Download Module 1: HIV/AIDS: The Epidemic

Chapter 2:
The Path from HIV to AIDS
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HIV is a virus that infects only humans and creates a deficiency in
the body’s immune system
HIV belongs to a family of viruses called retroviruses
Because retroviruses mutate very quickly, a person’s immune
system does not have any defenses against the new version of the
new virus
HIV also belongs to a subfamily of retroviruses called lentiviruses,
which are viruses that have a long delay between the time they
initially infect a person and the time the person starts to show
symptoms
Module 1, Chapter 2
The Structure of HIV-1
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The Viral Envelope: The outer coat
of the virus is called the viral
envelop which is composed of two
layers of fat molecules
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The Spikes: The complex proteins
that protrude through the surface of
the viral envelope are called spike;
they are HIV’s landing gear,
attaching the virus to a host cell
and fusing the two together
The Capsid: The bullet shaped
core of the HIV particle is the
capsid which surrounds two single
strands of HIV’s genetic material
(RNA-ribonucleic acid). Each
strand of the RNA has a copy of
the virus’s genes
Reverse Transcriptase: This is an
enzyme that allows HIV’s RNA to
change into DNA so that it can
pass into the host cell’s nucleus to
begin reproducing itself
Module 1, Chapter 2
What Happens After HIV Infects Cells?
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Once HIV enters the body, it replicates rapidly and
spreads widely
Two to four weeks after exposure, most HIVinfected people suffer flu-like symptoms, as
their immune systems fight off the initial HIV
infection
This first immune response may dramatically reduce
HIV levels
As a result, the number of CD4+ T-cells in a person' body may rebound
after the first, acute infection, and may even approach their original levels
The HIV+ person may then remain free of HIV-related symptoms for years
The virus continues replicating in the organs and tissues of the body’s
lymphatic system where it may not be readily detectable in the blood stream
Eventually, HIV overwhelms the person’s system and large quantities of the
virus enter the blood stream
Module 1, Chapter 2
Why do HIV Infections Almost Always
Progress to AIDS?
HIV eludes the immune system so that the body stops
fighting it
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HIV’s many mutations make some of its particles invisible to
the body’s immune system
HIV damages the immune system, so that the body
can’t fight it
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Over time there are not enough healthy CD4+ cells to defend
the body against infections
When the immune system is so weak that it can no longer
defend against opportunistic infections, a person now has
Acquired Immune Deficiency Syndrome (AIDS)
Module 1, Chapter 2
Diagnosing HIV Infection
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Main Types of HIV Tests
ELISA: Enzyme-Linked
Immunosorbent Assay which
determines if HIV antibodies' are
present in blood or oral fluids
Western Blot: A highly specific
supplemental test that is used for
confirming the ELISA test because it
hardly ever gives a false positive
result
Rapid HIV tests: Saliva-, urine-, and
home HIV antibody testing kits
provide results in as little as 20
minutes
HIV RNA tests: Diagnose HIV
infection very early, before
antibodies are even formed
Module 1, Chapter 2
The Stages and Symptoms
of HIV Disease
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Primary Infection
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The first stage of HIV disease
 2 to 4 weeks after infection, 87% of HIV+
persons suffer flu-like symptoms for a few days
(this sickness is called acute HIV syndrome)
 It usually takes 6 to 12 weeks for the immune
system to develop antibodies to fight the virus,
meaning that a newly infected person may not
test positive for HIV
 Seroconversion is the time when the body
begins producing antibodies, this can take up
to 6 months
Module 1, Chapter 2
The Stages and Symptoms
of HIV Disease
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Chronic HIV Infection
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Asymptomatic Period
 Also called clinical latency – a time when a person has no signs or
symptoms of HIV disease
 Although individual’s show no symptoms at this time, their immune
system’s are already suffering from the presence of HIV; the virus is
actively multiplying and infecting and killing immune system cells
 Immune System Decline
 The more HIV a person has in his or her body (the higher the
plasma viral load) the lower his or her number of health-protecting
CD4+ cells; ultimately resulting in the rapid decline of a person’s
immune system functioning
Module 1, Chapter 2
Immune System Decline
Mild, Non-specific Symptoms
 When the immune system is
damaged, people begin to
experience mild symptoms
 Swollen lymph nodes
 Fatigue
 Weight loss
 Frequent fevers and
sweats
 Frequent or persistent
yeast infections
 Persistent skin rashes
 Shingles
Module 1, Chapter 2
Advanced HIV Disease / Clinical AIDS
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The Centers for Disease Control and Prevention (CDC) has two different
sets of criteria for diagnosing AIDS
CDC AIDS Criteria: Set 1
An HIV infection, confirmed by testing, plus a CD4+ T-cell count of less
than 200 per cubic millimeter of blood (healthy adults usually
have CD4+ T-cell counts of 1,000 or more)
CDC AIDS Criteria: Set 2
An HIV infection, confirmed by testing, plus one of 26 clinical
conditions, primarily opportunistic infections that do not normally
affect healthy people, including certain kinds of pneumonia or
tuberculosis (PCP)
Module 1, Chapter 2
Opportunistic Infections
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Opportunistic Infections are infections that are caused by bacteria,
funguses, or viruses that do not cause disease in people with
healthy immune systems, for example:
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Pneumocystis Carinii Pneumonia (PCP) (a kind of pneumonia)
Kaposi's Sarcoma (KS) (a kind of cancer)
HIV wasting syndrome (extreme weight loss)
Non-Hodgkin's lymphoma (a kind of cancer)
HIV encephalopathy (AIDS Dementia)
Candidiasis (Yeast Infection) of the trachea, bronchi, or lungs
Candidiasis (Yeast Infection) of the esophagus
Module 1, Chapter 2