Serosorting
-- a practice in which people have unprotected intercourse only with others of
the same HIV serostatus -- has been proposed by some harm reduction advocates
as a way to reduce the risk of HIV
transmission.
But
the benefits of serosorting are only as good as the accuracy of a partner's serostatus
disclosure, and a new mathematical model suggests that it may actually increase
the risk of transmission in some circumstances, since recently infected individuals
may still believe they are HIV negative.
"The effectiveness of a serosorting
strategy for HIV prevention depends on the accuracy of individuals' serostatus
disclosures," researchers from the University of California at San Diego
wrote in the May 31, 2007 issue of AIDS. "We modeled the risks of
sexual transmission of HIV under various circumstances differing by the type of
disclosures made. Accounting for rates of unrecognized HIV infection, treatment
status, and differences in infectivity by stage of infection, we found that serosorting
can increase the transmission risk for some groups."
Not only are viral loads high during the earliest stages
of infection, but most people are not aware they are infected. They may have become
infected since their last test, or may have been tested during the "window
period" before the body has had a chance to produce enough antibodies to
be detected by the test. Thus, such individuals may inadvertently inform a potential
sex partner that they are HIV negative when this is no longer the case.
According
to the mathematical model, the benefits of serosorting decrease as the proportion
of recently infected individuals in a population of potential sex partners increases.
Indeed, an HIV negative person may actually be at less risk from having sex with
a known HIV positive partner with chronic infection (especially if they are receiving
effective antiretroviral therapy) than with a supposedly HIV negative partner
who actually has acute infection.
"The effectiveness of serosorting
on the basis of mutual disclosure of perceived HIV status is a flawed strategy
for reducing sexual transmissions of HIV when it does not consider the prevalence
of recent HIV infections in specific populations," the authors wrote. "
By ignoring the increased potential for HIV transmission by recently infected
individuals, serosorting may paradoxically increase the number of new HIV infections
in certain populations."
06/15/07
Reference DM
Butler and DM Smith. Serosorting can potentially increase HIV transmissions. AIDS
21(9): 1218-1220. May 31, 2007.
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