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History of Epidemiology

1. Epidemiology has very old origins and is linked to early human curiosity about disease.
2. It is said to have begun with Adam and Eve investigating the effects of the forbidden fruit.
3. The word epidemic is derived from Greek words epi meaning among, demos meaning people, and logos meaning study.
4. The term epidemic was used as early as the 3rd century B.C.
5. The foundation of modern epidemiology was laid in the 19th century.
6. Many classic epidemiological studies during this period helped in saving human lives.
7. In the 1850s, the Epidemiological Society of London was formed under Earl of Shaftesbury.
8. Early epidemiology mainly focused on infectious diseases.
9. Growth of bacteriology temporarily slowed epidemiology in universities.
10. In recent decades, epidemiology has grown rapidly with many modern off-shoots.

Common Components of Epidemiology

1. Most definitions of epidemiology contain three common components.
2. The first component is disease frequency.
3. Disease frequency deals with measurement of incidence and prevalence.
4. The second component is distribution of disease.
5. Distribution is studied according to time, place, and person.
6. It helps in identifying patterns of disease in populations.
7. The third component is determinants of disease.
8. Determinants include causes and risk factors of disease.
9. These components together help in understanding disease occurrence.
10. They form the core scientific basis of epidemiology.

Aims of Epidemiology as per IEA

1. The International Epidemiological Association has defined three main aims.
2. The first aim is to describe the distribution and magnitude of disease.
3. It helps to understand the extent of health problems in populations.
4. The second aim is to identify aetiological or risk factors of disease.
5. This helps in understanding disease causation.
6. The third aim is to provide data for planning health services.
7. It supports implementation and evaluation of health programmes.
8. Epidemiology helps in setting priorities among health services.
9. These aims are achieved through systematic studies.
10. The ultimate aim is prevention and control of disease.

Disease Frequency in Epidemiology

1. Measurement of disease frequency is a basic function of epidemiology.
2. It includes measurement of disease, disability, and death.
3. Frequency is usually expressed as rates or ratios.
4. Common measures include incidence rate and prevalence rate.
5. Disease frequency allows comparison between populations.
6. It helps in identifying suspected causal factors.
7. It provides clues to disease aetiology.
8. Measurement is also applied to health-related events.
9. Variables like blood pressure and cholesterol are included.
10. It makes epidemiology a quantitative science.

Distribution of Disease

1. Disease is not uniformly distributed in populations.
2. Distribution of disease follows definite patterns.
3. These patterns vary according to time, place, and person.
4. Time distribution shows trends and seasonal variations.
5. Place distribution shows geographical clustering of disease.
6. Person distribution shows differences by age, sex, and occupation.
7. Study of distribution helps in generating hypotheses.
8. It suggests possible risk factors.
9. This approach is known as descriptive epidemiology.
10. It helps in planning preventive measures.

Determinants of Disease

1. Determinants are factors responsible for disease occurrence.
2. They include biological, environmental, and social factors.
3. Study of determinants helps in identifying causes of disease.
4. It involves testing of aetiological hypotheses.
5. This is the real substance of epidemiology.
6. It uses epidemiological methods and principles.
7. It is known as analytical epidemiology.
8. Determinants help in understanding chronic diseases.
9. Examples include smoking and lung cancer.
10. It helps in planning effective prevention strategies.

Basic Measurements in Epidemiology

1. Epidemiology involves measurement of various health events.
2. Mortality measurement is an important component.
3. Morbidity measurement reflects disease burden.
4. Disability measurement shows impact of disease.
5. Natality measurement reflects population growth.
6. Environmental factors are also measured.
7. Health service utilization is studied.
8. Demographic variables are included.
9. Measurements must be accurate and reliable.
10. Valid measurements are essential for good conclusions.

Difference Between Epidemiology and Clinical Medicine

1. Epidemiology studies populations, while clinical medicine studies individuals.
2. Unit of study in epidemiology is population at risk.
3. Unit of study in clinical medicine is a patient.
4. Epidemiology focuses on prevention and control.
5. Clinical medicine focuses on diagnosis and treatment.
6. Epidemiologists go to the community to find cases.
7. Clinicians wait for patients to come to hospital.
8. Epidemiology uses rates and statistics.
9. Clinical medicine uses laboratory and clinical findings.
10. Both disciplines are complementary to each other.

##Epidemiological Approach

1. Epidemiological approach is a method of studying health problems.
2. It is based on asking questions and making comparisons.
3. Asking questions helps to understand disease occurrence.
4. Questions relate to time, place, and person.
5. Comparisons are made between affected and non-affected groups.
6. Differences give clues to disease causation.
7. This approach helps in identifying risk factors.
8. It guides planning of health programmes.
9. It is systematic and scientific.
10. It is essential for public health action.

Incidence and Prevalence

1. Incidence refers to new cases of disease.
2. It occurs in a defined population.
3. It is measured over a specific time period.
4. It indicates speed of disease occurrence.
5. Prevalence refers to total cases of disease.
6. It includes old and new cases.
7. It is measured at a particular time.
8. It shows burden of disease.
9. Incidence is useful for research.
10. Prevalence is useful for health planning.

Natural History of Disease

1. It is the course of disease without treatment.
2. Disease starts before symptoms appear.
3. First stage is stage of susceptibility.
4. Risk factors are present in this stage.
5. Second stage is subclinical stage.
6. Disease is present but no symptoms.
7. Third stage is clinical stage.
8. Signs and symptoms appear.
9. Diagnosis is possible.
10. Outcome may be recovery, disability, or death.

Iceberg Phenomenon of Disease

1. Iceberg phenomenon shows hidden disease burden.
2. Only few cases are visible.
3. Visible part shows diagnosed cases.
4. Hidden part shows undiagnosed cases.
5. Subclinical cases are large in number.
6. Carrier cases remain unnoticed.
7. Seen in chronic diseases.
8. Seen in diabetes and hypertension.
9. Seen in tuberculosis.
10. It highlights need for screening.

Modes of Transmission of Disease

1. Disease spreads from source to host.
2. Transmission may be direct.
3. Direct contact includes touching.
4. Droplet spread occurs by coughing.
5. Vertical transmission is mother to child.
6. Indirect transmission uses vehicles.
7. Food and water act as vehicles.
8. Vectors transmit disease through insects.
9. Airborne spread occurs through air.
10. Breaking transmission prevents disease.

Levels of Prevention

1. Prevention means avoiding disease.
2. Primordial prevention prevents risk factors.
3. It promotes healthy lifestyle.
4. Primary prevention acts before disease.
5. It includes health promotion.
6. It includes immunization.
7. Secondary prevention detects early disease.
8. Screening is part of secondary prevention.
9. Tertiary prevention limits disability.
10. Rehabilitation is included.

Host Factors in Epidemiology

1. Host refers to human being.
2. Age influences disease occurrence.
3. Sex affects disease pattern.
4. Genetic factors affect susceptibility.
5. Immunity provides resistance.
6. Nutrition influences health.
7. Occupation causes exposure.
8. Habits like smoking affect health.
9. Personal hygiene affects disease.
10. Host factors affect severity of disease.

Agent Factors in Disease Causation

1. Agent is a cause of disease.
2. Biological agents include bacteria.
3. Viruses cause viral diseases.
4. Parasites cause infestations.
5. Chemical agents include poisons.
6. Physical agents include heat and cold.
7. Mechanical agents cause injury.
8. Nutritional deficiency causes disease.
9. Excess nutrition causes disease.
10. Agent properties affect spread.

Environmental Factors Affecting Health

1. Environment affects health status.
2. Physical environment includes air.
3. Water quality affects health.
4. Housing affects disease spread.
5. Climate influences disease pattern.
6. Biological environment includes insects.
7. Animals act as reservoirs.
8. Social environment affects behavior.
9. Poverty affects health.
10. Clean environment promotes health.

Surveillance

1. Surveillance is continuous data collection.
2. It includes analysis of health data.
3. It helps in early disease detection.
4. It helps in outbreak control.
5. Passive surveillance uses routine reports.
6. Active surveillance searches cases.
7. Sentinel surveillance uses selected centers.
8. It guides health planning.
9. It evaluates health programs.
10. It supports disease control.

Screening

1. Screening detects disease early.
2. It is done among healthy people.
3. Simple tests are used.
4. Disease should be common.
5. Test should be safe.
6. Test should be acceptable.
7. Early treatment should exist.
8. It reduces complications.
9. It reduces mortality.
10. It improves prognosis.

Primary Health Care

1. Primary health care is basic health care.
2. It is essential health care.
3. It is universally accessible.
4. Community participation is important.
5. It is affordable to people.
6. It is first contact care.
7. It focuses on prevention.
8. It focuses on promotion.
9. It provides basic treatment.
10. It improves community health.

Components of Primary Health Care

1. Health education is included.
2. Nutrition promotion is provided.
3. Safe water supply is ensured.
4. Basic sanitation is important.
5. Maternal health care is given.
6. Child health care is provided.
7. Immunization is included.
8. Endemic disease control is done.
9. Treatment of common diseases is given.
10. Essential drugs are provided.

Health Indicators

1. Health indicators measure health status.
2. They are measurable variables.
3. They compare populations.
4. They assess health services.
5. Mortality indicators are included.
6. Morbidity indicators are included.
7. Life expectancy is an indicator.
8. IMR shows child health.
9. MMR shows maternal health.
10. They guide health planning.

Mortality Indicators

1. Mortality indicators measure deaths.
2. They reflect health status.
3. Crude death rate is basic.
4. Infant mortality rate is important.
5. Maternal mortality rate is used.
6. Under five mortality rate is used.
7. Neonatal mortality is included.
8. They help compare areas.
9. They evaluate programs.
10. They guide policy making.

Morbidity Indicators

1. Morbidity indicators measure illness.
2. They show disease burden.
3. Incidence rate is used.
4. Prevalence rate is used.
5. Notification rate is used.
6. OPD attendance reflects illness.
7. Hospital admission rate is used.
8. They help in planning services.
9. They assess community health.
10. They guide prevention.

Social Security Measures in India

1. Social security provides protection.
2. It gives economic support.
3. It helps during sickness.
4. It helps during disability.
5. Employee State Insurance is provided.
6. Provident fund ensures security.
7. Pension supports old age.
8. Maternity benefits help mothers.
9. Health insurance reduces expenses.
10. It improves social welfare.

Disability Limitation

1. Disability limitation is tertiary prevention.
2. It prevents complications.
3. It reduces disease severity.
4. Early treatment is important.
5. Physiotherapy is used.
6. Assistive devices are provided.
7. Regular follow-up is needed.
8. It prevents permanent disability.
9. It improves functional ability.
10. It improves quality of life.

Rehabilitation

1. Rehabilitation restores function.
2. It helps disabled persons.
3. It increases independence.
4. Medical rehabilitation treats physical problems.
5. Social rehabilitation helps adjustment.
6. Vocational rehabilitation provides work.
7. Psychological support is important.
8. Family support is needed.
9. Community support is essential.
10. It improves well-being.

Concept of Health and Disease

1. Health is complete well-being.
2. It includes physical health.
3. It includes mental health.
4. It includes social health.
5. Health is a dynamic state.
6. Disease is deviation from normal.
7. Disease affects body function.
8. Disease causes discomfort.
9. Disease may cause disability.
10. Health and disease are related.

10M | 20M

EPIDEMIOLOGICAL TRIAD

INTRODUCTION • Disease does not occur due to a single cause • It is the result of interaction between multiple factors • Epidemiology explains disease occurrence using a triad concept • This concept is known as epidemiological triad • It is the foundation of epidemiology and preventive medicine • It helps in understanding disease causation • It helps in planning prevention and control measures • Widely used in public health practice • Applicable to communicable and non-communicable diseases • Useful for outbreak investigation

DEFINITION • Epidemiological triad is a model explaining disease causation • It consists of three components – Host – Agent – Environment • Disease occurs when there is imbalance between these three • Control of disease is possible by modifying any one component

COMPONENTS OF EPIDEMIOLOGICAL TRIAD

1. HOST FACTORS

Definition • Host is the human being or living organism • Host provides environment for agent to survive and multiply • Host factors influence susceptibility and resistance

Important Host Factors

Age • Disease pattern varies with age • Childhood diseases include measles and diarrhoea • Adult diseases include hypertension and diabetes • Old age has reduced immunity

Sex • Some diseases are sex specific • Cervical cancer occurs in females • Prostate diseases occur in males • Hormonal differences influence disease

Genetic Factors • Genetic makeup affects susceptibility • Hereditary diseases run in families • Examples include sickle cell anaemia • Congenital disorders depend on genes

Immunity • Natural immunity provides resistance • Acquired immunity develops after infection or vaccination • Low immunity increases infection risk • Immunodeficiency increases severity

Nutrition • Good nutrition improves resistance • Malnutrition increases susceptibility • Protein energy malnutrition causes infections • Vitamin deficiency causes specific diseases

Occupation • Certain occupations increase exposure • Miners develop silicosis • Health workers exposed to infections • Factory workers exposed to noise and chemicals

Habits and Lifestyle • Smoking causes lung cancer • Alcohol causes liver disease • Sedentary lifestyle causes obesity • Poor hygiene increases infections

Socio-economic Status • Poverty increases disease risk • Poor housing causes overcrowding • Low education affects health awareness

2. AGENT FACTORS

Definition • Agent is any factor whose presence causes disease • Disease may or may not occur in absence of agent

Types of Agents

Biological Agents • Bacteria cause tuberculosis • Viruses cause measles and influenza • Parasites cause malaria • Fungi cause skin infections

Chemical Agents • Poisons cause toxicity • Pesticides cause health hazards • Air pollutants cause respiratory diseases • Excess fluoride causes fluorosis

Physical Agents • Heat causes heat stroke • Cold causes frostbite • Radiation causes cancer • Noise causes hearing loss

Mechanical Agents • Trauma causes injuries • Road accidents cause fractures • Occupational injuries are common

Nutritional Agents • Deficiency causes diseases • Vitamin A deficiency causes night blindness • Iodine deficiency causes goitre • Excess nutrition causes obesity

Properties of Agents

Infectivity • Ability of agent to enter host

Pathogenicity • Ability to cause disease

Virulence • Severity of disease produced

Toxicity • Ability to produce toxins

Antigenicity • Ability to stimulate immune response

3. ENVIRONMENTAL FACTORS

Definition • Environment includes all external conditions • It affects survival of agent and resistance of host • Plays a major role in disease transmission

Types of Environmental Factors

Physical Environment • Air quality affects respiratory health • Water contamination causes diarrhoea • Housing overcrowding increases infection • Climate affects disease distribution

Biological Environment • Insects act as vectors • Mosquito spreads malaria • Animals act as reservoirs • Rodents spread plague

Social Environment • Customs and traditions affect health • Cultural practices influence diet • Family structure affects health care • Literacy affects health awareness

Economic Environment • Poverty limits access to health care • Unemployment affects mental health • Low income leads to malnutrition

ROLE OF EPIDEMIOLOGICAL TRIAD IN DISEASE PREVENTION

Control of Host • Health education • Improving nutrition • Immunization • Lifestyle modification

Control of Agent • Early diagnosis and treatment • Chemoprophylaxis • Disinfection and sterilization • Vaccination

Control of Environment • Safe water supply • Sanitation • Vector control • Improved housing

DIAGRAM (TO BE DRAWN IN EXAM)

• Triangle diagram • Host at one corner • Agent at second corner • Environment at third corner • Disease written in center

IMPORTANCE OF EPIDEMIOLOGICAL TRIAD

• Helps understand disease causation • Useful in outbreak investigation • Guides preventive strategies • Helps in public health planning • Essential for control of communicable diseases • Also applicable to non-communicable diseases

LIMITATIONS

• Does not explain social determinants fully • Complex diseases need multifactorial models • Still basic and fundamental concept

CONCLUSION

• Disease is result of interaction of host, agent, and environment • Balance between three maintains health • Disturbance leads to disease • Control of any one factor prevents disease • Epidemiological triad is cornerstone of epidemiology

NATURAL HISTORY OF DISEASE WITH LEVELS OF PREVENTION

INTRODUCTION • Disease does not appear suddenly • It develops gradually over a period of time • Natural history of disease explains this progression • It describes events from beginning to final outcome • It is studied in absence of medical intervention • Helps in understanding when to apply prevention • Forms basis of preventive medicine • Applicable to communicable and non-communicable diseases • Essential for planning health programs • Guides public health strategies

DEFINITION • Natural history of disease is the course of disease • It occurs from initial interaction of agent and host • Progresses through different stages • Continues until recovery, disability, or death • Occurs without treatment or intervention

STAGES OF NATURAL HISTORY OF DISEASE

The natural history is divided into two main phases

1. Pre-pathogenesis phase
2. Pathogenesis phase

––––––––––––––––––––––––––––––– PRE-PATHOGENESIS PHASE –––––––––––––––––––––––––––––––

Definition • Disease has not yet started • Host, agent, and environment interact • Host is vulnerable but no disease present • No pathological changes seen • Individual appears healthy

Characteristics • Risk factors are active • Agent is present in environment • Host susceptibility exists • Environment favors disease development • This stage offers best opportunity for prevention

Examples • Smoking before lung cancer • High fat diet before heart disease • Mosquito breeding before malaria • Poor sanitation before diarrhoeal diseases

LEVEL OF PREVENTION IN PRE-PATHOGENESIS PHASE

1. PRIMORDIAL PREVENTION

Definition • Prevention of emergence of risk factors • Applied before risk factors appear

Measures • Health education • Promotion of healthy lifestyle • Avoidance of smoking and alcohol • Promotion of physical activity • Healthy dietary habits

Importance • Prevents lifestyle diseases • Most effective and economical • Focuses on population approach

2. PRIMARY PREVENTION

Definition • Prevention of disease occurrence • Applied before disease develops

Components

a. Health Promotion • Health education • Nutrition improvement • Environmental sanitation • Personal hygiene • Mental health promotion

b. Specific Protection • Immunization • Chemoprophylaxis • Use of protective devices • Safe water supply • Food safety measures

Examples • Vaccination against measles • Iodized salt to prevent goitre • Condoms to prevent HIV • Helmet use to prevent head injury

––––––––––––––––––––––––––––––– PATHOGENESIS PHASE –––––––––––––––––––––––––––––––

Definition • Disease process has started • Pathological changes occur • Host is affected by agent

Subdivisions

1. Subclinical stage
2. Clinical stage
3. Outcome stage

––––––––––––––––––––––––––––––– SUBCLINICAL STAGE –––––––––––––––––––––––––––––––

Characteristics • Disease present but no symptoms • Individual appears healthy • Pathological changes detectable • Early disease stage • Duration varies with disease

Examples • Incubation period in infectious diseases • Latent period in chronic diseases • Asymptomatic hypertension • Early diabetes without symptoms

LEVEL OF PREVENTION IN SUBCLINICAL STAGE

SECONDARY PREVENTION

Definition • Early detection and prompt treatment • Applied before symptoms appear

Components • Screening • Early diagnosis • Adequate treatment

Methods • Screening tests • Periodic medical examination • Case finding

Examples • Blood pressure screening • Blood sugar testing • Pap smear for cervical cancer • Chest X-ray for tuberculosis

Importance • Prevents progression of disease • Reduces complications • Improves prognosis • Reduces disease burden

––––––––––––––––––––––––––––––– CLINICAL STAGE –––––––––––––––––––––––––––––––

Characteristics • Signs and symptoms appear • Disease is clinically evident • Diagnosis can be made • Patient seeks medical care • Disease severity increases

Examples • Fever in malaria • Cough in tuberculosis • Chest pain in heart disease • Paralysis in stroke

LEVEL OF PREVENTION IN CLINICAL STAGE

TERTIARY PREVENTION

Definition • Prevention of disability • Limitation of complications • Restoration of function

Components

1. Disability limitation
2. Rehabilitation

Disability Limitation • Early and adequate treatment • Prevention of complications • Physiotherapy • Use of assistive devices

Rehabilitation • Medical rehabilitation • Social rehabilitation • Vocational rehabilitation • Psychological rehabilitation

Examples • Physiotherapy after stroke • Artificial limbs for amputees • Vocational training for disabled • Counseling for mental illness

––––––––––––––––––––––––––––––– OUTCOME STAGE –––––––––––––––––––––––––––––––

Possible Outcomes • Complete recovery • Partial recovery • Residual disability • Chronic disease • Death

Factors Affecting Outcome • Severity of disease • Host resistance • Timely treatment • Availability of health care

IMPORTANCE OF NATURAL HISTORY OF DISEASE

• Helps understand disease progression • Guides application of prevention • Helps in planning health services • Useful in epidemiological studies • Basis of preventive medicine • Reduces morbidity and mortality

SUMMARY

• Natural history explains disease development • Pre-pathogenesis phase is ideal for prevention • Primary prevention prevents disease occurrence • Secondary prevention detects disease early • Tertiary prevention reduces disability • Proper application improves public health outcomes

CONCLUSION • Disease develops through predictable stages • Prevention is possible at every stage • Understanding natural history is essential • Early prevention saves lives and resources • Core concept of community medicine

SCREENING OF DISEASE – PRINCIPLES, TYPES, AND USES

INTRODUCTION • Many diseases remain undetected in early stages • Symptoms appear only after disease progresses • Early detection helps in better treatment and prognosis • Screening is an important preventive strategy • It is a part of secondary prevention • Applied at community level • Helps reduce morbidity and mortality • Widely used in public health programs • Important tool in epidemiology • Applicable to both communicable and non-communicable diseases

DEFINITION • Screening is the presumptive identification of unrecognized disease • It is done by applying tests or examinations • It is done in apparently healthy individuals • It is not a diagnostic procedure • It separates apparently healthy from suspected cases • Suspected cases are referred for confirmation • It aims at early detection • It improves outcome of disease • It reduces complications • It is cost-effective in public health

OBJECTIVES OF SCREENING • To detect disease at early stage • To initiate early treatment • To prevent progression of disease • To reduce complications • To reduce disability • To reduce mortality • To improve quality of life • To identify high-risk individuals • To plan health services • To reduce disease burden in community

PRINCIPLES OF SCREENING

Disease-related principles • Disease should be an important health problem • Disease should have recognizable early stage • Natural history of disease should be well understood • There should be effective treatment available • Early treatment should be better than late treatment

Test-related principles • Screening test should be simple • Test should be safe and harmless • Test should be acceptable to population • Test should be reliable and valid • Test should be cost-effective • Test should have good sensitivity and specificity

Program-related principles • Adequate facilities for diagnosis and treatment • Clear policy on whom to treat • Screening should be continuous • Benefits should outweigh risks • Program should be socially acceptable

TYPES OF SCREENING

1. MASS SCREENING • Screening of entire population • Applied irrespective of risk status • Used when disease is common • Requires large resources • Example: Blood pressure screening camps • Example: Vision screening in schools • Advantage – covers large population • Disadvantage – costly and resource intensive

2. SELECTIVE SCREENING • Screening of high-risk groups only • More cost-effective • More efficient than mass screening • Focuses on vulnerable population • Example: TB screening in contacts • Example: Diabetes screening in obese adults • Preferred method in public health

3. MULTIPHASIC SCREENING • Multiple tests done at same time • Detects more than one disease • Saves time and manpower • Useful in health check-ups • Example: Blood sugar, BP, BMI together • Used in urban health programs

4. OPPORTUNISTIC SCREENING • Screening done when patient visits health facility • Not planned screening • Conducted during routine consultation • Example: BP measurement in OPD • Cost-effective and practical • Common in primary health care

SCREENING TEST CHARACTERISTICS

Sensitivity • Ability of test to identify true positives • High sensitivity reduces false negatives • Important for serious diseases

Specificity • Ability of test to identify true negatives • High specificity reduces false positives • Important to avoid unnecessary treatment

Validity • Accuracy of screening test • Depends on sensitivity and specificity • Valid test gives correct results

Reliability • Reproducibility of test results • Same result on repeated testing • Important for consistency

Predictive Value • Positive predictive value shows true disease • Depends on disease prevalence • Higher prevalence increases predictive value

USES OF SCREENING

Individual level • Early detection of disease • Early initiation of treatment • Better prognosis • Reduced complications • Reduced disability

Community level • Reduces disease burden • Reduces mortality rate • Helps in disease control • Improves quality of life • Promotes health awareness

Health system level • Helps in planning health services • Identifies high-risk groups • Supports preventive programs • Reduces treatment cost • Improves efficiency of health system

LIMITATIONS OF SCREENING • False positive results cause anxiety • False negative results give false reassurance • Overdiagnosis possible • Requires follow-up facilities • Cost and manpower needed • Not useful for all diseases • Ethical issues may arise

EXAMPLES OF COMMON SCREENING PROGRAMS • Blood pressure screening for hypertension • Blood sugar screening for diabetes • Pap smear for cervical cancer • Mammography for breast cancer • Sputum examination for tuberculosis • HIV screening in antenatal women

ROLE OF SCREENING IN PREVENTION • Part of secondary prevention • Detects disease in subclinical stage • Prevents progression • Reduces complications • Complements primary prevention

IMPORTANCE IN PUBLIC HEALTH • Essential epidemiological tool • Improves population health • Cost-effective disease control strategy • Supports national health programs • Reduces morbidity and mortality

CONCLUSION • Screening is early detection strategy • Applied to apparently healthy people • Based on sound principles • Effective when properly implemented • Plays major role in disease control • Integral part of preventive medicine

SURVEILLANCE – OBJECTIVES, TYPES, AND USES

Definition • Surveillance is continuous and systematic collection of health data • It includes analysis, interpretation, and dissemination of data • It is essential for planning, implementation, and evaluation of public health programs • It helps in timely public health action

Objectives of Surveillance • To detect early occurrence of disease • To identify outbreaks at an early stage • To monitor disease trends over time • To estimate disease burden in community • To identify high-risk groups • To guide planning of health services • To plan preventive and control measures • To evaluate effectiveness of health programs • To support health policy and decision making • To reduce morbidity and mortality

Types of Surveillance

Passive Surveillance • Routine reporting of diseases • Data collected from health facilities • No active search for cases • Less costly and simple • Under-reporting is common • Example: routine notification of diseases

Active Surveillance • Health workers actively search for cases • Regular visits to community and hospitals • More accurate data • Useful during outbreaks • More costly and time consuming • Used in eradication programs

Sentinel Surveillance • Selected institutions report data • Focus on specific diseases • High quality data obtained • Not representative of whole population • Used for HIV, influenza, polio

Syndromic Surveillance • Based on symptoms rather than diagnosis • Early detection of outbreaks • Useful when lab confirmation delayed • Used in disaster situations

Laboratory Surveillance • Based on lab confirmed cases • Provides accurate diagnosis • Helps in monitoring disease strains • Useful for antimicrobial resistance

Uses of Surveillance • Early detection of epidemics • Control of outbreaks • Monitoring disease trends • Identification of emerging diseases • Planning health services • Allocation of resources • Evaluation of health programs • Monitoring progress of disease control programs • Support research activities • Strengthening public health system

Importance • Backbone of public health system • Essential for disease prevention and control • Helps in protecting community health

MEASURES OF DISEASE FREQUENCY – INCIDENCE AND PREVALENCE

Introduction • Disease frequency shows how often disease occurs in a population • It is a basic measurement in epidemiology • Helps in understanding disease burden • Helps in planning and evaluation of health services • Main measures are incidence and prevalence

Incidence

Definition • Incidence is the number of new cases of disease • Occurring in a defined population • During a specified period of time

Formula • Incidence = New cases during a given time / Population at risk × 1000

Types of Incidence • Cumulative incidence • Incidence rate

Characteristics of Incidence • Measures risk of developing disease • Reflects speed of spread of disease • Depends on duration of observation • Useful for studying etiology • Useful for research and prevention

Uses of Incidence • Identifies risk factors • Helps in studying causation of disease • Useful in evaluation of preventive programs • Useful in outbreak investigation • Important for acute diseases

Prevalence

Definition • Prevalence is total number of cases • Includes both old and new cases • Present in population at a given time

Formula • Prevalence = All cases / Total population × 1000

Types of Prevalence • Point prevalence • Period prevalence

Characteristics of Prevalence • Shows disease burden • Depends on incidence and duration • High in chronic diseases • Reflects existing load on health services

Uses of Prevalence • Planning health services • Estimating manpower and resources • Useful for chronic diseases • Useful in community diagnosis • Helps in health policy making

Relationship Between Incidence and Prevalence • Prevalence depends on incidence and duration • Long duration increases prevalence • Short duration decreases prevalence • Cure and death reduce prevalence

Difference Between Incidence and Prevalence

Incidence • Measures new cases • Reflects risk • Used for etiology • Used in research • Used for acute diseases

Prevalence • Measures total cases • Reflects burden • Used for planning • Used in administration • Used for chronic diseases

Importance in Public Health • Essential for disease control • Helps in priority setting • Guides prevention strategies • Supports health planning • Strengthens epidemiological studies

CONCEPT OF HEALTH – CHANGING CONCEPTS AND DIMENSIONS OF HEALTH

Introduction • Health is a fundamental human right • It is essential for individual and community development • Concept of health has changed over time • Earlier concept was narrow and disease-oriented • Modern concept is broad and positive

Definition of Health • Health is a state of complete physical, mental, and social well-being • Not merely absence of disease or infirmity • Given by World Health Organization • Emphasizes positive health • Applies to individuals and communities

Changing Concepts of Health

Biomedical Concept • Health means absence of disease • Focus only on physical aspect • Disease is caused by biological agents • Role of doctor is diagnosis and treatment • Ignores social and mental factors

Ecological Concept • Health is dynamic equilibrium between man and environment • Disease occurs due to maladjustment • Emphasizes environmental factors • Focus on prevention • Includes host, agent, and environment

Psychosocial Concept • Health includes social and psychological factors • Social stress affects health • Lifestyle influences disease • Mental health is important • Community factors play major role

Holistic Concept • Health includes physical, mental, social, spiritual well-being • Human being is a whole unit • Focus on total well-being • Promotes healthy lifestyle • Most accepted modern concept

Dimensions of Health

Physical Dimension • Proper functioning of body systems • Freedom from disease and disability • Good nutrition and fitness • Ability to work efficiently • Normal growth and development

Mental Dimension • Balanced emotions • Ability to cope with stress • Positive self-esteem • Clear thinking and judgment • Emotional stability

Social Dimension • Ability to form relationships • Social adjustment • Participation in community • Respect for social norms • Good interpersonal relations

Spiritual Dimension • Sense of purpose in life • Moral and ethical values • Inner peace • Faith and belief system • Harmony with self and society

Vocational Dimension • Satisfaction with work • Safe working environment • Economic security • Skill utilization • Work-life balance

Positive Health • Not just absence of disease • Ability to lead socially and economically productive life • Physical fitness • Mental well-being • Social efficiency

Health–Disease Continuum • Health and disease are not separate entities • Individual moves on a scale • From positive health to death • Disease is deviation from normal • Health status changes over time

Importance of Health Concept • Helps in health planning • Guides preventive strategies • Promotes holistic care • Improves quality of life • Essential for public health practice

LEVELS OF PREVENTION WITH EXAMPLES

Introduction • Prevention means actions taken to stop disease • Aim is to reduce occurrence, severity, and complications • Prevention is better than cure • Levels of prevention are applied at different stages of disease • Concept given by Leavell and Clark

Definition • Levels of prevention are measures taken at different stages of disease • They prevent occurrence, progression, and consequences of disease • Includes primordial, primary, secondary, and tertiary prevention

Primordial Prevention • Prevention of emergence of risk factors • Applied before risk factors appear • Focuses on lifestyle and environmental changes • Mainly applied at population level • Very important for non-communicable diseases

Measures of Primordial Prevention • Promotion of healthy lifestyle • Prevention of smoking and alcohol habits • Healthy diet promotion • Physical activity promotion • Control of environmental pollution

Examples of Primordial Prevention • Health education in schools • Promotion of exercise among children • Ban on tobacco advertisements • Urban planning with parks • Encouraging healthy food habits

Primary Prevention • Applied before disease occurs • Aims to reduce incidence of disease • Acts during stage of susceptibility • Prevents disease occurrence • Includes health promotion and specific protection

Health Promotion • Improves general health of population • Encourages healthy lifestyle • Improves quality of life • Addresses social determinants of health • Empowers community

Measures of Health Promotion • Health education • Balanced diet • Personal hygiene • Environmental sanitation • Mental health promotion

Specific Protection • Protection against specific diseases • Reduces exposure to risk factors • Prevents particular diseases • More focused than health promotion • Based on scientific evidence

Measures of Specific Protection • Immunization • Chemoprophylaxis • Use of protective devices • Safe drinking water • Fortification of food

Examples of Primary Prevention • BCG vaccination for tuberculosis • Iodized salt to prevent goiter • Use of helmets to prevent head injury • Use of mosquito nets • Chlorination of water

Secondary Prevention • Applied after disease has started • Disease is in early stage • Aims to stop progression • Reduces duration and severity • Prevents complications

Components of Secondary Prevention • Early diagnosis • Prompt treatment • Screening of disease • Case finding • Referral services

Examples of Secondary Prevention • Screening for hypertension • Pap smear for cervical cancer • Blood sugar testing for diabetes • Chest X-ray for tuberculosis • Mammography for breast cancer

Tertiary Prevention • Applied when disease is established • Aims to reduce disability • Prevents complications • Restores function • Improves quality of life

Components of Tertiary Prevention • Disability limitation • Rehabilitation • Long-term care • Supportive therapy • Follow-up services

Disability Limitation • Prevents worsening of disease • Prevents deformity • Early and adequate treatment • Physiotherapy • Use of assistive devices

Rehabilitation • Restores physical, mental, and social function • Helps patient return to normal life • Includes medical, social, and vocational rehabilitation • Family and community support important • Improves self-reliance

Examples of Tertiary Prevention • Physiotherapy after stroke • Artificial limbs for amputees • Speech therapy • Occupational therapy • Vocational training

Importance of Levels of Prevention • Reduces disease burden • Saves cost of treatment • Improves life expectancy • Enhances quality of life • Essential for public health planning

HEALTH INDICATORS – TYPES AND IMPORTANCE

Introduction • Health indicators are tools to measure health status • They help to assess community health • Used for comparison between populations • Useful for planning and evaluation • Essential for public health decision making

Definition • Health indicators are measurable variables • They reflect health status of individuals or communities • Used to monitor changes over time • Used by health systems and governments • Recommended by :contentReference[oaicite:0]{index=0}

Need for Health Indicators • To measure health status • To identify health problems • To set priorities • To plan health services • To evaluate health programs

Characteristics of Ideal Health Indicator • Valid and reliable • Simple to measure • Sensitive to changes • Specific to health conditions • Comparable over time and place

Classification of Health Indicators

Mortality Indicators • Measure deaths in population • Reflect overall health status • Commonly used indicators • Easy to calculate • Widely accepted

Examples of Mortality Indicators • Crude death rate • Infant mortality rate • Neonatal mortality rate • Under-five mortality rate • Maternal mortality rate

Morbidity Indicators • Measure illness in population • Show disease burden • Reflect community sickness • Useful for planning services • Help in disease control

Examples of Morbidity Indicators • Incidence rate • Prevalence rate • Notification rate • OPD attendance • Hospital admission rate

Disability Indicators • Measure impact of disease • Reflect loss of function • Important for chronic diseases • Show long-term effects • Useful for rehabilitation planning

Examples of Disability Indicators • Disability-adjusted life years (DALY) • Sickness absenteeism • Days of restricted activity • Bed-disability days • Work-loss days

Nutritional Indicators • Reflect nutritional status • Important for children and mothers • Show malnutrition prevalence • Useful in food programs • Indicate poverty level

Examples of Nutritional Indicators • Weight for age • Height for age • Weight for height • Body mass index • Clinical signs of deficiency

Health Care Delivery Indicators • Measure health service availability • Reflect utilization of services • Indicate system efficiency • Useful for administration • Help in resource allocation

Examples of Health Care Indicators • Doctor-population ratio • Bed-population ratio • Immunization coverage • Institutional delivery rate • OPD attendance rate

Environmental Indicators • Measure environmental health • Reflect living conditions • Affect disease occurrence • Important for prevention • Linked to sanitation

Examples of Environmental Indicators • Safe water coverage • Sanitary latrine coverage • Housing conditions • Air quality levels • Waste disposal facilities

Socio-economic Indicators • Reflect social development • Influence health outcomes • Indicate inequality • Useful for planning • Related to lifestyle diseases

Examples of Socio-economic Indicators • Literacy rate • Per capita income • Poverty level • Employment rate • Housing index

Quality of Life Indicators • Measure well-being • Include subjective assessment • Reflect life satisfaction • Used in chronic disease • Patient-centered approach

Examples of Quality of Life Indicators • Physical functioning • Mental well-being • Social relationships • Life satisfaction score • Health-related quality of life

Uses of Health Indicators • Assess health status • Compare populations • Monitor trends • Plan health services • Evaluate health programs

Limitations of Health Indicators • Data may be incomplete • Under-reporting of diseases • Variation in definitions • Socio-cultural differences • Need proper interpretation

Conclusion • Health indicators are essential tools • They guide public health action • Help in rational planning • Improve health system performance • Essential for community health improvement

PRIMARY HEALTH CARE – PRINCIPLES AND ELEMENTS

Introduction • Primary health care is the foundation of health system • It focuses on basic health needs • It aims at universal health coverage • It emphasizes prevention and promotion • It was globally accepted after Alma-Ata declaration

Definition • Primary health care is essential health care • It is based on practical and scientific methods • It is socially acceptable to community • It is universally accessible • Defined by :contentReference[oaicite:0]{index=0}

Objectives of Primary Health Care • Achieve health for all • Reduce morbidity and mortality • Promote healthy living • Prevent diseases • Provide basic curative services

Features of Primary Health Care • First level of contact • Close to community • Continuous care • Comprehensive services • Community-oriented approach

Principles of Primary Health Care

Equitable Distribution • Health services available to all • Focus on rural and underserved areas • Reduce urban-rural gap • Equal access irrespective of income • Social justice in health care

Community Participation • Active involvement of people • Community identifies its own needs • People participate in planning • Increases acceptance of services • Improves sustainability

Intersectoral Coordination • Health depends on many sectors • Cooperation with education sector • Coordination with agriculture • Involvement of housing and sanitation • Multidisciplinary approach

Appropriate Technology • Technology suitable to local needs • Affordable and acceptable methods • Scientifically sound techniques • Easy to maintain • Culturally acceptable

Emphasis on Prevention • Focus on promotive care • Preventive services prioritized • Early detection of disease • Health education encouraged • Cost-effective approach

Elements of Primary Health Care

Health Education • Education about health problems • Promotion of healthy lifestyle • Prevention of diseases • Awareness about nutrition and hygiene • Community empowerment

Promotion of Food Supply and Nutrition • Adequate nutrition for all • Prevention of malnutrition • Focus on mothers and children • Nutrition supplementation programs • Food security measures

Safe Water Supply and Sanitation • Provision of clean drinking water • Prevention of water-borne diseases • Proper waste disposal • Improved sanitation facilities • Environmental hygiene

Maternal and Child Health Care • Antenatal care • Intranatal services • Postnatal care • Child growth monitoring • Family planning services

Immunization • Protection against communicable diseases • Universal immunization coverage • Cost-effective intervention • Reduces child mortality • Prevents outbreaks

Control of Endemic Diseases • Identification of local diseases • Vector control measures • Early diagnosis and treatment • Health education • Surveillance activities

Treatment of Common Diseases and Injuries • Basic curative services • First aid and emergency care • Management of minor illnesses • Referral services • Continuity of care

Provision of Essential Drugs • Availability of basic medicines • Rational use of drugs • Affordable prices • Standard treatment guidelines • Essential drug list followed

Role of Primary Health Care in India • Strengthens rural health system • Delivered through subcentres • Primary health centres • Community health centres • Backbone of public health services

Advantages of Primary Health Care • Cost-effective • Prevents diseases • Improves health indicators • Reduces hospital burden • Empowers community

Challenges in Primary Health Care • Inadequate manpower • Limited resources • Population growth • Awareness issues • Infrastructure problems

Conclusion • Primary health care is cornerstone of health system • It ensures universal access • Focuses on prevention and promotion • Encourages community participation • Essential for sustainable health development