How is HIV spread (transmitted)?
HIV is present to variable degrees in the blood and genital secretions of
virtually all individuals infected with HIV, regardless of whether or not they
have symptoms. The spread of HIV can occur when these secretions come in contact
with tissues such as those lining the vagina, anal area, mouth, eyes (the
mucus membranes), or with a break in the skin, such as from a cut or puncture by
a needle. The most common ways in which HIV is spreading throughout the world
include sexual contact, sharing needles, and by transmission from infected
mothers to their newborns during pregnancy, labor (the delivery process), or
breastfeeding. (See the section below on treatment during pregnancy for a
discussion on reducing the risk of transmission to the newborn.)
Sexual transmission of HIV has been described from men to men, men to women,
women to men, and women to women through vaginal, anal, and oral sex. The best
way to avoid sexual transmission is abstinence from sex
until it is certain that both partners in a monogamous relationship are not
HIV infected. Because the HIV antibody test can take months to turn positive after infection occurs, both partners would need to test negative for at least 12 and up to 24 weeks after their last potential exposure to HIV. If abstinence is out of the question, the next best method is the use of latex barriers. This involves placing a condom on the penis as soon as an erection is
achieved in order to avoid exposure to pre-ejaculatory and ejaculatory fluids
that contain infectious HIV. For oral sex, condoms should be used for fellatio
(oral contact with the penis) and latex barriers (dental dams) for cunnilingus
(oral contact with the vaginal area). A dental dam is any piece of latex that
prevents vaginal secretions from coming in direct contact with the mouth.
Although such dams occasionally can be purchased, they are most often created by
cutting a square piece of latex from a condom.
The spread of HIV by exposure to infected blood usually
results from sharing needles, as in those used for illicit drugs. HIV also can
be spread by sharing needles for anabolic steroids to increase muscle,
tattooing, and body piercing. To prevent the spread of HIV, as well as other
diseases including hepatitis, needles should never be shared. At the beginning
of the HIV epidemic, many individuals acquired HIV infection from blood
transfusions or blood products, such as those used for hemophiliacs. Currently, however, because blood is tested for both antibodies to HIV and the actual virus before transfusion, the risk of acquiring HIV from a blood transfusion in the United States is extremely small and is considered insignificant.
There is little evidence that HIV can be transferred by casual exposure, as
might occur in a household setting. For example, unless there are open sores or
blood in the mouth, kissing is generally considered not to be a risk factor for
transmitting HIV. This is because saliva, in contrast to genital secretions, has
been shown to contain very little HIV. Still, theoretical risks are associated
with the sharing of toothbrushes and shaving razors because they can cause
bleeding, and blood can contain large amounts of HIV. Consequently, these items
should not be shared with infected people. Similarly, without sexual exposure
or direct contact with blood, there is little if any risk of HIV contagion in
the workplace or classroom.