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VIRUSES
Human Immunodeficiency Virus
Part II
TYPES OF HIV
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There are two types of HIV
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HIV-1 and HIV-2
• Can be distinguished genetically and antigenically
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HIV-1 cause of current worldwide pandemic
• In the United States, unless otherwise noted, the term “HIV” primarily refers to HIV-1
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HIV-2 found in West Africa and rarely elsewhere
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Both types of HIV damage a person’s body by destroying specific blood cells
HIV-1
•
The HIV-1 type
• Most common type
• Differ by geographic distributions
• Is divided into a major group (Group M) and two or more minor groups
• M is for major, and is the most common type
• M group divided into subtypes (A-K)
• All produce AIDS similarly
HIV-2
•
In 1986, a second type of HIV, called HIV-2, was isolated from
AIDS patients in West Africa
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HIV-2 has the same modes of transmission as HIV-1 and is associated with similar opportunistic
infections and AIDS
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In persons infected with HIV-2, immunodeficiency seems to:
• develop more slowly and to be milder
• those with HIV-2 are comparatively less infectious early in the course of infection
• As the disease advances, HIV-2 infectiousness seems to increase; however, compared
with HIV-1, the duration of this increased infectiousness is shorter
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HIV-2 is mostly related to simian immunodeficiency virus endemic in sooty mangabeys
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The first case of HIV-2 infection in the United States was diagnosed in 1987
THE STAGES OF HIV INFECTION
• Phase 1: Asymptomatic or chroniclymphadenopathy
• Phase 2: Symptomatic; early indications of immune
failure
• Phase 3 is AIDS: Characterized by indicator
conditions, such as: CMV, TB, Pneumocystis,
toxoplasmosis, and Kaposi's sarcoma
STAGES CONTINUED
•
Phases 1 and 2 are reported as AIDS if CD4+ T cells <200 cells/µl; Phase 3
always reported as AIDS
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Progression from HIV infection to AIDS:  10 y
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The life of an AIDS patient can be prolonged by the proper treatment of opportunistic
infections
•
People lacking CCR5 are resistant to HIV infection
TRANSMISSION OF HIV
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Unprotected sex with infected partner
•
Contact with infected blood
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Contaminated needles & syringes/other instruments
• Frequently spread among IV drug users
•
Maternal-Infant Transmission
• ¼ ~1/3 of untreated pregnancies pass infection to baby
• Reduced risk of perinatal transmission with prenatal zidovudine (AZT)
• The most common routes of transmission in the US are sexual contact, IV drug use,
and vertical passage from infected mothers to offspring.
• Since 1985, transmission by blood transfusion has been rare due to good testing of
blood supply and heat treatment of plasma products.
HIV SYMPTOMS
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Many people don’t have any symptoms after first becoming infected with HIV
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Some have flu-like illness within 1-2 months after exposure
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Often mistaken for other viral infection
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Fever
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Headaches
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Tiredness
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Enlarged lymph nodes
HIV SYMPTOMS
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More persistent or sever symptoms may not appear for ≥ 10 years or more after infection
(adults)
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Within 2 years in kids born infected
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“Asymptomatic” period varies by persom
•
Some people have symptoms within a few months and others remain symptom free > 10
years
AIDS: MOST ADVANCED STAGES OF HIV
INFECTION
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All HIV infected people with <200 CD4+ Tcells per cubic millimeter of blood
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Healthy adults: CD4+ T cell counts ≥ 1,000
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Also includes 26 clinical conditions
• Most are opportunistic infections
• Often severe and sometimes fatal
• Body can’t fight off certain bacteria, viruses, fungi, parasites, other microbes
HIV/AIDS TREATMENT
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Without treatment, nearly everyone with HIV will get AIDS
•
There's no cure for HIV/AIDS, but a variety of drugs can be used in combination to
control the virus.
• Each of the classes of anti-HIV drugs blocks the virus in different ways. It's best to
combine at least three drugs from two different classes to avoid creating strains of
HIV that are immune to single drugs.
•
Prevention- Health care workers use Universal Precautions:
• Wear gloves, gowns, masks, and goggles
• Do not recap needles
• Risk of infection from infected needlestick injury
is 0.3%