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How is HIV transmitted?
A
person who is HIV-infected carries the virus in certain body fluids,
including blood, semen, vaginal secretions, and breast milk. The virus
can be transmitted only if such HIV-infected fluids enter the
bloodstream of another person. This kind of direct entry can occur (1)
through the linings of the vagina, rectum, mouth, and the opening at the
tip of the penis; (2) through intravenous injection with a syringe; or
(3) through a break in the skin, such as a cut or sore. Usually, HIV is
transmitted through:
Unprotected sexual intercourse (either vaginal or anal) with someone who
is HIV infected.
Women are at greater risk of HIV infection through vaginal sex than men,
although the virus can also be transmitted from women to men. Anal sex
(whether male-male or male-female) poses a high risk mainly to the
receptive partner, because the lining of the anus and rectum are
extremely thin and filled with small blood vessels that can be easily
injured during intercourse.
Unprotected oral sex with someone who is HIV infected.
There are far fewer cases of HIV transmission attributed to oral sex
than to either vaginal or anal intercourse, but oral-genital contact
poses a clear risk of HIV-infection, particularly when ejaculation
occurs in the mouth. This risk is increased when either partner has cuts
or sores, such as those caused by sexually transmitted diseases (STDs),
recent tooth-brushing, or canker sores, which can allow the virus to
enter the bloodstream.
Sharing needles or syringes with someone who is HIV infected.
Laboratory studies show that infectious HIV can survive in used needles
for a month or more. That is why people who inject drugs should never
reuse or share syringes, water, or drug preparation equipment. This
includes needles or syringes used to inject illegal drugs such as
heroin, as well as steroids. Other types of needles, such as those used
for body piercing and tattoos, can also carry HIV.
Infection during pregnancy, childbirth, or breast-feeding
(mother-to-infant transmission).
Any
woman who is pregnant or considering becoming pregnant and thinks she
may have been exposed to HIV even if the exposure occurred years ago
should seek testing and counselling. Those who test positive are
provided with drugs to prevent transmission and counselled not to
breast-feed.
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