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Introduction: What is HIV/AIDS?
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HIV transmission
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Natural history of HIV infection
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Acute HIV
infection
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HIV
infection before the onset of symptoms
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Progression
of HIV
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Testing for HIV antibodies
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Informed consent and confidentiality
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Questions for reflection and discussion
• Introduction: What is HIV/AIDS?
In 1983 the virus that caused AIDS was discovered by scientists in France and the routes of transmission were confirmed. The virus eventually became known as the human immunodeficiency virus (HIV). There are 2 different types of HIV:
HIV-1
the most common type found worldwide, and
HIV-2 found mostly in West Africa.
HIV infection affects
the immune system. The immune system is the body's defense against
infections by microorganisms (such as very small bacteria or viruses)
that get past the skin and mucous membranes and cause disease. The
immune system produces special cells called antibodies to fight off or
kill these microorganisms. A special weakness of the immune system is
called an immunodeficiency. Human immunodeficiency virus (HIV) infects,
and eventually destroys, special cells in the immune system called
lymphocytes and monocytes.
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| Nurses and midwives in Ghana participate in HIV/AIDS Awareness Days by developing key messages for the public. (Credit: JHU/CCP) |
These cells carry
the CD4 antigen on their surface (CD4+ lymphocytes). HIV recognizes the
CD4 antigen and enters and infects CD4+ lymphocytes. The result is the
killing of many CD4+ lymphocytes. This slowly leads to a persistent,
progressive and profound impairment of the immune system, making an
individual susceptible to infections and conditions such as cancer. HIV
is the beginning stage of infection and can be detected by a blood test
(described in this Fact Sheet). When the immune system becomes very
affected, the illness progresses to AIDS. Blood tests (described in this
Fact Sheet), or the appearance of certain infections, indicate that the infection has progressed to AIDS.
• HIV transmission
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HIV
can be transmitted by:
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Sexual intercourse (vaginal, anal and oral) or through contact with infected blood, semen, or cervical and vaginal fluids. This is the most frequent mode of transmission of HIV world wide, and can be transmitted from any infected person to his or her sexual partner (man to woman, woman to man, man to man and, but less likely, woman to woman). The presence of other sexually transmitted diseases (STDs) (especially those causing genital ulcers) increase the risk of HIV transmission because more mucous membrane is exposed to the virus. Blood transfusion or transfusion of blood products (eg. obtained from donor blood infected by HIV). Injecting equipment such as needles or syringes, or skin-piercing equipment, contaminated with HIV. Mother to infant transmission of HIV/AIDS can occur during pregnancy, labour, and delivery or as a result of breast feeding. |
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HIV
can NOT be transmitted by:
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| Coughing
or sneezing Insect bites Touching or hugging Water or food Kissing Public baths |
Handshakes Work or school contact Using telephones Swimming pools Sharing cups, glasses, plates, and other utensils |
• Natural history of HIV infection
Acute HIV
infection
Most people infected
with HIV do not know that they have become infected. HIV infected
persons develop antibodies to HIV antigens usually 6 weeks to 3 months
after being infected. In some individuals, the test for the presence of
these antigens may not be positive until 6 months or longer (although
this would be considered unusual). This time -- during which people can
be highly infectious and yet unaware of their condition -- is known as
the "the window period".
Seroconversion is when a person recently infected with HIV first tests sero-positive for HIV antibodies. Some people have a "glandular fever" like illness (fever, rash, joint pains and enlarged lymph nodes) at the time of seroconversion. Occasionally acute infections of the nervous system (eg. aseptic meningitis, peripheral neuropathies, encephalitis and myelitis) may occur.
HIV
infection before the onset of symptoms
In adults, there is
often a long, silent period of HIV infection before the disease
progresses to "full blown" AIDS. A person infected with HIV
may have no symptoms for up to 10 years or more. The vast majority of
HIV-infected children are infected in the peri-natal period, that is,
during pregnancy and childbirth. The period without symptoms is shorter
in children, with only a few infants becoming ill in the first few weeks
of life. Most children start to become ill before 2 years; however, a
few remain well for several years.
Progression
from HIV infection to HIV-related disease and AIDS
Almost all (if not
all) HIV-infected people will ultimately develop HIV-related disease and
AIDS. This progression depends on the type and strain of the virus and
certain host characteristics. Factors that may cause faster progression
include age less than 5 years, or over 40 years, other infections, and
possibly genetic (hereditary) factors. HIV infects both the central and
the peripheral nervous system early in the course of infection. This
causes a variety of neurological and neuropsychiatric conditions. As HIV
infection progresses and immunity declines, people become more
susceptible to opportunistic infections.
These
include:
| Tuberculosis Other sexually transmitted diseases Septicaemia Pneumonia (usually pneumocystis carinii) Recurrent fungal infections of the skin, mouth and throat Unexplained fever Meningitis |
| Other Conditions: |
| Other
skin diseases Chronic diarrhoea with weight loss (often known as "slim disease") Other diseases such as cancers (eg. Kaposi sarcoma) |
Any blood test
used to detect HIV infection must have a high degree of sensitivity (the
probability that the test will be positive if the patient is infected)
and specificity (the probability that the test will be negative if the
patient is uninfected). Unfortunately, no antibody test is ever 100 %
sensitive and specific. Therefore, if available, all positive test
results should be confirmed by retesting, preferably by a different test
method. HIV antibody tests usually become positive within 3 months of
the individual being infected with the virus (the window period). In
some individuals, the test may not be positive until 6 months or longer
(considered unusual). In some countries, home testing kits are
available. These tests are not very reliable, and support such as pre
and post test counselling is not available.
• Testing for HIV antibodies
Tests for HIV
detect the presence of antibodies to HIV, not the virus itself. Although
these tests are very sensitive, there is a "window period. "
This is the period between the onset of infection with HIV and the
appearance of detectable antibodies to the virus. In the case of the
most sensitive anti-HIV tests currently recommended, the window period
is about three weeks. This period may be longer if less sensitive tests
are used.
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The
three main objectives for which HIV antibody testing is
performed are:
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screening of donated blood · epidemiological surveillance of HIV prevalence · diagnosis of infection in individuals |
Screening of donated blood accounts for the majority of HIV tests performed worldwide. It is a highly cost effective preventive intervention as the transmission of HIV through infected blood is at least 95%.
At the beginning of the HIV epidemic, HIV testing was used mostly for clinical confirmation of suspected HIV disease. More recently, people have been encouraged to attend voluntary counselling and testing (VCT) services to find out their HIV status. It is hoped that if people know their HIV status and are seronegative, they will adopt preventive measures to prevent future infection (see Fact Sheet 12). If the person is seropositive, it is hoped that they will learn to live positively, accessing care and support at an earlier stage, learning to prevent transmission to sexual partners and planning for their own and their family's future.
Antibody
tests
Traditionally, HIV testing has been done using ELISA
(Enzyme Linked ImmunoSorbent Assay). However, there are various
essential requirements for ELISAs to be performed accurately:
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Laboratory equipment (eg. pipettes, microtiter trays,
incubators, washers, and ELISA readers) must be available · Constant supply of electricity, and regular maintenance of equipment · Skilled technicians · Accurate storage and testing temperatures |
Recent advances in
technology have lead to various simple rapid tests being developed.
Most of these tests come in a kit and require no reagent, equipment,
training, or specified temperature controls, and tests can be
performed at any time. These tests are as accurate as ELISA and
results can be obtained within hours. In some countries, over 50% of
people do not return for their test results. With these rapid tests,
people can wait for their results. Although the costs of these simple
rapid tests are higher than ELISA they will be useful in STD clinics,
antenatal clinics, and counselling centres, because of the ease of
use. In some countries, home testing kits are also available. These
tests are not very reliable, and support such as pre and post test
counselling is not available.
False
positive result
HIV tests have been developed to be especially
sensitive and, consequently, a positive result will sometimes be
obtained even when there are no HIV antibodies in the blood. This is
known as a false positive, and because of this, all positive results
must be confirmed by another test method. A confirmed positive result
from the second test method means that the individual is infected with
HIV.
False
negative result
A false negative result occurs when the blood tested
gives a negative result for HIV antibodies when in fact the person is
infected, and the result should have been positive. The likelihood of
a false negative test result must be discussed with patients if their
history suggests that they have engaged in behaviour which was likely
to put them at risk of HIV infection. In this situation, repeated
testing over time may be necessary before they can be reassured that
they are not infected with HIV. The most frequent reason for a false
negative test result is that the individual is newly infected (ie. the
window period) and is not yet producing HIV antibodies. However, it is
important to remember that someone who has tested negative because
they are not infected with HIV can become infected the following day!
• Informed consent and confidentiality
All people
taking an HIV test must give informed consent prior to being tested.
The results of the test must be kept absolutely confidential. However,
shared confidentiality is encouraged. Shared confidentiality refers to
confidentiality that is shared with others. These others might include
family members, loved ones, care givers, and trusted friends. This
shared confidentiality is at the discretion of the person who will be
tested. Although the result of the HIV test should be kept
confidential, other professionals such as counsellors and health and
social service workers, might also need to be aware of the person's
HIV status in order to provide appropriate care.
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Questions
for Reflection and Discussion
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| Why
is it important that nurses/midwives educate people about how
HIV is and is not transmitted? What role can nurses/midwives take in promoting HIV prevention? Why is it important to understand the danger of HIV transmission during the "window period"? Why is informed consent essential? What role can nurses/midwives play in promoting shared confidentiality? What are the dangers of receiving a false negative result? What should be done if a person's test is sero-negative? |
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References
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| World
Health Organization (1993). HIV Prevention and Care: Teaching
Modules for Nurses and Midwives. WHO/GPA/CNP/TMD/93.3 World Health Organization (1996). TB/HIV: A Clinical Manual. (WHO/TB/96.200) World Health Organization (1997). Standard treatments and essential drugs for HIV-related conditions. Access to HIV-related drugs (DAP/97.9) |