Rates of HIV-1 transmission per coital act, by stage of HIV-1 infection, in Rakai, Uganda.
BACKGROUND
We estimated rates of human immunodeficiency virus (HIV)-1 transmission per coital act in HIV-discordant couples by stage of infection in the index partner.


METHODS
We retrospectively identified 235 monogamous, HIV-discordant couples in a Ugandan population-based cohort. HIV transmission within pairs was confirmed by sequence analysis. Rates of transmission per coital act were estimated by the index partner's stage of infection (recent seroconversion or prevalent or late-stage infection). The adjusted rate ratio of transmission per coital act was estimated by multivariate Poisson regression.


RESULTS
The average rate of HIV transmission was 0.0082/coital act (95% confidence interval [CI], 0.0039-0.0150) within approximately 2.5 months after seroconversion of the index partner; 0.0015/coital act within 6-15 months after seroconversion of the index partner (95% CI, 0.0002-0.0055); 0.0007/coital act (95% CI, 0.0005-0.0010) among HIV-prevalent index partners; and 0.0028/coital act (95% CI, 0.0015-0.0041) 6-25 months before the death of the index partner. In adjusted models, early- and late-stage infection, higher HIV load, genital ulcer disease, and younger age of the index partner were significantly associated with higher rates of transmission.


CONCLUSIONS
The rate of HIV transmission per coital act was highest during early-stage infection. This has implications for HIV prevention and for projecting the effects of antiretroviral treatment on HIV transmission.
Wawer
Maria J
MJ
Heilbrun Department of Population and Family Health, Columbia University Mailman School of Public Health, New York, New York 10032, USA. mwawer@jhsph.edu
Gray
Ronald H
RH
Sewankambo
Nelson K
NK
Serwadda
David
D
Li
Xianbin
X
Laeyendecker
Oliver
O
Kiwanuka
Noah
N
Kigozi
Godfrey
G
Kiddugavu
Mohammed
M
Lutalo
Thomas
T
Nalugoda
Fred
F
Wabwire-Mangen
Fred
F
Meehan
Mary P
MP
Quinn
Thomas C
TC
D000163:Acquired Immunodeficiency Syndrome / Q000453:epidemiology* / Q000473:pathology / Q000635:transmission*; D000293:Adolescent; D000328:Adult; D003075:Coitus; D005260:Female; D015497:HIV-1 / Q000302:isolation & purification*; D006801:Humans; D015994:Incidence; D008297:Male; D016012:Poisson Distribution; D012749:Sexually Transmitted Diseases / Q000635:transmission* / Q000821:virology; D013997:Time Factors; D014454:Uganda / Q000453:epidemiology; D019562:Viral Load