The
risk of HIV transmission through condom-less anal intercourse is seen
to be extremely high, as much 18 times greater than vaginal intercourse
according a meta-analysis conducted by researchers at Imperial College
and the London School of Hygiene and Tropical Medicine in 2010. The
reasons for the increased risk are well known and include such factors
as:
-
The fragility of rectal tissues, allowing the virus a direct access into the bloodstream through tiny tears or abrasions.
-
The porousness of rectal tissues and their high susceptibility to infection even when undamaged.
-
The
high concentration of HIV in semen and pre-seminal fluid (“pre cum”),
which can double the risk of infection with every one-log (i.e., one
digit) rise in the person’s viral load.
Furthermore,
the secretion of blood from damaged rectal tissues can increase the
risk for the insertive (“top”) partner, providing the virus a route of
transmission through the urethra and/or Langerhans cells that line the
head of the penis (particularly under the foreskin).
AIDS/HIV Expert