Principles of Dse Prev and Control

Disease Prevention and Control

Basic Concepts, Natural History, and Principles of Disease Prevention and Control

June 21, 2011 Dr. Paredes

COURSE INTRODUCTION Course Objective:  Acquired knowledge and skills related to the basic principles and strategies in health promotion and maintenance, disease prevention, and control Course Specific Objectives:  Explain the natural history of disease  Discuss the factors contributing to the initiation and progress of the disease process  Discuss various prevention and control strategies applicable at the different stage of a disease process, for the individual, for the family and the community  Assess the state of health of families and communities, using appropriate measurements tools  Discuss selected government programs relevant to current public health concerns of our country Definitions: 1. Preventive Medicine  The science and the art of prolonging life, promoting & maintaining health, and preventing the occurrence of diseases. improving the health of groups of people  Basic science used in Preventive Medicine is Epidemiology.  Is this a specialty? Yes. There are schools offering courses on preventive medicine and masters of public health (specialty in the states ). It is also incorporated in all specialties. 2. Curative Medicine  Part of medicine that restores health and rehabilitates individual patients 3. Public Health  “The art and science of preventing disease, prolonging life and promoting physical health and efficiency through organized community effort” & systematic social action. with the participation of the groups of people  In public health, we are more concerned with HEALTHY individuals 4. Community Medicine  Concerned with the social, cultural, biologic and environmental factors that determine the state of health and problems of the community, propose sollutions and services  Common concern: promotion of health and prevention of illness  concerned with people who are healthy: how we can keep them healthy for the rest of their lives 5. Family medicine  a medical specialty concerned with the comprehensive and continuing health care for individuals and their family, encompassing all ages, sexes, each organ system and every disease entity –American Academy of Family Physicians (2005)  family is the basic unit of community medicine  considered a specialty LECTURE PROPER I. Preventive Medicine II. Epidemiology III. Public Health A. Concerns of Public Health B. modern Public Health C. 10 essentials of public health service IV. Community Medicine

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I. PREVENTIVE MEDICINE The science and the art of prolonging life, promoting & maintaining health, and preventing the occurrence of diseases. Applicable to the individual, family and the community. (each has its own strategies) What are its origins? Is this a specialty? What are its concerns?

Historical Accounts: Prevention Time Event Disease is considered a Wrath of God 1000 BC Health is a blessing : when sick, exorcisms were used Miasma Theory o Implicated “bad air”, polluted water, wastes & other environmental factors 1700s o but nobody knew about levels of CO2, sulfur, nitrous products, or other materials in the air yet. Germ Theory (brought by discovery of microscope, germs could be seen) 1800s o John Snow’s “epidemic investigation” o Microbes and vaccine era Shift of focus from communicable(germs, etc) to non-communicable diseases (personal factors such th 19 century as exposure to cigarettes, carcinogenic/ dangerous materials) Modern public health - focus on chronic diseases, th 20 century intervention programs(healthy diet, warning in cigarette packages about lung cancer, heart disease) Re-emerging diseases, new diseases AIDS, SARS, H1N1 “mosquitoes have become fiercer”:some bacteria st 21 century became resistant to medicine, higher generation medicines are needed; AIDS was unknown until the 80’s, still no cure; diseases easily spreads worldwide

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Outline V. Health A. Ecologic Concept B. Ecologic Concept Premises VI. Disease A. Models of Disease B. Natural History of Disease C. Determinants of Disease VII. Principles of Disease Prevention and Control

OBJECTIVES Define basic concepts and elements. Differentiate important features of community medicine from clinical practice. Explain the natural history of a disease process and its stages. Define the factors contributing to disease occurrence & the principles of its prevention and control. Explain the various concepts of disease causation.

II. EPIDEMIOLOGY Basic science in preventive medicine The study that deals with patterns of disease occurrence, injury, disabilities and their determinants among populations or groups of people. Quantitative, applied science, systematic & orderly methods. how it occurs; any type of health conditions uses scientific method: define problem, observe, generate hypothesis, testing to prove need to assess whether evidences are valid III. PUBLIC HEALTH “The art and science of preventing disease, prolonging life and promoting physical health and efficiency through organized community effort” & systematic social action. -C.A.Winslow A social movement for the promotion & protection of the community’s health. A. CONCERNS OF PUBLIC HEALTH Sanitation of the environment – basis is the 1700s belief of “bad air” Control of community infections Health, personal hygiene education

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Early diagnosis and treatment of diseases – to prevent the spread of disease to community Adequate standards of living – all for the maintenance of health -Charles Edward A. Winslow (1920)

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B. MODERN PUBLIC HEALTH Mission: “the fulfillment of society’s interest in assuring conditions in which people can be healthy.” Substance: “organized community efforts aimed at the prevention of disease and promotion of health” Organization framework: includes activities undertaken by the government and the private, voluntary organizations and individuals Core functions: Assessment of communities, Policy Development, Assurance of quality for health services “A coalition of profession united by their shared missions, their focus on disease prevention and health promotion, their approach - prospective in contrast to the reactive focus of therapeutic medicine, and their common science, epidemiology” –US Institute of Medicine, The Future of Public Health includes lifestyle healthcare should be cost efficient, high quality

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C. 10 ESSENTIAL PUBLIC HEALTH SERVICES Monitor health status Diagnose and investigate health problems, hazards(ex. Epidemics: don’t let it spread to other countries) 3. Inform, educate, empower people about health issues 4. Mobilize community partnerships 5. Develop policies and plans(ex. in airports, check if passenger has fever) 6. Enforce regulations that protect health and ensure safety 7. Assure provision of health care 8. Assure competent health care teams 9. Evaluate services: Efficiency, Acceptability, Quality (EAQ) 10. Research for new and innovative solutions to health problems 1. 2.

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IV. COMMUNITY MEDICINE Concepts, methods & approaches adopted from preventive medicine. Central to its approach is its concern for the social, cultural, environmental and biological features that influence the health of the community. Community Medicine Focus of Attention

Disease Approaches Employed

Interventions

Outcome

Community/groups of people (towns, barangays, et) Epidemiologic tools e.g. indices, rates and ratios(morbidity rates, mortality rates; frequency of occurrence of a disease); surveys Health program plans Prospective outlook seek out who’s sick to prevent spreading; maintaining health Evaluation studies, monitoring

Clinical Medicine Individual Patients

Medical History, PE, Laboratory exam

-Medical, surgical, palliative, treatment -“Reactive” outlook Follow up clinic visits

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A. ECOLOGIC CONCEPT Concerned with the total complex interrelationships among living organisms: the HOST, DISEASE AGENT & THE ENVIRONMENT.

B. ECOLOGIC CONCEPT PREMISES Interaction between the host and the disease agent Host & disease agents interaction is influenced by environmental factors  Equilibrium or balance among these three forces should be attained.  disease agent: can be biologic or nonbiologic  host should be in equilibrium/ balance with disease and environment Health results from the attainment of this equilibrium. Imbalance results to disease.  

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VI. DISEASE Imbalance between the forces found in the host, disease agent & the environment. “Failure of the adaptive mechanisms of an organism to counteract adequately the stimuli and stresses to which it is subject, resulting in disturbance in function or structure of any part, organ or system of the body”. -Blakiston’s New Gould Medical Dictionary can include physical, social, mental factors there is no one cause of disease, it’s always multifactorial

A. MODELS OF DISEASE 1. Multiple Causation or Multiactorial Etiology  The occurrence of disease is attributed to more than one factor: o Intrinsic factors – host factors influencing susceptibility o Extrinsic factors – biologic, social, physical factors in the environment that are relevant to health 2. Ecologic Models  Interrelations of: Host, Disease Agent & Environmental factors  Disease results from a potentially harmful change in any of the components of the system leading to disturbance of equilibrium. 3. Epidemiologic Triangle

Common Goal: HEALTHY individuals, families, and communities

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V. HEALTH Absence of disease, no impediments to an individual’s functioning or survival. “Soundness of body; that condition in which its functions are duly and efficiently charged” –Oxford English Dictionary “State of complete physical, mental & social well-being and not merely the absence of disease or infirmity.” –WHO all aspects of the human person: relationship with people in his environment, and the environment itself Group 3

**Each of these components must be analyzed for comprehension and prediction of disease patterns 4. Web of Causation  Disease never depends on a single isolated cause, but rather develops as a result of chains of causation – web. -MacMahon & colleagues (1960)

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5. Wheel Model of Man-Environment Interactions 2. 

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B. NATURAL HISTORYE OF DISEASE Disease process or life story of a disease (without intervention) starting from without or within the individual resulting in changes in body form and functions until recovery or death.  Stages 1. Pre-pathogenesis/Pre-disease: happens in the environment; Disease agent haven’t entered the host yet; interaction of host and disease agent, together with the relationship of host and environment  Host – Disease Agent – Environment Interaction 2. Pathogenesis: happens when balance is altered. Subclinical and clinical stages i. Subclinical stage/Latent Stage no apparent manifestations yet *Clinical Horizon: divides apparent from inapparent stage of disease ii. Prodrome: nonspecific manifestations iii. Frank Illness: when organism has entered the indicative organ e.g. in hepatitis – liver iv. Chronic/Complicated Stage 3. Outcome i. Recovery ii. Disability iii. Death 

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C. DETERMINANTS OF DISEASE HOST Factors o Age, gender, race, ethnic group, occupation, education, marital status, family history, socioeconomic group AGENT Factors o Infectious agents: virulence, infectivity, mode of transmission, immunogenicity o Physical, chemical, nutrient ENVIRONMENTAL Factors o Socio-cultural factors, physical & biologic environment : fauna & flora D. INTERVENTIONS: applied at various stages Primary Prevention: during Pre-pathogenesis stage Objective: o To prevent the initiation or onset of diseases. Maintain health – healthy practices, lifestyle, and habits = Primordial prevention (keeping person healthy, keeping environment clean, maintaining equilibrium) Various measures aimed at: o Promotion of general health & well being o Maintenance of healthy practices o Intercepting factors before they involve the human host directly General Health Promotive Measures: o Health education o Proper nutrition o Healthful habits, personality development o Adequate housing & environment o Personal hygiene Specific Protective Measures: o Prophylaxis: Immunization and chemograph o Isolation & quarantine o Water, food, milk sanitation o Proper waste disposal

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Vector & vermin control Risk factor control & prevention

Secondary Prevention: applied during Pathogenesis stage Objectives: o To recognize the disease process at its earliest stage to prevent its dissemination to other hosts. o To start treatment early in order to prevent disease progression and its sequelae or prolonged disability. o To prevent its dissemination to other host Early diagnosis and prompt treatment o Case finding o Surveillance of contacts o Medical, surgical & other interventions o Adequate care for the sick Disability limitation – institution of continued care & treatment in order to prevent further progression, complications and sequelae of the disease Tertiary Prevention: apply during Outcome stage Objectives: o Application of rehabilitative measures in order to maximize the use of the remaining functions. o To pave the way for the individual’s return to a useful place in society. Measures: Rehabilitation o Physical rehabilitation o Psychosocial rehabilitation o Occupational rehabilitation VII. PRINCIPLES OF DISEASE PREVENTION & CONTROL

SCHEMA

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Increase host resistance Avoidance of exposure Eliminate disease agent Modify environment: o unsuitable for biologic disease agents’ existence o Interrupt transmission of disease agents from a source to susceptible hosts o Allow healthful living of hosts

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