EPIDEMIOLOGY

1. EPIDEMIOLOGY SAMAR MUSMAR

2. Basic epidemiologic concepts • Epidemiology comes from the Greek words epi, meaning “on or upon,” demos,meaning “people,” and logos, meaning “the study • Defin: the study of factors that determine the occurrence and distribution of dse in a population • One of ways in which dse is studied—4 ways of scientific study of dse: • Sub molecular and molecular—cell biology immunology biochem • Tissue or organ level—anatomic pathology • Individual pt level—clinical medicine • Population level--epidemiology

3. Historical background • Hippocrates--suggested that environmental and host factors such as behaviors might influence the development of disease • John Graunt--in1662,was the first to quantify patterns of birth, death, and disease occurrence, noting male-female disparities, high infant mortality, urban-rural differences, and seasonal variations • William Farr,1880 considered the father of modern vital statistics and surveillance, developed many of the basic practices used today in vital statistics and disease classification • Snow—father of epidemiology—analysis of data for cholera outbreak—mid 19th century • Real science –after wwII

4. Classical/clinical epidemiology • Classical—pop-oriented studies community origins of health problems, nutrition, enviro, human behavior, psychological, social, spiritual. • Interested in finding risk factors • Clinical—use similar research design and statistical tools,but studies pts in healthcare settings in order to improve dx tx and prognosis of pts(already have dse) • Sometimes called—clinical decision analysis

5. Infectious dse epid/ch dse epid • Infectious—heavily depends on lab(micro &serology) • Chronic—heavily depends on complex statistical methods • Not absolute difference • Some inf also considered ch (T.B. HIV )

6. Etiology and natural hx of dse • Natural hx—progression of dse without medical or public health intervention • Stages of dse—predse,latent,symptomatic • Predse—before pathologic process begins—early intervention--? Prevention • Latent stage—dse has begun ,still asympt—screening and institute tx--? Prevention • Symptomatic stage—dse manifestaion—evident—intervention arrest ,slow,or reverse progression--?prevention

7. Mechanisms & causes of dses • Biologic mech, social & environmental causes—contemplating— • e.g diet lifestyle –dyslipidemia • E.g osteomalacia—muslim community?

8. Triad:host,agent,environment • ? 4th—vector • Host: degree individual able to adapt to stressor (resistance) • factors: genetic,nutritional,immune system,and social behavior • Examples • Nutrition immunecompetent/ • Personal hygiene • Agents of dse: Biological,chemical,physical,social & psychological stressors • Environment: social,political,economic,housing,etc • Vector:insects, mosquits

9. Risk factors(BEINGS) • Biologic (gender, age, wt ,bone density) and behavioral(smoking,sexual,ETOH abuse,illegal drug use • Environmental: e.g aircondition—legionaires dse,Lyme dse—env suitable for tick • Immunological—small pox-eradicated(vaccine & herd immunity) • Nutritional—Japanese-American (MI),Burkitt—dietary fibres,Framingham study—high lipid—MI • Genetic factors:population genetics & genetic epidemiology—genetic screening—PKU • Services,social factors,spiritual factors:

10. Ecologic issues in epidemiology • People are seen not only as individuals but members of communities in asocial context • Any action in eco system—reaction(+ve/-ve) • As one factor in eco systems changed—inevitably change others • Examples:reduction of mortality in childhood—increased prevalence of DJD,control of inf dse—increase of another set of dses

11. Vaccination and patterns of immunity • Herd immunity--? • Vaccination program? • Diphteria—vaccine produced immunity is different now from years ago(natural dse--subclinical booster dose)now more susciptable • Diphteria epidemic in NIS of soviet union 1990

12. vaccination • Smallpox: eradication vaccination(variola major,and variola minor) ? Risk • Poliomyelitis:salk1950’s(injectable)—no herd immunity.sabin(oral)1960’s—herd immunity--?eradication. • Palestine(Gaza) salk followed by sabin? • Wild paralytic polio eradicated,only vaccine paralytic polio (USA)—switch to salk • Syphilis:1ry & 2ry stages—herd immunity,partial individual immunity,still pt—goes to latent-3ry stage,abx tx quick response ,but reinfection is v high

13. Sanitation • 19th century—killers—diarheal(children) and T. B(adults) • Sanitation--↓inf mortality rate--↑pop growth • Demographic gap—difference between birth and death rates • ↓inf mortality rate-cause for pop growth and necessity for pop control • Sanitation—affects dse pattern—e.g appearnce of epidemic paralytic polio—(iceberg phenomenon) by decreasing exposure of newborns to subclinical infection—delaying inf to childhood(no longer protected by maternal immunity—upper socioeconomic group –most suffered • Similar is Hep A virus(fecal oral route)—delay of inf to adulthood

14. Vector Control and land use patterns • Subsaharan africa –e.g.of negative effects of good act. • Tse Tse fly control—larger # of cattle—overgrazing—frequent droughts

15. River dam construction and patterns of dse • Aswan dam --↑# of ? • Senga river project-- ↑# of malaria,Rift valley fever, and Denge fever,and schistomiasis • Why?

16. Synergism of factors predisposing to dse • STD’s--++HIV—AIDS—reactivation of latent inf e.g. T.B. • Malnutrition and infection(vicious circuit) • Ecological and genetic factors—new strains of influenza(antigenic shift,antigenic drift)

17. Uses • Population or community health assessment • Individual decisions • Completing the clinical pictureCompleting the clinical picture • Search for causes