3 hiv presentation[1]
TRANSCRIPT
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WHAT IS HIV? Human immunodeficiency virus (HIV) is a lentivirus (a
member of the retrovirus family) that causes acquired
immunodeficiency syndrome (AIDS), a condition in
humans in which the immune system begins to fail,
leading to life-threatening opportunistic infections.
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A virus is not a cell, but is madeup of genetic instructionscontained in a protective shell.
A single HIV virus particle iscalled a virion. It is spherical andone 10,000th of a millimeter indiameter.
The protective shell of the virus isknown as the viral envelope. It is
composed of two layers of fattymolecules.
Embedded in the envelopesurface is complex HIV proteincalled the env protein that sticksout of the envelope surface.
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Env consists of a cap
called gp120 and a stemcalled gp41.
The viral core is called thecapsid.
Major elements within theviral core are:
Two single strands of HIVRNA. RNA carries geneticinstructions that allow the
HIV virus to replicateitself.
There are enzymes thatare needed for replicationof the virus.
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Infection with HIV occurs by the transfer of blood, semen,
vaginal fluid, pre-ejaculate, or breast milk. Within these
bodily fluids, HIV is present as both free virus particles
and virus within infected immune cells. The four major
routes of transmission are unsafe sex, contaminated
needles, breast milk, and transmission from an infected
mother to her baby at birth (Vertical transmission).
TRANSMISSIO
N
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Screening of blood products for HIV has largely
eliminated transmission through blood transfusions
or infected blood products in the developed world.
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There are two strains of HIV known to exist: HIV-1 and
HIV-2. HIV-1 is the virus that was initially discovered
and termed LAV. It is more virulent, relatively easily
transmitted, and is the cause of the majority of HIV
infections globally. HIV-2 is less transmittable and islargely confined to West Africa.
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Species Virulence Transmittability Prevalence Purportedorigin
HIV-1 High High Global CommonChimpanzee
HIV-2 Lower Low WestAfrica
Sooty
Mangabey
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HIV-1 Subtypes Three groups of HIV-1 have been identified on
the basis of differences in env: M, N, and O.
The new one has been classified P. The N and Ovariants are extremely rare.
Group M is the most prevalent and is subdividedinto eight subtypes
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PATHOPYSIOLOGY: HIV causes AIDS by depleting CD4+ T helper
lymphocytes (a subset of T cells). This weakens the
immune system and allows opportunistic infections.T lymphocytes are essential to the immune response
and without them, the body cannot fight infections
or kill cancerous cells. The mechanism of CD4+ T cell
depletion differs in the acute and chronic phases.
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Tuberculosis (TB)
Bacterial pneumonia
Mycobacterium avium complex (MAC)
Salmonellosis
Bacillary angiomatosis (Bartonella henselae bacteria)
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Cytomegalovirus (CMV)
Viral hepatitis
Herpes simplex virus (HSV)
Human papillomavirus (HPV)
Progressive multifocal leukoencephalopathy (PML)
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Candidiasis
Cryptococcal meningitis
Parasitic infections:
Pneumocystis carinii pneumonia Toxoplasmosis
Cryptosporidiosis
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Wasting syndromeNeurological complications
Other complications:
Kaposi's sarcoma
Non-Hodgkin's lymphoma
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Stage I: HIV infection is asymptomatic and not categorized asAIDS
Stage II: includes minor mucocutaneous manifestations and
recurrent upper respiratory tract infections
Stage III: includes unexplained chronic diarrhea for longerthan a month, severe bacterial infections and pulmonarytuberculosis
Stage IV: includes toxoplasmosis of the brain, candidiasis ofthe esophagus, trachea, bronchi or lungs and Kaposissarcoma; these diseases are indicators of AIDS.
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HIV RESISTANCE
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TREATMENT There is currently no vaccine or cure for HIV or AIDS.
The only known methods of prevention are based on
avoiding exposure to the virus or, failing that, an
antiretroviral treatment directly after a highly significant
exposure, called post-exposure prophylaxis (PEP). PEP
has a very demanding four week schedule of dosage. Italso has very unpleasant side effects including diarrhea,
malaise, nausea and fatigue
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Current treatment for HIV infection consists of
highly active antiretroviral therapy, or HAART.
Thishas been highly beneficial to many HIV-infectedindividuals since its introduction in 1996, when theprotease inhibitor-based HAART initially became
available. Current HAART options are combinations(or "cocktails") consisting of at least three drugsbelonging to at least two types, or "classes," ofantiretroviral agents. Typically, these classes are twonucleoside analogue reverse transcriptase inhibitors(NARTIs or NRTIs) plus either a protease inhibitoror a non-nucleoside reverse transcriptase inhibitor(NNRTI).
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HAART neither cures the patient nor does it uniformly
remove all symptoms; high levels of HIV-1, often
HAART resistant, return if treatment is stopped.
Moreover, it would take more than a lifetime for HIV
infection to be cleared using HAART. Despite this, many
HIV-infected individuals have experienced remarkable
improvements in their general health and quality of life,
which has led to a large reduction in HIV-associated
morbidity and mortality in the developed world.
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In the absence of antiretroviral therapy, the median
time of progression from HIV infection to AIDS is
nine to ten years, and the median survival time after
developing AIDS is only 9.2 months. However, the
rate of clinical disease progression varies widely
between individuals, from two weeks up to 20 years.
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Despite the success of highly active antiretroviral therapy(HAART) in controlling HIV infection and reducing HIV-associated mortality, current drug regimens are unable tocompletely eradicate HIV infection. Many people on HAARTachieve suppression of HIV to levels below the limit ofdetection of standard clinical assays for many years.However, upon withdrawal of HAART, HIV viral loadsrebound quickly with a concomitant decline in CD4+ T-Cells,which, in most cases, absent a resumption of treatment, leads
to AIDS
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