Biology 45- AIDS Fundamentals (Chapter 7-12)

Biology 45- AIDS Fundamentals (Chapter 7-12) - Biology 45:...

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Unformatted text preview: Biology 45: AIDS Fundamentals (Chapters 7-12) Chapter 7: Modes of HIV Transmission and Personal Risk Factors Theoretical biological analysis and empirical epidemiological analysis assign different risk levels to activities o Theoretical Analysis : considers the biological plausibility of HIV transmission for particular activities based on the presence or absence of substances containing HIV and of receptors for these substances Threshold Analysis can be used to make predictions about no-, low-, or high0risk activities These predictions ultimately can be tested by empirical epidemiological data o Epidemiological Evidence can provide the initial evidence that certain activities are or are not associated with HIV infection risk At the outset of the AIDS epidemic, it was epidemiological studies that led to the identification of likely modes of HIV transmission It is important to focus on the behaviors as a causal factor, not the group association Biological Bases of HIV Transmission The HIV virus is actually quite fragile in the external environment and dies quickly when exposed to room temperature and air conditions Sources of Infectious HIV Macrophages and T helper lymphocytes are susceptible to infection by HIV Macrophages may be the long-term reservoirs of HIV in infected individuals because they are not killed by the virus; they circulate throughout the bloodstream, and are found in all mucosal linings of the body Langerhans cells can also be infected with HIV, found in the mucosal surfaces and below the surface of the skin HIV can be isolated relatively easily from blood, semen, and vaginal/cervical secretions The current scientific view is that body fluids and products other than blood, semen, vaginal/cervical secretions, and breast milk contain so little, if any, HIV that they are not of major importance in HIV transmission between individuals Blood, semen, vaginal/cervical secretions, and breast milk contain high numbers of live cells The other body fluids and products (saliva, tears, perspiration, urine, and feces) are completely or nearly completely free of live cells Because live infected cells produce HIV, we expect fluids with live cells to have higher concentrations of HIV Stability of HIV For transmission of HIV infection to occur, infectious virus must survive long enough to pass to a susceptible person and infect target cells Since the HIV virus is so fragile, the virus quickly becomes inactivated when exposed to the drying effects of air or light, and quickly inactivated by soap and water In blood and semen, cells maintain infectious HIV as long as they themselves are alive Target for HIV Infection HIV infection requires the presence of virus receptors on the cell surface T helper lymphocytes, macrophages, and the Langerhans cells are the most abundant in the blood Modes of HIV Transmission Activities Not Associated with HIV Transmission: Casual Contact...
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This note was uploaded on 04/13/2008 for the course BIO SCI 45 taught by Professor Pickus during the Winter '08 term at UC Irvine.

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Biology 45- AIDS Fundamentals (Chapter 7-12) - Biology 45:...

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