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• 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: |
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HIV-1 the most common type found worldwide,
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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 (see Fact Sheets 4 & 5), 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 (See Fact Sheet 12). Blood transfusion or transfusion of blood products (eg. obtained from donor blood infected by HIV) (see Fact Sheet 12). Injecting equipment such as needles or syringes, or skin-piercing equipment, contaminated with HIV (see Fact Sheet 11). Mother to infant transmission of HIV/AIDS can occur during pregnancy, labour, and delivery or as a result of breast feeding (see Fact Sheet 10). |
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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"
(see Fact Sheet 12).
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 (see Fact Sheets 5 & 10 ). 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
(see Fact Sheet 5).
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 (see Fact Sheet 13) 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 (Fact Sheet 7)
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 (see Fact Sheet 12) · epidemiological surveillance of HIV prevalence (see Fact Sheet 2) · diagnosis of infection in individuals (see Fact Sheets 4 & 5) |
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 (see Fact Sheet 7). 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 (Fact Sheet 3), learning to prevent transmission to sexual partners (Fact Sheet 12) and planning for their own and their family's future (Fact Sheet 8).
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 (Fact Sheet
7) 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. (Issues related to pre and post-test counselling and
informed consent are covered in Fact Sheet 7.) 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) |