AIDS: Lecture 11, Chapter 5

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AIDS, lecture 11, chapter 5 page 89-115 reader 8 questions on AIDS Epidemiology (3), etiology, transmission, diagnosis, treatment (2)

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

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

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