MID-TERM EXAMINATION

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1 Epidemiology 227 May 2, 2007 MID-TERM EXAMINATION Select the best answer for the multiple choice questions. There are 75 questions and 11 pages on the examination. Each question will count one point. Notify the instructor if your examination does not have 11 pages. Clearly indicate on the scan form the one best answer to each question among the answers provided. Be sure that you have selected your choice correctly on the scan form. Be sure that you have entered your name and identification number on the scan form and filled out the columns for the letters of your name and numbers of your identification number correctly (see front and back). Use a #2 pencil and fill all circles completely. 1. The total number of persons estimated to be living with HIV world wide in December, 2006 was: a. 10 million b. 20 million c. 25 million d. 75 million e million 2. The incidence of HIV infection is highest in which of the following regions of the world? a. Sub-Saharan Africa b. Asia c. South America d. South Asia (India, Pakistan, Bangladesh) e. North America 2. The major risk factor for transmission of HIV in Sub-Saharan Africa is: a. Male to male sex b. Injection drug use c. Heterosexual activities d. Donating of plasma e. Migration 4. Which of the following is the biggest determinant of vertical transmission of HIV from mother to infant? a. Premature birth b. Decreased CD4 counts in the mother c. Advanced clinical disease in the mother d. Viral load in the mother e. Twin babies 5. The majority of orphans from HIV-infected parents are infected with HIV:

2 6. What proportion of HIV-infected adults (>15 years old) are in the year age group in the U.S.? a. 10% b. 25% c. 40% d. 70% e. 85% 7. The reporting fraction refers to: a. The proportion of persons with HIV b. The proportion of persons with HIV who are reported to the health department c. The proportion of the population that is at risk of HIV infection d. The proportion of those infected who are willing to be identified e. The proportion of those infected who are NOT willing to be identified 8. The highest number of HIV infections are occurring in: a. Zimbabwe b. China c. India d. South Africa e. Botswana 9. The highest rate of HIV infection in women is occurring among which ethnic group in the United States? a. African-Americans b. Hispanic-Americans c. European-Americans d. Asian-Americans e. Pacific Islander-Americans 10. The highest proportion of HIV-infected women in the United States are: a. Sex partners of MSM b. Sex partners of injection drug users c. Sex partners of recent migrants from Sub-Saharan Africa d. Injection drug users e. Commercial sex workers 11. In the United States, the rate of AIDS is how many times higher among African- American females than among white, non-hispanic females? a. 2 times higher b. 4 times higher c. 10 times higher d. 25 times higher e. No higher 2

3 12. The leading cause of death among men years in the United States in 2006 was HIV/AIDS: 13. The highest risk of sexual transmission of HIV per act is associated with which of the following activities? a. Oral-genital intercourse b. Vaginal intercourse c. Anal intercourse d. Kissing 14. The ratio of asymptomatic HIV infection to AIDS cases is highest in which stage of an HIV/AIDS epidemic? a. Early stage b. Middle stage c. Later (mature) stage 15. Pooling of sera to reduce the cost of testing is most efficient in: a. Countries with a high prevalence of HIV b. Countries with a low prevalence of HIV c. Countries in which the predominant strain of HIV is clade A d. Countries in which the predominant strain of HIV is clade E e. Countries having sophisticated technology and trained technicians 16. Polymerase chain reaction (PCR) is used to measure: a. Level of CD4 lymphocytes b. Level of CD8 lymphocytes c. Level of CD3 lymphocytes d. Level of HIV-RNA e. Level of HIV-DNA 17. The major barrier to widespread HIV testing in most countries is: a. Lack of funds b. Lack of trained technicians c. Lack of treatment facilities d. Stigma 18. All are true regarding saliva testing for HIV except: a. Good sensitivity and specificity b. Cost-effectiveness can be increased by pooling c. Easy to collect and transport d. High acceptability e. Rapid results 3

4 19. The greatest barrier to treating HIV/AIDS patients in developing countries currently is: a. The cost of the drugs b. Mutation of the virus c. The presence of resistant strains of HIV d. The lack of an infrastructure to deliver the treatment 20. The most important factor in controlling the HIV/AIDS epidemic in a country is: a. Adequate funds b. Commitment of physicians c. Availability of knowledgeable physicians d. Political will of the national leaders e. The subtype of the virus 21. Surveillance systems are NOT useful for: a. Observing trends in disease occurrence b. Observing spread between risk groups c. Establishing the natural history of infection d. Monitoring changes subsequent to initiation of intervention strategiess e. Detecting outbreaks 22. Surveillance systems usually provide information about changing: a. Prevalence of disease b. Incidence of disease c. Death from disease d. Morbidity of disease e. AIDS cases 23. Surveillance focuses on populations, whereas screening focuses on individuals: 24. The objective of behavioral surveillance is: a. To anticipate the future trends of the HIV epidemic b. To measure the level of HIV in the population c. To determine trends in sexual mixing patterns d. a. & c. above e. All of the above 25. Which of the following are the most important components of surveillance? a. Accuracy b. Timeliness c. Action d. a. and c. above e. b. & c. above 4

5 26. The study design most appropriate for surveillance is: a. Case control b. Cross-sectional c. Cohort d. Serial cross-sectional surveys e. Syndromic 27. Which cells can be infected by HIV? a. CD4+ cells b. B-cells c. Macrophages d. Neurons e. CD4+ cells, B-cells, and macrophages 28. Generally speaking, which one of the following is not necessary for HIV to enter target cells at the early stage of HIV infection? a. p41 b. gp120 c. CXCR4 d. CCR5 e. p Which component of the human immune system responds first to antigen stimulation? a. Innate immunity b. Acquired immunity c. Both innate and acquired immunity take about 3-4 weeks d. Both innate and acquired immunity respond within hours 30. Antibodies to HIV viral proteins are made usually within post-infection: a. 4-6 weeks b. 4-7 days c. 4-6 months d. None of the above 31. Which of the following is NOT characteristic of the adaptive immune system? a. Antigen/antibody specificity b. Diversity c. Rapid response d. Immunologic memory e. Self/non-self recognition 32. Which cells are responsible for initially stimulating proliferation of CD4 and CD8 cells? a. NK cells b. B-cells c. Dendritic cells d. Macrophages e. c. & d. above 33. Which type of cell is responsible for killing other cells that are infected? 5

6 a. CD4+ b. CD8+ c. B-cells d. Macrophages e. All of the above 34. The major response of the acquired immune system to a foreign antigen is proliferation of cells: 35. The major immune response to a foreign antigen occurs in which part of the immune system? a. Peripheral circulation b. Oral mucosa c. Genital mucosa d. Lymphoid tissue e. All of the above 36. Why do cytotoxic lymphocytes fail to eliminate HIV-1? a. Epitope escape b. Exhaustion c. Suboptimal CTL d. All of the above e. None of the above 37. To be activated, a T-cell needs: a. Antibodies b. A non-self antigen c. An antigen-presenting cell d. All of the above e. b. & c. above 38. The main function of B-cells is to: a. Stimulate CD4+ cells b. Stimulate CD8+ cells c. Regulate dendritic cells d. Facilitate macrophage activity e. Produce antigen-specific antibodies 39. MHC class-ii antigens are: a. Found on dendritic cells and B-cells b. Recognized by CD4+ cells c. Recognized by CD8+ cells d. a. & b. above e. a. & c. above 40. Clearance of HIV-infected cells is accomplished by: a. Cytokines 6

7 b. CD8+ cells c. CD4+ cells d. MHC II molecules e. Macrophages 41. The level of HIV is highest during the: a. Acute phase of infection b. Subclinical phase c. After AIDS is diagnosed d. Is high during all three phases 42. The long terminal repeat (LTR) component of the HIV encodes the: a. Gag genes b. Pol genes c. Envelope genes d. Lipid outlayer of the virus e. a., b., & c. above 43. Rev, Tat and Nef are: a. Structural genes b. Regulatory genes c. Enzyme genes d. Envelope genes e. Gag genes 44. In which organ do T-cells mature? a. Bone marrow b. Thymus c. Spleen d. Liver e. Bladder 45. The highest numbers of T-cells are contained in the: a. Peripheral blood b. Lymph nodes c. Gut (gastro-intestinal tract) d. Central nervous system e. Anal mucosa 46. The human immune response to HIV fails to eliminate HIV-infected CD4 cells in the quiescent stage: 7

8 47. Antibodies are not effective at neutralizing HIV because: a. Viral envelope protein mutates b. Relevant epitopes are hidden with the HIV c. Gycosylation blocks contact with envelope proteins d. All of the above e. a. & b. above 48. The normal ratio of CD4 cells to CD8 cells is: a. 1:1 b. 2:1 c. 5:1 d. 10:1 e. 100:1 49. Which component of HIV contacts the cell surface first? a. p24 b. gp41 c. gp120 d. Nef e. Tat 50. Which component of HIV contains gp120? a. Core b. Pol c. Envelope d. Endoplasm e. Cytoplasm 51. Which cell receptor site is most frequently used by HIV for initial attachment? a. CCR3 b. CXCR4 c. CCR5 d. CD4 e. Fusin 52. Which of the following enzymes is responsible for conversion of viral RNA to viral DNA? a. Reverse transcriptase b. Integrase c. Protease inhibitors d. Fusionase e. RNA reductase 53. HIV causes dementia by infecting the neurons of the central nervous system: 54. Individuals who respond to HAART tend to show improvement on cognitive measures: 8

9 55. Which of the following statements is correct? a. Almost all new HIV-1 infections are caused by CXCR4-tropic viruses b. Most viral replication occurs in the blood c. Virus can only be transmitted by cell-free virus d. Opportunistic infections result from depletion of the immune response e. gp120 fuses the cellular and viral membranes 56. Which of the following happens in the early stage of productive HIV infection? a. Production by CD4 cells of 100 million to 1 billion HIV virions per day b. Massive destruction of CD4+ cells by HIV-1 and cytotoxic CD8+ cells c. Rapid replacement of CD4+ cells, up to 2 billion per day d. Establishment of dynamic equilibrium between HIV production and CD4+ replacement e. All of the above 57. Current therapies fail to cure the HIV-infected individual because: a. Resistance to the drug b. Toxicity requires cessation of drug c. Failure to clear all the reservoirs of infected cells d. All of the above e. a. & b. above 58. HIV is present in the brains of almost all HIV-infected individuals: 59. Which organism is the most common cause of HIV-related brain infections in the U.S.? a. Papovavirus b. Toxoplasma c. Cytomegalovirus d. Aspergillis 60. The diagnosis of HIV-associated cognitive/motor complex disease is usually made: a. At the time of initial infection b. At the time that antibodies appear and the patient becomes test positive c. During the asymptomatic phase of HIV infection d. Around the time that the first HIV-associated symptoms appear e. 6-8 months after the diagnosis of AIDS has been made 61. Diagnosis of HIV-associated cognitive motor complex requires multiple observations over at least one month of follow-up. 62. HIV-associated cognitive/motor complex disease: a. Causes loss of precision in movements 9

10 b. C\auses decreased interest in work, recreational and social activities c. Is caused by the infection of neuron d. All of the above e. a. & b. above 63. What percent of HIV-infected individuals have evidence of nervous system abnormalities in their brains at autopsy? a. 10% b % c % d % e. 100% 64. HIV dementia is most often confused with a diagnosis of: a. Depression b. Bipolar disorders c. Schizophrenia d. Paranoia e. Low IQ 65. The frequency and severity of HIV dementia is higher in: a. Young individuals b. Middle age individuals c. Older individuals d. Similar in all age groups 66. Which types of vaccine are contraindicated in HIV+ individuals? a. Live attenuated b. Killed c. Recombinant d. DNA 67. Immune reconstitution disease occurs: a. During the acute stage of infection with HIV b. After the diagnosis of AIDS c. Shortly after the initiation of HAART d. When the CD4 level falls below 50 cells per cc e. Just prior to death 68. In HIV+ individuals with tuberculosis, which disease should be treated first? a. Tuberculosis b. HIV c. Treatment should begin simultaneously 10

11 69. HAART eliminates latently infected cells as well as productively infected cells: 70. It is advisable to initiate prophylactic treatment of opportunistic infections at the time that HAART is initiated: 71. The primary therapeutic goal of antiretroviral treatment is to: a. Increase the level of CD8+ cells b. Increase the level of CD4+ cells c. Increase the number of activated B-cells d. Restore the innate immune response e. Decrease the level of HIV 72. Which of the following is the most common opportunistic infection of HIV/AIDS cases in developing countries? a. Toxoplasmosis b. Tuberculosis c. Pneumocystis pneumonia d. Cryptosporodiasis e. None of the above 73. Which of the following was the major cause of deaths in AIDS cases in the U.S. before the advent of HAART? a. Kaposi s sarcoma b. Mycobactarium avium c. Herpes simplex virus d. Toxoplasmosis 74. T-20 is a promising new antiretroviral therapy which acts at the step of : a. Fusion b. Reverse transcriptase c. Integrase d. Protease e. Maturation 75. The leading cause of death in men years in Los Angeles County during was: a. HIV/AIDS b. Unintentional injuries c. Heart disease d. Cancer e. Diabetes 11

5. Over the last ten years, the proportion of HIV-infected persons who are women has: a. Increased b. Decreased c. Remained about the same 1

5. Over the last ten years, the proportion of HIV-infected persons who are women has: a. Increased b. Decreased c. Remained about the same 1 Epidemiology 227 April 24, 2009 MID-TERM EXAMINATION Select the best answer for the multiple choice questions. There are 60 questions and 9 pages on the examination. Each question will count one point.