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Human
immunodeficiency virus infection: An Infection caused by one of
two related retroviruses (HIV-1 and HIV-2) resulting in a wide
range of clinical manifestations varying from asymptomatic
carrier states to severely debilitating and fatal disorders
related to defective cell-mediated immunity.
HTLV-I and HTLV-II
are both lymphotropic and oncogenic, type C retroviruses,
causing adult T-cell leukemia/lymphomas in < 5% of infected
persons. Expansion of CD4+ T (helper) lymphocytes in the tissues
and circulation leads to leukemia, diffuse lymphadenopathy,
hepatosplenomegaly, and skin lesions.
Many patients
appear to be immunosuppressed and some are subject to the same
opportunistic infections as those with advanced HIV infections.
HTLV-I is also neurotropic, causing a progressive myelopathy
(tropical spastic paraparesis or HTLV-associated myelopathy
[HAM]) in < 1% of carriers. A few cases of myelopathy have
been described in HTLV-II carriers. Clinically, HAM is a
progressive spastic paraparesis with weakness, stiffness,
numbness, dysesthesias of the legs, and urinary frequency and
incontinence presenting within the first decade after infection.
HTLV-I is
transmitted sexually and through blood, but most infections
appear to be transmitted vertically from mother to child by
breastfeeding. The patterns of disease and seroprevalence for
HTLV-I suggest that it is widely, but not homogeneously,
distributed. For example, high levels of HTLV-I are present in
southern Japan and the Caribbean and among IV drug users and
prostitutes in some U.S. cities. The human retrovirus that has
had the greatest social and medical impact is HIV-1, which was
identified in 1984 as the cause of a widespread epidemic of
severe immunosuppression called acquired immunodeficiency
syndrome (AIDS). AIDS is a disorder of cell-mediated immunity
characterized by opportunistic infections, malignancies,
neurologic dysfunction, and a variety of other syndromes. AIDS
is the most severe manifestation of a spectrum of HIV-related
conditions
Transmission
HIV transmission
requires contact with body fluids containing infected cells or
plasma. HIV may be present in any fluid or exudate that contains
plasma or lymphocytes, specifically blood, semen, vaginal
secretions, breast milk, saliva, or wound exudates. Although
theoretically possible, transmission by saliva or droplet nuclei
produced by coughing or sneezing is extremely rare, if it
occurs. HIV is not transmitted by casual contact or even by the
close nonsexual contact that occurs at work, school, or
home.
The most common
means of transmission is direct transfer of bodily fluids either
through sharing contaminated needles or sexual relations.
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Sexual
practices involving no exposure to bodily fluids are safe.
Other practices, such as fellatio and cunnilingus appear to
be relatively, but not absolutely, safe. The greatest risk
is through genital intercourse, especially anal-receptive
intercourse. Sexual practices producing mucosal trauma
before or during intercourse increase the risk. Use of
latex, but not natural membrane, condoms or vaginal barriers
decreases but does not eliminate risk. Oil-based lubricants
decrease the protection provided by latex condoms because
they dissolve them. Infected cells or free virions can reach
target cells in a new host via blood transfusion, accidental
injection, or mucous membrane exposure. The role of mucous
membrane inflammation is illustrated by the effect of other
sexually transmitted diseases (STDs) on susceptibility to
HIV infection. HIV transmission is definitely increased by
chancroid and may be more likely in the presence of herpes,
syphilis, trichomoniasis, and possibly other STDs.
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Transmission
of HIV by needle-stick injury, estimated at about 1/300
incidents, is much less frequent than transmission of
hepatitis B, presumably because of the relatively lower
number of HIV virions in the blood of most infected
patients. Risk of HIV transmission appears to be increased
by deep wounds or injection of blood, such as when
hollow-bore needles containing blood penetrate the skin.
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Risk of HIV
transmission from infected medical personnel who observe
good techniques to uninfected patients is very small but is
less clear. Transmission from a single dentist to at least
six of his patients has been documented. However, extensive
investigations of patients cared for by other HIV-infected
physicians and surgeons have failed to uncover other cases.
The means of transmission of HIV from the dentist to his
patients is not understood and remains a troubling, but
apparently unique, episode. Procedures or situations from
which HIV-infected medical personnel should be excluded have
not been clearly identified. Transmission of HIV during
medical care is a potential problem if transfused blood is
not screened or medical instruments are not adequately
sterilized.
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Use of
enzyme-linked immunosorbent assay (ELISA) to screen blood
donors has vastly reduced the risk of acquiring HIV by
transfusion. However, persons in the early stages of HIV
infection, who have not yet mounted an antibody response,
may have transiently negative ELISA and Western blot results
while yielding positive results for HIV p24 antigen in
plasma. These persons may account for the very low, but
continuing, risk of transfusion-associated HIV infection
(estimated at between 1/10,000 and 1/100,000 per unit
transfused). Currently mandated screening for both antibody
and p24 antigen may further reduce this risk.
Epidemiology
Since AIDS was
first recognized in 1981 when cases of Pneumocystis carinii
pneumonia and Kaposi's sarcoma were reported in homosexual men
in California and New York, > 581,000 cases and 357,000
deaths have been reported through December 1996 in the USA. Over
30 million HIV infections and 10 million AIDS cases are
estimated worldwide.
Two epidemiologic
patterns of HIV transmission are recognized:
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Type
1: In the USA and
Europe, transmission is primarily homosexual or via blood.
Most patients are 20- to 49-yr-old men in high-risk groups (eg,
homosexual or bisexual men, IV drug users who share needles,
and recipients of transfused blood or blood components who
sometimes transmit HIV to women heterosexually). In the USA,
women are an increasing proportion (about 20%) of all AIDS
cases. Among persons with hemophilia and other bleeding
disorders, AIDS has become the leading cause of death.
Before 1985, the risk of HIV infection among hemophiliacs
correlated with large requirements for factor VIII
concentrates and the origin of their plasma products in the
USA. The wide distribution of commercial plasma products
originating in the USA resulted in a high rate of HIV
infection, even in recipients from areas not initially
affected by the epidemic. In most of Europe, where clotting
factor material was collected from populations with lower
risk of HIV infection, fewer hemophiliacs were infected.
However, routine use of screened and heat-treated blood or
bioengineered treatments for hemophilia has subsequently
eliminated the risk of infection.
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Type
2: In Africa, South
America, and Southern Asia, transmission is primarily
heterosexual. In these areas, men and women are nearly
equally affected. Mixtures of the two patterns have been
found in countries such as Brazil and Thailand. Typically,
diseases follow routes of transportation and trade to cities
and secondarily to rural areas. The continuing spread of HIV
in developing countries with minimal resources with which to
manage the epidemic has grave implications. The spread of
two distinct serogroups of HIV-1 in Thailand is
illustrative. In about 1990, parallel epidemics of
heterosexually transmitted (genotype A) and
needle-transmitted (genotype B) HIV rapidly infected female
prostitutes and their clients and IV opiate users who shared
needles.
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Infection of
large numbers of women of childbearing age has led to a
substantial number of pediatric cases of AIDS (Human
Immunodeficiency Virus Infection in Children) - HIV can be
transmitted transplacentally or perinatally. The virus has
been found in breast milk, and breastfeeding has been
implicated in transmission. In addition, groups of newborns
and children have become infected from repeated use of
inadequately sterilized needles.
Symptoms
and Signs
HIV causes a
broad spectrum of clinical problems, which may mimic other
diseases.
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Immediately
after infection and for a prolonged period (more than
several months in a small number of persons), there is a
brief antibody-negative carrier
state. During this time, the virus reproduces
rapidly until the immune system begins to react and/or
targets are exhausted. HIV RNA or HIV p24 (capsid) antigen
is detectable in plasma, even when no antibody to HIV is
detectable.
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Within 1 to 4
wk after infection, some patients develop acute
retroviral syndrome or primary HIV infection with
fever, malaise, rash, arthralgias, and generalized
lymphadenopathy, usually lasting 3 to 14 days, followed
within days to 3 mo by seroconversion for antibody to HIV.
Acute retroviral syndrome is frequently misdiagnosed as a
febrile upper respiratory illness ("flu") or
mononucleosis.
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Subsequently,
these acute manifestations disappear (although
lymphadenopathy usually persists) and patients become antibody-positive,
asymptomatic HIV carriers. Some of these patients
develop mild, remittent symptoms and signs that do not meet
the definition of AIDS (eg, thrush, zoster, diarrhea,
fatigue, fevers). Leukopenia is common and anemia and
immune-mediated thrombocytopenia may also occur.
Signs &
Symptoms are very broad and escapes the purpose of this
advisory, therefore, we will just mention the following
important locations:
Symptoms
in women
The presentation
and course of HIV infection in women resembles that in men
overall with the exception of chronic refractory vaginal
candidiasis and increased risk of cervical intraepithelial
neoplasia. Some STDs such as pelvic inflammatory disease [PID]
may be atypical, more aggressive, and resistant to treatment in
HIV-infected women. HIV testing for women with recurrent,
aggressive, or unusually resistant STDs or vaginal candidiasis
is recommended. Cardiovascular complications include marantic (thrombotic)
or bacterial endocarditis (especially in IV drug abusers) or a
cardiomyopathy with congestive heart failure. Renal
insufficiency or nephrotic syndrome uncommonly complicates AIDS,
but may be a source of severe disability. |