Molecular epidemiology reveals long-term changes in HIV type 1 subtype B transmission in Switzerland.
BACKGROUND
Sequence data from resistance testing offer unique opportunities to characterize the structure of human immunodeficiency virus (HIV) infection epidemics.


METHODS
We analyzed a representative set of HIV type 1 (HIV-1) subtype B pol sequences from 5700 patients enrolled in the Swiss HIV Cohort Study. We pooled these sequences with the same number of sequences from foreign epidemics, inferred a phylogeny, and identified Swiss transmission clusters as clades having a minimal size of 10 and containing >or=80% Swiss sequences.


RESULTS
More than one-half of Swiss patients were included within 60 transmission clusters. Most transmission clusters were significantly dominated by specific transmission routes, which were used to identify the following patient groups: men having sex with men (MSM) (38 transmission clusters; average cluster size, 29 patients) or patients acquiring HIV through heterosexual contact (HETs) and injection drug users (IDUs) (12 transmission clusters; average cluster size, 144 patients). Interestingly, there were no transmission clusters dominated by sequences from HETs only. Although 44% of all HETs who were infected between 1983 and 1986 clustered with injection drug users, this percentage decreased to 18% for 2003-2006 (P<.001), indicating a diminishing role of injection drug users in transmission among HETs over time.


CONCLUSIONS
Our analysis suggests (1) the absence of a self-sustaining epidemic of HIV-1 subtype B in HETs in Switzerland and (2) a temporally decreasing clustering of HIV infections in HETs and IDUs.
Kouyos
Roger D
RD
Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich, Zurich, Switzerland. roger.kouyos@env.ethz.ch
von Wyl
Viktor
V
Yerly
Sabine
S
Böni
Jürg
J
Taffé
Patrick
P
Shah
Cyril
C
Bürgisser
Philippe
P
Klimkait
Thomas
T
Weber
Rainer
R
Hirschel
Bernard
B
Cavassini
Matthias
M
Furrer
Hansjakob
H
Battegay
Manuel
M
Vernazza
Pietro L
PL
Bernasconi
Enos
E
Rickenbach
Martin
M
Ledergerber
Bruno
B
Bonhoeffer
Sebastian
S
Günthard
Huldrych F
HF
D015658:HIV Infections / Q000453:epidemiology / Q000635:transmission* / Q000821:virology*; D015497:HIV-1 / Q000145:classification* / Q000235:genetics*; D020010:Heterosexuality; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D017720:Molecular Epidemiology; D010802:Phylogeny; D012307:Risk Factors; D015819:Substance Abuse, Intravenous; D013557:Switzerland / Q000453:epidemiology; D013997:Time Factors