% Swiss sequences, bootstrap >70%; macroscale analysis) or evidence for domestic transmission (sequence pairs with genetic distance <1.5%, bootstrap ≥98%; microscale analysis). Results. Of 8287 SHCS participants, 1732 (21%) were infected with non-B subtypes, of which A (n = 328), C (n = 272), CRF01_AE (n = 258), and CRF02_AG (n = 285) were studied further. The macroscale analysis revealed that 21% (A), 16% (C), 24% (CRF01_AE), and 28% (CRF02_AG) belonged to Swiss-specific subepidemics. The microscale analysis identified 26 possible transmission pairs: 3 (12%) including only homosexual Swiss men of white ethnicity; 3 (12%) including homosexual white men from Switzerland and partners from foreign countries; and 10 (38%) involving heterosexual white Swiss men and females of different nationality and predominantly nonwhite ethnicity. Conclusions. Of all non-B infections diagnosed in Switzerland, <25% could be prevented by domestic interventions. Awareness should be raised among immigrants and Swiss individuals with partners from high prevalence countries to contain the spread of non-B subtypes