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Risk
for Female-to-Male Sexual HIV Transmission May Be Greater Than 2-fold
Higher for Uncircumcised Than for Circumcised Men
A
lack of male circumcision has been associated with increased risk
of HIV-1 acquisition in a number of studies, but questions remain
as to whether confounding by behavioral practices explains these
results. The objective of the present study was to model per sex
act probabilities of female-to-male HIV-1
transmission (i.e., infectivity) for circumcised and
uncircumcised men, by use of detailed accounts of sexual behavior
in a population with multiple partnerships.
Data
were collected as part of a prospective cohort study of HIV-1 acquisition
among 745 Kenyan truck drivers. Sexual behavior with wives, casual
partners, and prostitutes was recorded at quarterly follow-up visits.
Published HIV-1 seroprevalence estimates
among Kenyan women were used to model HIV-1 persex
act transmission probabilities.
Results
The
overall probability of HIV-1 acquisition per sex act was 0.0063
(95% confidence interval, 0.00350.0091). Female-to-male
infectivity was significantly higher for uncircumcised men than
for circumcised men (0.0128 vs. 0.0051; P = .04). The effect of
circumcision was robust in subgroup analyses and across a wide range
of HIV-1 prevalence estimates for sex partners.
Conclusions
After
accounting for sexual behavior, the authors found that uncircumcised
men were at a >2-fold increased risk of acquiring HIV-1 per sex
act, compared with circumcised men. Moreover, female-to-male infectivity
of HIV-1 in the context of multiple partnerships may be considerably
higher than that estimated from studies of HIV-1serodiscordant
couples. These results may explain the rapid spread of the HIV-1
epidemic in settings, found throughout much of Africa, in which
multiple partnerships and a lack of male circumcision are common.
Discussion
These
results suggest that the probability of female-to-male
sexual HIV-1 transmission might be >2-fold higher
for uncircumcised men than for circumcised men.
Moreover, HIV-1 infectivity in an African
population with multiple partnerships may
be substantially greater than previously estimated
from studies of monogamous HIV-1serodiscordant
couples.
The
authors conclude, The high probability of per-contact
HIV-1 transmission seen in our study may explain
the rapid spread of the HIV-1 epidemic in
settings where multiple, concurrent partnerships
are common. Moreover, our results strengthen the
substantial body of evidence suggesting that variation
in the prevalence of male circumcision may
be a principal contributor to the spread of
HIV-1 in Africa.
Departments
of Epidemiology, Biostatistics, and Medicine, University of Washington,
and Division of Public Health Sciences, Fred Hutchinson Cancer Research
Center, Seattle; Department of Medical Microbiology, University
of Nairobi, Nairobi, and Coast Provincial General Hospital, Mombasa,
Kenya.
01/21/05
Reference
J M Baeten
and others. Female-to-Male Infectivity of HIV-1 among Circumcised
and Uncircumcised Kenyan Men. The Journal of Infectious Diseases 191(4):
546-553. February 15, 2005.
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