Modes of HIV transmission.txt

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  1. Modes of HIV transmission & Prevention of HIV/AIDS
  2. - How have the trends in misconception about HIV/AIDS changed over time?
    o Lowered incorrect answers than 1985. More are aware about the actual ways of HIV transmission. Used to think it was from touching toilet, sharing drinks, kissing
  3. - Three reasons why HAART is not the ultimate panacea for HIV/AIDS
    • o 1. Potential for multi- drug resistance
    • o 2. Important quality of life issues
    • o 3. Unattainable/ hard to get
  4. - Three examples of how antiretroviral therapy benefits prevention
    • o Therapy reduces MTCT ( mother to child transmission)
    • o Past exposure ( PEP) reduces HIV infection from needle stick injuries
    • o Reduces viral load, reduces risk of sexual transmission
  5. - How have HIV infection rates in the U.S. changed in the last 25 years?
    o High prevalence, lower incidence ( stable), because of better drugs
  6. o What can we attribute the decline in infection in the mid-to-late 1980s?
    * New treatments
  7. o Refer to slide Current Challenge in the U.S.; know three potential reasons for the recent increase in infection rates among MSM.
    • * Increase in risky behavior
    • * Reduced concern with advent of HAART
    • * Club drugs
    • * Generational forgetting
  8. - From the 1980s to1990s, what group was targeted for prevention efforts? Why?
    o General population/ risky population due to stigma, limited testing
  9. - Positive prevention is endorsed by whom? It is consistent with ?
    o Joint UN Program of HIV/AIDS
  10. o Know the recommendations for Africa outlined in both the required reading and slides.
  11. - Know the sources of infectious HIV
  12. o HIV is present in which cells?
    • * Macrophages
    • * T helper cells
    • * Lymphocytes
    • * Langerhan cells
  13. o Why can HIV be readily transmitted via some bodily fluids (e.g. blood), but not others (e.g. perspiration) ?
    * Isolated and not highly concentrated- cells are found in blood/ semen, mucosal lining
  14. o High concentrations of HIV are found in which four bodily fluids?
    * Blood, semen, vaginal fluid/ secretions, breast milk
  15. o Is HIV fragile outside of its host?
    * Yes, inactivated by exposure to light, contact w/ soap and water
  16. - From an epidemiologic perspective, why do family members of HIV+ hemophiliacs offer a unique opportunity to study casual transmission of HIV?
    o They didn�t know about HIV status in the 80�s
  17. - Three modes of HIV transmission:
    • 1) Identify the three forms of Blood-to-blood transmission;
    • 1. Transfusion of HIV infected blood products
    • 2. Needle sharing drug injection
    • 3. Accidental needle sticks by healthcare workers

    • o What can be done to prevent these routes of transmission ?
    • * Sterilization, viral inactivation methods
  18. - 2) Sexual transmission
    • o Why is intercourse (vaginal/anal) a good mode of transmission?
    • * Site of macrophages, small tears = susceptible to infection
  19. o What is the approximate risk of male to female transmission of HIV?
    * 2x � 10x
  20. Reasons why one gender is more susceptible to HIV than the ot
    • her
    • * Higher concentration of viral load in semen, vagina has more surface area
  21. o Review slide on oral-genital transmission of HIV
    • * Lower risk, difficult to estimate because of other sex behaviors/cofactors
    • * Cofactors: traumas, ulcers, STI�s, ejaculation in mouth, viral RNA, other oral infections
  22. o Be familiar with the ABC campaign
    • * What do the three letters represent?
    • * Abstain
    • * Be Faithful
    • * Condoms
  23. * Understand the debate over Uganda's success; which group(s) claim success is due to A, B, C ?
    * A) Religious groups B) British Med Journal, Ugandan Aids Control C) Donors ( WHO, USAID)
  24. * A) Religious groups B) British Med Journal, Ugandan Aids Control C) Donors ( WHO, USAID)
  25. * Why can the concept of �collective efficacy� not be readily promoted in a public-health campaign?
    * Requires involvement on every level, including small communities
  26. - 3) Mother-to-child transmission (MTCT) ( Perinatal)
    • o Know the three routes of MTCT.
    • * Intrauterine/ Antenatal- DURING PREGNANCY
    • * Peripartum- DURING LABOR/ DELIVERY
    • * Postpartum- BREASTFEEDING
  27. o Are the preventive measures effective for any of the 3 routes of MTCT?
    • * Hint: refer to limitations of C-sections and formula replacements
    • * C Section reduce risk of transmission- only recommended on high viral load
    • * Giving drugs is cost efficient
    • * Formula replacements are safe
    • o What did the U.S. do in curbing rates of MTCT ?
    • * Routine screening
    • * Use of antiretroviral drugs
    • * Avoid breastfeeding
  28. - Incidence versus Prevalence
    • o Which of the two is a measure of risk? And why?
    • * Incidence because it tells us current rate of spread/ transmission
    • o Prevalence is a function of ���.
    • * Thus, does an increase in prevalence of AIDS reflect an increase in the rate of HIV infection (i.e. incident cases of HIV)?
    • * No, could be because of better treatments
    • * Prevalence higher because living longer
  29. Individual Assessment of HIV Risk
  30. - Know characteristics of the normative model of risk assessment
    o Requires accurately defining risks, calculating and choosing alternative w/ highest expected value
  31. o Do we typically make decisions on the basis of normative models, i.e. by applying laws of logic and statistics?
  32. o If not, how do we assess risk from various probabilities?
    Heuristics- basic rules of thumb
  33. - Heuristics are useful in making what kinds of decisions?
    Quick decision making
  34. o Can the use of heuristics lead to significant biases in decision-making?
    * Yes, because there can be consistent patterns to biases
  35. * Know characteristics of the representativeness heuristic
  36. * More object X is similar to class Y, more likely X belongs to Y , ignores multiple biases
    * We often judge whether object X belongs to class Y by how representative X is of Class Y
  37. * Identify and understand the two representative biases
    • * Misconception of chance
    • o Expect random sequences to be representatively random
    • * Insensitivity to Base Rates
    • o Physicians don�t use it
    • o Judge on description rather than if there are more farmers than engineers, etc
  38. o What are the two main contributors to the availability heuristic?
    • * Familiarity-frequency of an item or event in our memory
    • * Salience- vividness of item or event
  39. o Using the anchoring heuristic, adjustments are typically biased towards which values?
    * Toward initial values, the anchor
  40. o Do we tend to overestimate or underestimate conjunctive events? What about disjunctive events?
    * Overestimate conjuctive ( multiple steps, this and that) events, Underestimate disjunctive ( multiple possibility, this or that) events
  41. * How do we calculate the two events?
  42. * P ( A * B) = P(A) * P(B) � CONJUNCTIVE
    • * P ( A or B) = P(A) + P(B) - DISJUNCTIVE
    • * Examples of the two events
    • * Birthday paradox � disjunctive
    • * HIV ( overestimate needle stick) � conjunctive
  43. o What is the connection between optimistic bias and HIV testing?
    • * Optimistic bias occurs when people tend to believe they are less likely than others to experience harm, personal invulnerability
    • * = underestimate risk for HIV, happens to other people, can�t happen from sexual contact with good people
    • * Characteristics of the late testers
    • * Young ( 18-29 yrs), heterosexual, LESS educated

    - young (optimistic bias?), heterosexual (representativeness heuristic ), less educated (knowledge), and African American or Hispanic (representativeness heuristic ).
  44. o Why can HIV prevention heuristics be misleading?
    • * Causes condom usage only with casual partners
    • * Known partners are safe partners
    • * One marriage is safe
    • * Trusted partners are safe partners
  45. HIV Testing & Surveillance
  46. - What are the relationships between the HIV test and antibodies, viral levels and the window period ?
    o In the 8 week window period, no antibodies test HIV + ( test comes out false negative)
  47. - Approximately what % of the U.S. population has not been tested for HIV? Does this % vary by ethnicity?
    o 42%, YES
  48. - Understand the 2x2 table for screening test outcomes (slide 6)
    • o TP FP
    • o FN TN
    • - Know formulas for sensitivity, specificity, PPV and NPV
    • o Sensitivity = TP / TP + FN
    • o Specificity = TN/ TN+ FP
    • o PPV ( probability of having disease if test is positive, increases with greater disease prevalence, increases with greater specificity of a test, in cases when the disease prevalence is low) = TP / TP+FP
    • o NPV ( prob. of having disease given neg. test results) = TN / TN + FN
  49. o What is the trade-off between sensitivity and specificity?
    • * Sensitivity = may be more FP
    • * Specificity= may be more FN
  50. - What are the two stages in HIV sequential testing?
    o #1 ) very sensitive ( ELISA) #2) W Blot: very specific
  51. o Know characteristics of the tests used in both stages
  52. * Less invasive, expensive
    * Very specific W Blot
  53. o Sequential testing yields a higher net sensitivity or higher net specificity?
    * Higher net sensitivity, lower net specificity
  54. - In what setting are we more interested in predictive values (PPV/NPV)?
    o Clinical setting
  55. - Unlike sensitivity and specificity, predictive values are a function of the characteristics of the population
  56. o How does this concept relate to efficiency in screening programs?
    * More efficient in populations at greater disease risk
  57. - Rapid/home HIV testing
    • o Identify three benefits of rapid HIV testing
    • * More get results ( increase receipt of test results)
    • * Increases identification of HIV + pregnant women
    • * More testing in ER
  58. o Approximately how many U.S. citizens are unaware of their HIV infection?
    * 300,000 citizens
  59. o Who are the likely consumers of home HIV tests?
    * Affluent consumers, wealthy, worried well, primarily serionegative ( to be sure), new couples, recent high risk exposure ( binge drinkers, one night stand), persons seeking confirmation
  60. o What are the problems with home HIV testing?
    • * People who need it most can�t afford it
    • * No counselor
    • * Lower PPV as a result of lower HIV prevalence
    • * Does not detect in the window period
    • * More FP + FN, undectected HIV pool is now larger
    • * Impede access to care for people who need it most
  61. - Why do we need to use PCR testing of infants born from HIV+ mothers?
    o Babies can have mom�s antibodies, chance of FP
  62. - In 2006, the CDC recommended a switch to the opt-in or opt-out testing of individuals in a clinical setting? Opt out
    • o Why is one recommended over the other?
    • * Less anxious about testing
    • * Thought it indicated high risk behavior
  63. - Review the process by which an HIV test is first reported, and then forwarded to local and state health departments
    • -
    • - Why is HIV/AIDS surveillance so important?
    • o Monitor trends
    • o Target HIV prevention + treatment
    • o Provides data for funding ( Ryan White)
  64. - Compare and contrast confidential versus anonymous HIV testing
    Confidential = fake name secretely, Anonymous= no name taken
  65. Global Aspects of HIV/AIDS- Part I
    • - What region of the world has the highest concentration of HIV?
    • o Sub-Saharan Africa
    • o In sub-Saharan Africa, 3 countries bear the brunt of the disease -- Swaziland, Botswana and Zimbabwe. One out of every three
    • o adults is infected in these countries.
    • o
  66. - Know the global transmission of HIV as described in slide #5
    • o US- MSM, - moved into drug using population
    • o Sub-Saharan- heterosexual sex
    • o SE Asia, India, China, Former Soviet Union- brothels, prostitution, IV drug users, male drug users infected female sex workers
  67. - Know potential explanations for variation of HIV prevalence throughout Africa.
    • o Why is HIV prevalent in sub-Saharan Africa?
    • * Sex partners ( debunked), High Risk, Low mix Theory, Long term, concurrent sexual relationships
    • * Prostituion -> migrant workers -> general population
  68. o Understand concept of concurrent, �transactional� relationships
    • * Sex from boyfriends for gifts
    • * Could be riskier than prostitution
  69. o Why is HIV less prevalent in West and North Africa?
    * Circumcision, monitoring sexual behavior
  70. - What is the distribution of HIV/AIDS by gender, stratified by region?
    • o Children- 6%, Men- 49%, Women-45%
    • o Worldwide prevalence, prevalence in sub-Saharan Africa, prevalence outside of sub-Saharan Africa
  71. - Explanations for why women have a higher prevalence of HIV than men
    • o Nature of transactional/ polygamous relationship
    • * Fewer men in sexual network
    • * Older men have more economic resources
    • * Women have limited say and social power
    • * Prostitie -> migrant workers -> spouses
    • * Biological factors- women are more vulnerable to heterosexual transmission
    • * Virgin myth
  72. - What is HAART?
    • o Highly Active Anti-Retroviral Therapy -> slows rate at which virus multiples
    • o Typically includes 3 drugs from at least two different classes
    • * Protease inhibitors
    • * Reverse transcriptase inhibitors nucleoside and/or non-nucleoside
  73. - Why do we consider Brazil's response to HIV/AIDS a success story?
    • o Mid 1990�s. 1% or about ? million people were HIV+
    • o Built AIDS clinics, but couldn�t afford to fund HAART
    • o Suit bought against government for access to the antiretroviral drugs
    • * Brazil passed law guaranteeing access to HIV drugs to all citizens who need them
    • * Generic drugs
    • * Pharmaceutical companies engage in R&D to exchange for patent privileges
    • o With limited resources, how did their government obtain expensive HIV drugs?
    • * They made generic HIV dtugs
    • o Is treatment cost-effective in the long-term? Yes, 40-80% decrease in morbidity/ mortality
    • * 85% decrease in hospitalization
    • o How does Brazil's response contrast with how the South African government dealt with HIV?
    • * Limited prevention- only approach, denial of HIV/AIDS
  74. * As a consequence of their policies, what has happened to South Africa's life expectancy?
    Dropped to less than 50
  75. * What age group in South Africa has been disproportionately affected by HIV/AIDS?
  76. - What did Thailand do in the early 1990s to control the spread of HIV?
    • o Condom campaign
    • o
    • - Review importance of healthcare infrastructure for treating HIV patients
    • o Critical need for labs, equipment and well trained personnel
  77. o Distribution of HIV drugs without proper care/instructions can lead to �..
  78. * Multidrug resistance- because of failing to adhere to regimen
  79. Living with AIDS: Individual and Societal Issues
    • - Review debate of individual rights vs. public health in the decision to close bathhouses in San Francisco
    • o Thought it was an antigay movement (public comndemnation of style)
    • o Delayed closing of public baths
    • o Opposition to informational brochures in the bathhouse
    • o Delayed full articulation of transmission modes
  80. - What governments have been slow in accepting the reality of HIV/AIDS?
    • o South Africa, USA
    • - What is the pertinence of the Americans with Disabilities Act (1990)?
    • o disability is defined as a physical and mental impairment
    • o no discrimination in public goods, etc, ( jobs, etc)
    • - How has the perception of HIV/AIDS as an urgent health problem in the U.S. changed over time?
    • o Gone down- decreased as an urgent problem, 44% in 95 to 17% in 06
    • - Do most people today feel that the U.S. government spends too little or too much on HIV/AIDS?
    • o Too little- 63%
    • o What is the perception in relation to other diseases?
    • * too low- compared with cancer and heart disease- 48%
    • o Using a crude measure, such as expenditures/death, how does HIV/AIDS compare to other diseases?
    • * More expensive , spend more but more deaths
    • - Contrast the public's view on U.S. foreign spending (in general) versus U.S. foreign spending on HIV/AIDS
    • o 62% think that we spend too much on foreign aid in general, but 60% think we�re responsible to spend money for HIV worldwide
    • o
    • o Has our view on foreign spending on HIV/AIDS changed over time?
    • * Increased from 44% in 02 to 60% in 06
  81. o What country contributes the greatest share to international AIDS assistance?
    * US at 40.3%
  82. - Review the Ryan White CARE Act (1990)
    • o Treatment to those that can�t afford it
    • o Comprehensive AIDS Resource Emergency
    • o In 1990, the act passed Congress ( vote: 402 to 4)
    • o It is the United States largest federally funded program for people living with HIV/AIDS
    • o Goal is to improve availability of care for those ( HIV+) with low income
    • o Payer of last resort
  83. - Review explanations for why women are especially susceptible to contracting HIV (note: some overlap with prior lecture)
    • o Biological- more virus in semen
    • o Forced to enter into sex work and/or barter sex for food, shelter and safety
    • o Sex workers at high risk for infection
    • * Can�t negociate with clients who refuse to wear condoms, especially if work is illegal
    • * Little choice
    • * Rape, sexual slavery
    • * Culture- men to have multiple extramarital relationships
    • * Cultural norms may deny women knowledge of sexual health
    • * Social pressure to bear children
    • * Women may be unaware of or unable to discuss male partner�s HIV risk
  84. o Why are public health advocates particularly hopeful of the vaginal microbicides?
    • * Can be used without male partner consent
    • * Useful when can�t be used, IE when sex workers is covert ( secret, ninja)
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Modes of HIV transmission.txt
2012-03-20 04:18:27

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