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Epidemiology of AIDS

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  1. Epidemiology of AIDS Dana Carr RN.,BHScN, MSc Epidemiology

  2. Outline • HIV virology • Epidemiology • Compare rates in Africa and NA. • Compare modes of transmission • Dry Sex and I TRACK

  3. Human Immunodeficiency HIV • Retro Virus (RNA) • Subgroup Lentvirus (slow) • Inert • Fragile • Protective envelope • Attacks immune system • Invades Helper T cell lymphocytes and macrophages(WBC) • gp120 molecule attaches to the CD4 molecule on the T helper and macro

  4. HIV Virus

  5. Helper T cell the virus enters the nucleus of the WBC • uses the DNA coding to replicate; • T helper cells are destroyed releasing virus • HIV virus entering macrophages replicate and them bud out of an intact cells.

  6. HIV Budding from macrophage

  7. HIV virus attacking T helper cell

  8. HIV the infectious agent • Incubation period –variable 1-15 yrs w/o tx • Transmission- sexual contact (increased risk with ulcerative STD’s , anal), sharing contaminated needles, transfusion, • Reservoir – Human BBF • Communicability – unknown presumed early onset extends through life • Symptoms – opportunistic infection,ARC,AIDS

  9. HIV to AIDS

  10. Global transmission of HIV

  11. What’s in a Name?Definition of Epidemiology • ‘epi’ upon ‘demos’ people ‘logos’- study of • The study of what befalls a people (not the individual) • Oxford Dictionary 1873 “branch of medical Science which treats epidemics” • “epidemic’ related to disease (communicable)

  12. Epidemiology 2002 • “ the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems” • Study – surveillance, observation, research • Distribution ‘ person, place time • Determinants – biological, behavioral, physical, social and cultural • Health related states or events – disease; wellness; behaviors • Specified populations- characteristics • Control of Health – prevention and promotion

  13. Basic science of public health Health and disease do not occur randomly in a population What is the probability of the event occuring and ‘who is at risk?’ Good research methods ‘garbage in ..garbage out’ Exposures and outcomes Probability of event occuring (rate) Comparing (rates) in different populations or the same population at different times Hypothesize why they are different Principles of Epidemiology

  14. Models of disease Transmission • Epidemiological TRIAD Host Intrinsic factors that influence host susceptibility Agent Biological characteristic of agent Environment Extrinsic factors Opportunity for infection to occur

  15. Triad Cont’d - Determinants • Agent factors: pathogenicity; virulence • Host factors: age, gender; education; behaviors; culture • Environmental: climate; geography; biological; socioeconomic, political

  16. Models of Disease ‘Web of Causation’ • Metaphor for the complex, multifactoral causation of disease • communicable and non-communicable

  17. Types of Studies • Descriptive (leads to hypothesis development) • Case study (one unusual case) • Case series • Survey - cross sectional • Analytical Studies (hypothesis testing) • Cohort – compare # case in exposed and unexposed groups • Case- control - compare exposures in cases and non cases • Ecological Studies – study exposure and outcomes in groups or populations (not individuals) eg Selenium and HIV

  18. Incidence vs prevalence • Incidence –the number of NEW events/cases during a given period of time in a specified population (temporal) • Prevalence – the number of events/cases at a designated time in a specified population (snapshot)

  19. Rates….Why use them? • Rate = • the # of events in a specified period population at risk during that time • Rates are proportions • Proportions can be compared • Compare rates of events in different populations and hypothesis why they are different.

  20. Sub sahara Africa 25.4 million Adult Prevalence 7.4% HIV1& HIV2 Mode of Transmission HETEROSEXUAL 70 -90 % new cases Vertical (mom to baby) Life expectancy – short 1-3 yrs (no tx) North America 1.0 million Adult Prevalence 0.3 HIV1 Mode of Transmission MSM (58%) IDU (20%) Life expectancy- 15-20 with tx Living with HIV infectionSub Sahara Africa Vs North America

  21. Think about Triad: host; agent ; environment and how they relate to HIV To what extent does culture ie values beliefs; influence the spread of HIV How does culture impact prevention and control programs

  22. London School of Hygiene and Tropical Medicine (LSHTM) Multicentre Study on FactorsDetermining Differential Spread of HIV in 4 Cities in Sub Sahara Africa • change in HIV prevalence among pregnant women during 10 year period (mid 80’s to mid 90’s) • Cotonou (Benin) 0-0.6% • Yaounde (Cameroon) 1 – 5.5% • Kisumu (Kenya) ? – 25 % • Ndola (Zambia) <5 – 25 %

  23. HIV transmission in Sub-sahara Africa • 10% world population • 2/3 of all people living with HIV • Predominantly heterosexual transmission • Estimate 70 to 90% all new cases • Vertical Transmission

  24. Factors that increase probability of Transmission of HIV • Biological – increase viral load, genital ulceration resulting from STD’s (HSV2) , dry sex practice; sex during menses; anal sex ; lack of circumcision • Behavioral - Sexual partners (consecutive, concurrent); rate of partner change; contact with STW; anal sex; lack of Circumcision; dry sex Think about the overlap of cultural and biological risk factors

  25. Comparison of Prevalence of HIV during 10 yr period

  26. Multi centre study Methodology • Cross sectional survey • Sample population in each city: • Males 600 to 900 • Females approx 1000 • Questionaire interview • Sociodemographic • Sexual behaviors • Specimen collection and phys. examination • Biological RF

  27. Risk Factors Consistently more common in the high HIV prevalence Sites Parameters of Sexual Behavior • young age at first sexual encounter (female) • Young age at first marriage • Large age difference between spouses Co factors in HIV transmission: • HSV- 2 infection • Trichomoniasis (females) • Lack of male circumcision

  28. Risk Factors NOT Consistently more common in the high HIV prevalence Sites Parameters of sexual behavior • High rate of partner change • Sex with sex workers • Concurrent partnerships • Large age difference between non spousal partners Co- factors in HIV transmission • Non-ulcerative STI’s (gono, chlamydia) • Syphilis • Dry sex • Lack of condom use

  29. Everything you wanted to know about Dry Sex….. • Documented in 11 countries in sub-Sahara Africa • The practice of Dry Sex is the use of substances to dry the vagina prior to intercourse • ‘Love Medicine’ women use to please men

  30. Methods • Ingestion - tea or porridge • Insertion – mixed with saliva or cloth • Wiping – cloth or finger • Juju belt – herbs worn around waist • Body smearing substances

  31. Substances used for Dry Sex • Plants: Leaves (cassava, tomatoe); Bark; roots; herbs, • commercial products (soap,detergent salt, toothpaste,vicks) • stones (crushed or powdered) • animal products • Cloth; tissue • icecubes

  32. Culture of Dry sex • Men prefer dry vagina; increase sensation; secretions not desirable; • Women often economically dependant on men • Marital fidelity and stability • Taught to young girls as rites of passage by elders • 13 andn 14yr olds pressured by older men to be sexually active

  33. Dry sex as a RF for HIV transmission • Biological : direct or indirect injury to vaginal wall; • facilitate transmission of HIV from infected male to susceptible female • Portal of entry for HIV • Increase WBC at site ; viral reservoir • Decrease lactobacillus increase risk of HIV transmission • Dry sex deterrent to condom use • Condom breakage due to heat and dryness • Faciltates transmission of virus from infected female to susceptible male ( lower viral load; increase shedding)

  34. Characteristics of Women who practice dry Sex in Ndola, Zambia • 35.4% of women in study ingested substances (only 15 practiced insertion) • Frequency of practice increased with age • Women who were married were more likely to practice dry sex • Only 5.4 % of all women who practiced dry sex used condoms • 35% HIV positve; not significantly assoc with ingestion of substances for dry sex ; • Sample size for insertion too small

  35. Do NA women practice a form of dry sex?? • Douching for example • What else do we do? • Piercing? • Tattooing

  36. Impact of culture in Transmission and prevention. • Dry sex is embedded in their culture • Is discontinuing practice an option? • Condom negates effect of dry sex • What are some options??

  37. Canada Estimates 2002 • Adult Prevalence (15-49) 0.3% • Total cases: 56,000 (46,000 to 66,000) HIV • Heterosexual 10,000 (18%) • High Risk Groups: • MSM- 32,500 (58%) • IDU –11,000 (20%) • Aboriginal -509 (3.1%)

  38. Estimated exposure category distributions (%) among new HIV infections by time period(PHAC HIV/AIDS Epi Update- May 2004)

  39. Aboriginal Population • Aboriginal: only represent 3.3 % of the Canadian population but represent 3.1% of the reported HIV cases. (14.4 % all AIDS case) • over represented in HIV epidemic • IDU key mode of Transmission • Significant impact on Aboriginal women • Infected at younger age than non-Aboriginal

  40. Aboriginal HIV/AIDS Stats

  41. MSM • Risk Behaviors • unprotected anal sex with casual or regular partners • Unsafe sex practice with known HIV –positive partner

  42. Injecting Drug Users • Hi Risk Behaviors • Sharing needles • Sharing equipment • Trading unprotected sex for money and Drugs • incarceration

  43. Enhanced Surveillance of Hi Risk Groups • Prevalence of HIV/AIDS in the general population low and these numbers don’t reflect the prevalence in hi risk groups • enhanced surveillance of high risk groups is required to monitor trends in behaviors and disease • Better able to target prevention and control measures

  44. North America:I TRACK survey • Prevalence low in general population • High risk groups MSM , IDU, Aborginal • Enhanced surveillance in hi risk groups • Target prevention meaures • Consider the ‘cultural issue of IDU; MSM and aboriginal