Amount of HIV in Genital Fluid Linked to
WEDNESDAY, April 6 (HealthDay News) -- In a development that
could enhance HIV-prevention research, a new study of heterosexual
couples confirms that the risk of transmitting HIV rises with the
level of the virus in semen and cervical fluid.
The finding -- that more virus translates to higher likelihood
of transmission -- hasn't been proven to this extent before, said
study lead author Dr. Jared M. Baeten of the University of
Washington in Seattle.
"This confirms what we had thought about the biology of HIV," he said, "and it gives us new information about genital levels of HIV being particularly important, even independent of blood levels."
For the study, researchers obtained samples of genital fluid
from 2,521 heterosexual couples living in seven African countries.
Most were married and living together. At the start of the two-year
study, one partner in each couple was infected with HIV, the
AIDS-causing virus, and none was taking anti-HIV drugs.
Over the course of the study, published April 6 in the journal
Science Translational Medicine, 78 partners became infected within the relationship.
The researchers compared cervical and semen fluid samples from
partners who transmitted the virus with samples from men and women
who didn't transmit the virus and found that the risk of HIV
transmission approximately doubled with each specified HIV increase
in genital fluids. (In a few cases, HIV transmission occurred
without any sign of the virus in genital fluids, although it was in
The results are "really useful for figuring out new research
studies looking at new strategies," said Baeten, an assistant
professor of global health and medicine. "You can develop
strategies that reduce HIV levels only in the genital tract, not in
the blood, like microbicides."
The study is useful for a couple of reasons, said Dr. Peter A.
Anton, director of the Center for HIV Prevention Research at
University of California Los Angeles, who co-wrote a commentary
accompanying the study. Not only does it suggest a way of
determining who is most likely to infect a partner, it also enables
researchers to study those who
didn't infect the people they had sex with.
This can help researchers better understand "the natural
protections that the penis, the vagina and the rectum have that we
want to make sure we preserve," he said. The study "is highlighting
what we need to look at going forward," he added.
Still, the study, which Anton said was "really well done," has
some limitations. It only looked at heterosexual couples and not at
people at higher risk of becoming infected with HIV, such as
sex-trade workers and gay men.
And the study doesn't examine how often HIV-positive people with
no detectable virus in their blood transmit the disease to their
partners. Anti-HIV drugs can often reduce the level of HIV in blood
to zero, while the virus hides in other parts of the body.
Worldwide, more than 7,000 new HIV infections are diagnosed
daily, according to background information in Anton's commentary.
In the big picture, these new findings can only do so much to curb
the rate of HIV infection, he said.
Noting that many HIV-positive people are unaware they have the
disease, Anton said, "The biggest issue in transmission is that
many people don't know their status."
For more about
HIV/AIDS, visit the U.S. National Library of Medicine.
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