Circumcising
men reduced infections in their female partners by 30 percent, the
researchers found. One said the difference may be related to the
structure of the foreskin, which is removed in
circumcision.
In
the study of more than 300 Ugandan couples in which the man
infected the woman, the researchers found that 299 women caught
HIV from uncircumcised partners and only 44 were infected by
circumcised men.
Circumcision
also reduced the risk of infection with other sexually-transmitted
diseases such as trichomonas and bacterial vaginosis, but not
syphilis, gonorrhea or chlamydia, the researchers told an AIDS
meeting in Denver.
Dr.
Thomas Quinn of Johns Hopkins University in Baltimore has been
leading a team that studies 12,000 volunteers in Rakai, Uganda.
They have been studying transmission of the human immunodeficiency
virus that causes AIDS.
Last
year they reported that circumcised men were less likely to become
infected with HIV. Now, they told the Conference on Retroviruses
and Opportunistic Infections, it appears that among infected men,
circumcision reduces the likelihood they will transmit the virus
through sex.
They
also presented more evidence that circumcision protects men. They
reanalyzed previous studies and found that circumcision reduced
the risk of HIV infection in men by 50 percent -- and by 70
percent in the highest-risk men.
The
findings will have to be confirmed in other groups before being
used as the basis for recommendations, Quinn said. However, he
said, “early indications are dramatic.” If borne out, for every 15
to 60 circumcisions, one case of HIV infection could be prevented,
he said.
Circumcision’s
benefits may stem from the structure of the foreskin of the penis.
Its inner lining, or mucosa, carries cells that are vulnerable to
the AIDS virus.
“Also
that mucosal layer does not have the thick keratin (skin) that the
outside skin of the foreskin has,” Oliver Laeyendecker, who worked
on the study, said in an interview.
“Not
only do you have more virus there because of the types of cells
that are there, but the barrier is easier to go through from the
man to the woman on that skin surface because it doesn’t have to
go through a lot.”
The
AIDS virus is transmitted by semen, blood and breast milk and via
sex, shared needles or other contacts with infected
blood.
Semen
can transmit the virus, but levels in the semen drop over time,
while remaining elevated in the blood, Laeyendecker
said.
The
theory is that the virus can pass in tiny amounts of blood in the
foreskin. “Because of the nature of that membrane, because it is
thin, because it is susceptible to micro-tears, you have a lot of
openings,” Laeyendecker said.
“Plus
you have more cells with virus there, so it lends itself to being
a more transmissible surface.”
The
AIDS virus infects close to 40 million people globally, most of
them in Africa. It kills 3 million people a year and infects 5
million new people every year.
It
is eventually fatal and there is no cure or vaccine, although drug
cocktails can keep patients healthy for years. Laeyendecker said
the Uganda volunteers have access to at least some of the drugs
through a US program.
