iNTRODUCTION TO EPIDEMIOLOGY-1.ppt

Biological Weapons Proliferation Prevention Program Introduction to Epidemiology  Learning Objectives Define Epidemiology Summarize the epidemiologic approach List the uses of Epidemiology Describe the interactions between host...

Biological Weapons Proliferation Prevention Program Introduction to Epidemiology  Learning Objectives Define Epidemiology Summarize the epidemiologic approach List the uses of Epidemiology Describe the interactions between host, agent, and environment 2  Epidemiological Principles Diseases (or other health events) don't occur at random Diseases (or other health events) are related to environmental and individual characteristics that vary by  Person  Place  Time 3  Epidemiology Epi = upon Demos = population Logos = study of 4  Definition of Epidemiology The study of the distribution and determinants of health-related states or events in specified human populations and its application to the control of health problems – Dictionary of Epidemiology 5  Key Word: Study The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Study  Basic science of public health 6  Key Word: Distribution The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Distribution  Time, place, person 7  Key Word: Determinants The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Determinants  Cause, risk factors 8  Determinants Hallmark = Comparison group  Any group to which the index group is compared  Persons without disease or who have had no contact with the causal effect Example: 30 of 100 people became ill. What made these 30 individuals ill?  All 30 breathed the air.  All 30 drank the water.  All 30 ate fish. 9  Key Word: States or Events The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. States/events  Not limited to infectious diseases 1 0  Key Word: Population The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Population  Public health 1 1  Key Word: Application The study of the distribution and determinants of health related states or events in specified human populations and its application to the control of health problems. Application  Information for action 1 2  Medicine vs. Epidemiology Clinical Medicine Epidemiology Focus Individuals Populations Main Goal Diagnosis and Prevention and Treatment Control Questions What is wrong with What are leading this patient? causes of illness, What treatment is death or disability in appropriate? this population? What can be done to reduce them? 1 3  Scientific Method Applied to Patient and Community Step Clinician Epidemiologist Data base History, Surveillance, physical exam descriptive epi Assessment Differential dx Inference Hypothesis Diagnostic studies Analytical epi testing Community Action Treatment intervention 1 4  Uses of Epidemiology Determine the magnitude of disease and trends over time Identify the etiology or cause of disease Determine the mode of transmission Identify risk factors or susceptibility Determine the role of the environment Evaluate the impact of the control measures 1 5  Epidemiologist Core Functions Public health surveillance Investigation Data analysis Evaluation Communication Management and teamwork 1 6  Basic Epidemiologic Approach Observe Count cases (events) Describe Descriptive Epidemiology  Time, place, person  Calculate rates Compare rates Analytical Develop hypothesis Epidemiology Test hypothesis Implement actions (control, prevention) 1 7 Biological Weapons Proliferation Prevention Program Epidemiology and Disease  Levels of Disease Increasing amount of disease Pandemic Epidemic Endemic Sporadic 1 9 Epidemiologic Triad 2 0  Host, Agent, Environment Host Agent Environment Age Biologic Disease vectors Microorganisms Sex Population density Chemical Toxins Religion Air quality Physical Trauma SES Weather Nutrition Exercise Noise Behavior Food and water sources Co-morbidity Genetics 2 1  Host, Agent, Environment Host Agent Environment Age Biologic Disease vectors Microorganisms Sex Population density Chemical Toxins Religion Air quality Physical Trauma SES Weather Nutrition Exercise Noise Behavior Food and water sources Co-morbidity Genetics 2 2  Host, Agent, Environment Host Agent Environment Age Biologic Disease vectors Microorganisms Sex Population density Chemical Toxins Religion Air quality Physical Trauma SES Weather Nutrition Exercise Noise Behavior Food and water sources Co-morbidity Genetics 2 3  Chain of Infection Route of Susceptible Host Reservoir Transmission (via portal of entry) Agent 2 4  Reservoir Habitat in which the disease normally lives and multiplies People - Symptomatic - Smallpox - Asymptomatic - HIV Animals (Zoonoses) - Brucellosis - Plague Environmental - Histoplasmosis - Legionnaires’ bacillus 2 5  Route of Transmission Direct  Contact - Cutaneous Anthrax, Hookworm  Droplet –Smallpox Indirect  Airborne – Histoplasmosis, Inhalation Anthrax  Vehicle-borne food or water - Salmonella  Vectorborne  Mechanical – Shigella by fly limbs  Biological – Malaria (maturation) 2 6  Host A person or other living organism that is susceptible to or harbors an infectious agent under natural conditions The host may or may not get the disease Many different factors influence how the disease effects the host:  Immunity  Genetic makeup  Levels of exposure  Fitness of the host 2 7  Smallpox Chain of Infection Droplet Droplet Droplet Droplet 2 8  Smallpox Chain of Infection V Droplet a Droplet c c i n e 2 9  Chain of Infection - Plague Route of Susceptible Host Reservoir Transmission (via portal of entry) Agent 3 0  Do you need to identify the agent to control it? Disease Control Year Agent Year measure Scurvy Diet 1753 Vitamin C 1928 Pellagra Diet 1754 Niacin 1924 Smallpox Vaccination 1798 Orthopox 1958 virus Cholera Water 1849 Vibrio 1893 quality cholerae Yellow Mosquito 1901 Flavivirus 1928 fever control 3 1  Epidemiologic transition: Public Health Response Shift in primary emphasis of public health priorities…. from: microbiologic investigation of communicable diseases to: the etiologic role of behavioral and environmental risk factors 3 2  Why have chronic diseases increased in importance? Favorable demographic changes and public health successes during the 1900’s (quality and availability of food, water, housing, sanitation; communicable disease control) “Epidemic transition” (i.e. change)  Lower overall death rate  Greater life expectancy  Shift in major causes of death: Infectious to non-communicable 3 3  Epidemiologic Transition: Life Expectancy in U.S. 1900 2000 Infant mortality Infant mortality 150.0 deaths /1000 6.9 deaths /1000 live births live births Life expectancy Life expectancy 47 years 76.9 years 3 4  Epidemiologic Transition: Leading Causes of Death in U.S. 1900 2000 1. Pneumonia/Flu 1. Heart disease (202 deaths/100,000) (258 deaths/100,000) 2. Tuberculosis 2. Cancer (194 deaths/100,000) (201 deaths/100,000) 3. Gastro/Enteritis 3. Stroke (143 deaths/100,000) ( 61 deaths/100,000) 5. Accidents ( 36 deaths/100,000) 3 5  Epidemiologic Transition: Actual Causes of the Causes of Death, U.S., 2000 Actual Cause of Cause 1. Tobacco (18%) 2. Poor diet, physical inactivity (17%) 3. Alcohol consumption (4%) 4. Microbial agents (3%) 5. Toxic agents (2%) 6. Motor vehicle (2%) 7. Firearms (1%) 3 6  Current Scope of Epidemiology  Infectious diseases  Chronic (non-contagious) diseases  Injuries (intentional and unintentional)  Environmental and occupational health  Disabilities, e.g., birth defects  Maternal / child health  Behaviors / lifestyle issues  Other 3 7  Defining characteristics of chronic diseases Uncertain etiology (causation) Multiple risk factors Long latency period Non-contagious origin (non-communicable) Prolonged course of illness Functional impairment or disability Incurability 3 8 Chronic Disease vs. Infectious Disease How might data patterns for person, place, and time-specific variables differ for Chronic Disease and Infectious Disease? 3 9  Basic Epidemiologic Approach Observe Count cases (events) Describe Descriptive Epidemiology  Time, place, person  Calculate rates Compare rates Analytical Develop hypothesis Epidemiology Test hypothesis Implement actions (control, prevention) 4 0 The art of epidemiological thinking is to draw conclusions from imperfect data George W. Comstock 4 1  Reference books  CDC, Principles of Epidemiology, 3rd ed.  M. Gregg, Field Epidemiology, 2nd ed.  R. Timmreck, An Introduction to Epidemiology 4 2 THANKS FOR LISTENING 4 3