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Sexual Transmission of HIV
HIV can enter the bloodstream through mucous membranes, breaks,
sores and cuts in the mouth, anus, vagina or penis. Anal,
vaginal and oral intercourse (both receptive and penetrative)
can transmit HIV from person to person.
Unprotected anal intercourse is considered to be the
greatest sexual risk for transmitting HIV. Anal intercourse
frequently results in tears of mucous membranes, providing
a means of entry for the virus. The receptive partner ("bottom")
is considered to be at more risk of getting HIV, if the virus
is present. Risks may vary for the insertive ("top") partner.
Unprotected vaginal intercourse with the exchange
of semen, pre-ejaculate fluid, menstrual blood or vaginal
fluids is also a risk for HIV transmission. Women are more
likely to become infected with HIV through vaginal sex than
a man. The larger amount of mucous membrane surface area of
the vagina is a probable reason for women's greater rate of
HIV infection from their male partners.
Oral sex (mouth to penis, mouth to vagina, mouth to
rectum) is considered a risky behavior for HIV transmission
because of the exchange of semen, menstrual blood, and/or
vaginal fluids that may occur. Studies reported in February
2000 show that oral sex can definitively pass HIV from infected
partner to uninfected partner. The person who places their
mouth on the partner's genitals is at higher risk for HIV
infection than is the "receiving" partner. The actual risk
for HIV transmission to persons who are the receptive partner
in unprotected oral sex is unclear.
Injecting Drug Use and HIV Transmission
Sharing injection needles, syringes, and other injection
equipment with an HIV-infected person can put HIV directly
into the user's bloodstream and is the behavior which most
efficiently transmits HIV, as well as HBV and HCV.
Indirect sharing occurs when those who are injecting
drugs share injection paraphernalia and/or divide a shared
or jointly purchased drug while preparing and injecting it.
The paraphernalia that carries the potential for transmission
are the syringe, needle, "cooker" (often a spoon), cotton
(or other filter), and/or rinse water. Sharing these items
(sometimes called "works") may transmit HIV as well as other
viruses or bacteria.
Examples of indirect sharing:
- Squirting the drug back (from a dirty syringe) into the
drug cooker and/or someone else's syringe; and
- Sharing a common filter and/or rinse water.
Perinatal Transmission of HIV
An HIV-infected woman may transmit the virus to her baby
during pregnancy, during the birth process, and/or following
pregnancy by breastfeeding. Again, one of the predictors of
how infectious the woman will be to her baby is her viral
load (how much HIV is present in her bloodstream). Women with
new or recent infections, or people in later stages of AIDS
tend to have higher viral loads and may be more infectious.
Prior to the discovery, in 1994, that AZT (zidovudine) significantly
reduced the transmission of HIV from Mother to baby. Currently,
HIV is transmitted from an HIV-infected woman to her baby
in about 25% of pregnancies if intervention with antiretroviral
medications does not occur. Because of the widespread use
of AZT by HIV-infected pregnant women in the U.S., the perinatal
transmission rate has dropped dramatically, and is now less
than 2% in the U.S., especially if the woman's health care
is monitored closely and antiretroviral medications are used
during pregnancy and/or delivery. In some pregnancies, caesarian
section (C-section) may be recommended to reduce the risk
of transmission from woman to baby. Advice about medications
and C-section should be given on a case-by-case basis by a
healthcare provider with experience in treating HIV positive
pregnant women.
Breastfeeding is an established risk for HIV transmission.
One study in Africa showed that the rate of transmission of
HIV from infected mother to her child was 21% from breastfeeding.
Data from New York Department of Health studies show that
in the U.S., breastfeeding can add an additional 14% rate
of transmission of HIV from an infected woman to her child.
In the U.S., doctors recommend that a woman who knows she
is HIV-positive should not breastfeed her infant. Because
of the lack of clean water and the cost of infant formula
in developing countries, HIV-infected mothers in those areas
may not have a choice regarding breastfeeding.
Transfusions of Blood or Blood Products
Transmission by contaminated blood or blood products occurred
in the United States before March, 1985. In 1999, about 1%
of national AIDS cases were caused by transfusions or use
of contaminated blood products. The majority of those cases
were in people who received blood or blood products before
1985.
Donor screening, blood testing and other processing measures
have reduced the risk of transfusion-caused HIV transmission
to between 1 in 450,000 to 1 case in 600,000 transfusions
in the U.S. In the U.S., donating blood is always safe,
because sterile needles and equipment are used.
Transmission of Multi- Drug Resistant
Forms of HIV
There is evidence of transmission of multi-drug resistant
forms of HIV. People who have been infected with HIV and have
used a number of the available antiretroviral medicines may
transmit forms of HIV that are resistant to some of these
available drug therapies. This reduces the treatments available
for the newly-HIV-infected person. It is believed that inconsistent
use of antiretroviral medications can contribute to this multi-drug
resistant HIV. A discussion of treatments for HIV will occur
later in this course.
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Case Study
#3
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Ms. P. decided to have an HIV test after finding out
that an old boyfriend had HIV. She was shocked to hear
the news at first and went to the testing clinic knowing
there was a chance of infection, but she was confident
that she was in good health overall, and had not been
sick or had any unusual symptoms. She had dated this
boyfriend for about 3 months at least six years ago
but they just didn't "click." Eventually, they went
their own ways and began dating other people. Several
years ago she moved to a nearby city and changed jobs.
She only found out abut his illness by chance when she
happened to meet a mutual friend at an art festival.
When the test results came back positive she could
not believe it at first. Then, all at once, she began
to think about men she had been involved with since.
How many had she infected?
Ms. P. was given an appointment at an HIV treatment
center to discuss the need for antiretroviral therapy.
Before beginning therapy, the provider ordered a genotype
test to identify any possible viral resistance she might
have. When the results were back, she was informed that
she had been infected with a strain of virus that was
multi-drug resistant (MDR). In other words, many of
the commonly used medications for HIV would not provide
effective treatment. The provider also explained that
infection with HIV that is MDR is more common than many
people realize. In one recent study in NY City, 10%
of people newly diagnosed with HIV had MDR, and more
than 25% had at least some resistance (Shet et al.,
12th CROI, 2005). Medications would need to be carefully
selected to provide the best treatment possible. Even
so, infection with a strain of MDR HIV makes progression
to AIDS and death more likely.
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Factors Affecting HIV Transmission
There are a number of factors which affect HIV transmission.
These are:
- Presence of other STDs;
- Acute infection and/or high viral load;
- Multiple partners;
- Use of non-injecting drugs;
- Gender and equality issues.
The presence of other sexually transmitted diseases
(STDs) increases the risk for HIV transmission, because the
infected person may have a much larger number of white blood
cells, infected with HIV, present at the sore or infected
area(s).
The infected person's immune system may also be less able
to suppress or combat the HIV infection. Additionally, the
sores or lesions from STDs break down the protective surface
of the skin or mucous membrane, which makes the infected person
more vulnerable to other infections. More information on STDs
can be found later in this course.
Acute HIV infection (the first few weeks after infection
with HIV) is a time when a person may not know that s/he is
infected. However, the amount of virus (or viral load)
in her or his bloodstream can be extremely high. This may
make their blood, semen, vaginal fluids and/or breast milk
more infectious for HIV transmission. Antiretroviral therapy
can reduce a person's viral load, if the correct combination
is uses and the person adheres to the dosing schedule.
Having multiple partners for drug injection and/or sexual
intercourse increases the chances of being exposed to
a person infected with HIV. Persons who have unprotected sex
with multiple partners are considered to be at high risk for
HIV infection. In some studies, the CDC defines multiple partners
as six or more partners in a year. However, someone who has
one partner may still be at risk if the person is HIV-positive,
or if that one partner has sex with multiple other partners.
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Case Study
#4
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Ms. M. was married to her husband for 32 years before
he died from complications of coronary artery disease
several years ago. It was difficult for her to stop
grieving, and for the first year after his death seldom
did anything socially with anyone except family members.
Eventually she began attending functions at the senior
citizen center and met Paul. He was very kind, interesting,
funny, and they began dating. A year later, Paul became
sick and died.
The senior center hosted a program on life insurance
for seniors, and Ms. M. decided to apply for additional
coverage for her funeral expenses. Part of the criteria
was to have an HIV test, and she agreed to do so. She
did not think anything else about the insurance until
about one month later when she received a letter from
the company denying the coverage and suggesting that
she see her health care provider for a full examination.
She was frightened by the news, and called immediately
to make an appointment for the following week. She was
convinced she had cancer. Her provider was unable to
find anything abnormal on exam or lab tests. With her
permission he contacted the insurance company and was
faxed the positive results of her HIV test. She had
no idea how she was infected. Had her husband been infected
with HIV? Did Paul have HIV? Did either of them even
know they were infected? Did they know but did not tell
her?
Ms. M's provider made an appointment for counseling
to help her work through her grief and loss. He also
made an appointment with an HIV specialist for further
tests and care. He thoroughly evaluated the possibility
of self-harm before allowing her to leave his office.
Finally, he called a trusted friend with her permission
to drive her home.
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Use of other substances, including alcohol and non-injected
"street drugs," can also put a person at risk for getting
HIV. Impaired judgment may increase the likelihood that a
person will take risks (having unprotected sex, sharing needles)
or may place the person in unsafe situations. Additionally,
some substances have physiological and biological effects
on the body, including masking of pain and the creation of
sores on the mouth and genitals, which can create additional
"openings" for HIV and other sexually transmitted diseases.
Lack of power in a relationship can affect a person's
ability to insist on sexual protection, such as the use of
condoms. Women are often socially and economically dependent
upon men in many cultures. This can make them unable to "negotiate"
condom use or leave a relationship that puts them at risk.
In some cultures, females are not encouraged to learn about
their bodies, sex, birth control, or other sexuality topics.
Some cultures promote the value of the male having multiple
sexual partners, while discouraging the same behavior in females.
Continue on to Testing
for HIV/AIDS
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