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AIDS: Lecture 11, Chapter 5

AIDS, lecture 11, chapter 5 page 89-115 reader 8 questions on AIDS Epidemiology (3), etiology, transmission, diagnosis, treatment (2)
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HIV and T cells
-HIV infects primarily vital cells in the human immune system such as helper T cells (to be specific, CD4+ T cells), macrophages, and dendritic cells.
- HIV infection leads to low levels of CD4+ T cells through three main mechanisms:
-First, direct viral killing of infected cells; second, increased rates of apoptosis in infected cells; and third, killing of infected CD4+ T cells by CD8 cytotoxic lymphocytes that recognize infected cells.
-When CD4+ T cell numbers decline below a critical level, cell-mediated immunity is lost, and the body becomes progressively more susceptible to opportunistic infections.
Etiology
Retrovirus - 'reverse transcriptase
Two primary strains:
HIV-1: found throughout the world
HIV-2: found primarily in West Africa
Both strains have several subtypes
Mode of Transmission
unprotected sex
healthcare settings
shared needles or equipment
pregnancy, delivery and breastfeeding
Transmission chart
Once it enters the bloodstream...
T-Helper lymphocyte (T4 or CD4 cell)
Decline of immune system
chart
CD4 as diagnosis
Healthy person has 800-1200 CD4 cells/mm3
CD4 below 200/mm3 produces vulnerability to opportunistic infections and cancers
%CD4 also used to diagnose AIDS - count below 14%
Epidemiology
-HIV infection / AIDS now worldwide
-1988- AIDS had been reported in 138 countries (WHO) and 5 and 10 million individuals were infected with the virus
2008 - prevalence estimated at 33.4 million
-Estimated 20% of infected people in US do not know that they are infected! (Knox, 2008)
-3 epidemiological patterns of transmission:
----Pattern 1 - predominantly among homosexual men, drug users
-----Pattern 2 - heterosexual sex, prostitution, blood transfusions, unsterile injections, preinatally
------Pattern 3 - infection from infected individuals from Patterns 1 and 2 or importation of blood
People living with AIDS 2004
Adults and Children estimated to be living with HIV 2007
Global summary AIDS epidemic 2007
Global estimates for adults and children, 2008
-People living with HIV 33.4 million [31.1 - 35.8 million]
-New HIV infections in 2008 2.7 million [ 2.4 - 3.0 million]
-Deaths due to AIDS in 2008 2.0 million [1.7 - 2.4 million]
Over 7400 new HIV infections a day in 2008
More than 97% are in low- and middle-income countries
About 1200 are in children under 15 years of age
About 6200 are in adults aged 15 years and older,
of whom:
------------almost 48% are among women
------------about 40% are among young people (15-24)
Global estimates 1990-2008
Canada
Until end of 1997 - over 36,000 infections and 16,000 AIDS cases
By 2007 - over 59,000 infections and 20,000 AIDS cases
Infection is almost 5 times greater in males: 49,000 versus 10,000
Treatment
No cure - delay in progression of the disease
HAART
highly active antiretroviral therapy - reduce the amount of virus circulating in blood
Nucleoside reverse transcriptase (RT) inhibitors:
interrupts an early stage of the virus making copies of itself
Protease inhibitors:
interrupts the virus from making copies of itself
Fusion inhibitors:
interferes with ability to enter into cells
Anti-retroviral drugs
Retroviruses
viruses that have RNA instead of DNA
time between HIV and AIDS
More than 10 years for the disease to progress from HIV infection to AIDS
current prevalence of AIDS
33.4 million
20%
of affected individuals in the US don't know they have AIDS
annual deaths
around 2 million
new infections every year
2.7 million
infections a day
7400 new infections a day in 2008
Male vs Female infections in Canada
5 times higher in males 49,000 vs 10,000