HIV-1 subtypes were determined in newly diagnosed residents of Switzerland.
Blood was anonymously collected from patients with a first confirmed posit
ive HIV-1 test result. Viral DNA from the env V3-V5 region was amplified by
nested polymerase chain reaction (PCR) and screened for subtype B by heter
oduplex mobility assay. All amplicons not identified as B were sequenced. F
rom November 1996 to February 1998, 206 samples were analyzed. Main transmi
ssion risks were unprotected heterosexual (55.7%) or homosexual (27.1%) sex
ual contact or intravenous drug use (12.9%). Subtype B dominated in patient
s of Swiss, other European, American, or Asian citizenship; particularly hi
gh frequencies were found in homosexuals (97%) and drug users (94%). Non-B
subtypes including A, C, D, E, F, G, H, a possible B/F recombinant, and a s
equence related to J were present in 28.2% (95% confidence interval [CI], 2
2.9%-35.0%). Non-B were frequent in African citizens (95%), heterosexually
infected individuals (44%), and women (43%). Heterosexually infected Swiss
males harbored non-B strains in 18% and females in 33%. The results documen
t a change in the epidemiology of newly diagnosed HIV-1 infections in Switz
erland: predominance of heterosexual transmission and a high frequency of n
on-B subtypes.