Acculturation - Park's Textbook of Preventive and Social Medicine

Definition

• Park's Textbook of Preventive and Social Medicine, p. 769

Ways by Which Culture Contact (Acculturation) Takes Place

1. Trade and commerce
2. Industrialization
3. Propagation of religion
4. Education
5. Conquest

Examples Given in Park's

Context: Culture vs. Acculturation

"Culture is defined as learned behaviour which has been socially acquired."

Distinction from Socialization

Health Relevance (Park's Emphasis)

• Personal hygiene
• Nutrition
• Immunization
• Seeking early medical care
• Family planning
• Child rearing
• Disposal of refuse and excreta
• Outlook on health and disease

Epidemiology - Definition, Classification of Studies & DVT/OCP Example

PART 1: Definition of Epidemiology

Standard Definition (Park's):

"The study of the occurrence and distribution of health-related events, states, and processes in specified populations, including the study of the determinants influencing such processes, and the application of this knowledge to control relevant health problems."

1. Disease frequency - measurement via rates and ratios (incidence, prevalence, death rate)
2. Distribution - by time, place, and person
3. Determinants - geophysical, biological, behavioural, social, cultural, economic, and political factors that influence health

PART 2: Classification of Epidemiological Studies

EPIDEMIOLOGICAL STUDIES
├── 1. OBSERVATIONAL STUDIES
│   ├── A. Descriptive Studies
│   └── B. Analytical Studies
│       ├── (i)  Ecological / Correlational — population as unit of study
│       ├── (ii) Cross-sectional / Prevalence — individual as unit of study
│       ├── (iii) Case-Control / Case-reference — individual as unit of study
│       └── (iv) Cohort / Follow-up — individual as unit of study
│
└── 2. EXPERIMENTAL STUDIES (Intervention Studies)
    ├── a. Randomized Controlled Trials / Clinical Trials — patients as unit
    ├── b. Field Trials — healthy people as unit of study
    └── c. Community Trials / Community Intervention Studies — community as unit

Brief Description of Each Type:

"These studies cannot be regarded as watertight compartments; they complement one another." - Park

PART 3: Ascertaining the Role of Contraceptive Pills in Causation of DVT

Step 1: Formulate the Hypothesis

"Oral contraceptive pills (OCPs) are a risk factor for the causation of deep vein thrombosis (DVT) in females."

Step 2: Define Cases and Controls

• Cases: Females diagnosed with DVT (confirmed by Doppler ultrasound / venography), admitted in hospitals or identified from registries
• Controls: Females of similar age, sex (matched), without DVT - drawn from:
  • Hospital patients (non-DVT conditions)
  • Neighbourhood controls
  • General population (random sample)
• Controls must be matched for age, parity, socioeconomic status (known confounders)

Step 3: Selection Criteria

• Clearly define a "case" - what constitutes DVT (clinical + radiological criteria)
• Clearly define an "exposed person" - what constitutes OCP use (type, duration, dosage)
• Exclusion criteria: females with hereditary thrombophilia, immobility, malignancy (alternate causes of DVT)

Step 4: Data Collection (Exposure Assessment)

• Structured interview / questionnaire
• Medical records
• Information on: duration of use, type of pill, dose of estrogen

Step 5: Matching

• Age
• Parity
• Smoking status
• Obesity
• Family history of clotting disorders

Step 6: Analysis

(a) Test of Statistical Association

• Exposure rate in cases = a / (a+c)
• Exposure rate in controls = b / (b+d)

• If P ≤ 0.05 → statistically significant
• The smaller the P value, the greater the statistical significance

"Statistical association does not imply causation. Statement of P value is thus an inadequate, although common end-point." - Park

(b) Estimation of Risk - Odds Ratio (OR)

Odds Ratio (OR) = ad / bc

• OR = 1 → No association
• OR > 1 → Positive association (OCP use increases DVT risk)
• OR < 1 → Negative association (protective)

Step 7: Establishing Causation

1. Strength of association - High OR
2. Consistency - Repeated in different studies/populations
3. Specificity - OCP use linked specifically to DVT
4. Temporality - OCP use preceded DVT (exposure before disease)
5. Biological gradient - Higher dose/duration of OCP → higher DVT risk
6. Plausibility - Estrogen in OCPs increases clotting factors (biologically plausible)
7. Coherence - Consistent with lab/animal data
8. Experiment - Withdrawal of OCP reduces DVT incidence
9. Analogy - Similar associations known for other estrogen-related conditions

Summary Table: Case-Control Study for OCP-DVT

Sentinel Surveillance

Definition

"No routine notification system can identify all cases of infection or disease. A method for identifying the missing cases and thereby supplementing the notified cases is required. This is known as 'sentinel surveillance.'"

• Park's Textbook of Preventive and Social Medicine, p. (Epidemiological Surveillance chapter)

Why is it Needed?

• Under-reporting due to passive nature
• Reporting biases (many cases go undetected or unreported)
• Lack of detailed clinical or laboratory data

Key Features

Advantages

1. Reporting biases are minimized
2. Feed-back of information to providers is simplified
3. Provides more valuable and detailed information than traditional notification systems
4. Can be developed into a full notification system for more detailed information
5. Less costly than maintaining an ongoing notification system in some settings
6. Identifies missing/under-reported cases

Examples of Sentinel Surveillance in Park's

1. Malaria Sentinel Surveillance

• Severe malaria cases are not reported separately
• Only a small fraction of malaria deaths are recorded

• 1-3 sentinel sites in large hospitals per district (depending on size)
• Recording all OPD and IPD cases of malaria
• Recording malaria-related deaths

• Annual Parasite Incidence (API)
• Annual Blood Examination Rate (ABER)
• Annual Falciparum Incidence (AFI)
• Slide Positivity Rate (SPR)
• Slide Falciparum Rate (SFR)

2. HIV Sentinel Surveillance (India)

1. Determine the level of HIV infection among general population and high-risk groups in different states
2. Understand trends of HIV epidemic
3. Understand geographical spread and identify emerging pockets
4. Provide information for prioritization of programme resources and evaluation of programme impact
5. Estimate HIV prevalence and burden in the country

• Annual cross-sectional survey of risk groups, at the same place over a few years
• Unlinked anonymous serological testing (ERS - testing without name identification)
• Pregnant women attending antenatal clinics (ANC) are taken as a proxy for general population
• Inclusion of data from high-risk populations through targeted intervention sites
• Started in 1994 with 55 sentinel sites, expanded to 180 by 1998

3. Dengue / Acute Encephalitis Syndrome (AES/JE)

• Government of India identified 521 sentinel surveillance hospitals with laboratory support for augmented diagnostic facilities in endemic states
• 14 Apex Referral Laboratories identified for advanced diagnosis and backup support
• In sentinel surveillance network, AES/JE diagnosed by IgM Capture ELISA; virus isolation done at National reference laboratories

4. Integrated Disease Surveillance Programme (IDSP) - Sentinel Surveillance Component

• Sexually transmitted diseases / blood-borne: HIV, HBV, HCV
• Other conditions: Water quality monitoring, outdoor air quality monitoring (large urban centres)

Sentinel Surveillance vs. Routine Notification - Comparison

Emerging and Re-Emerging Infectious Diseases

Definition

Emerging Infectious Diseases

"Emerging infectious diseases are those whose incidence in humans has increased during the last two decades or which threaten to increase in the near future."

• Newly appearing infectious diseases (e.g., COVID-19, AIDS, Ebola)
• Diseases spreading to new geographical areas (e.g., cholera in South America, yellow fever in Kenya)

Re-Emerging Infectious Diseases

• Development of antimicrobial resistance
• Breakdown in public health measures
• Relaxation of immunization practices

Factors Responsible for Emergence and Re-emergence

• Changes in lifestyle and behaviour (drug use, increased sexual partners) - syphilis, HIV
• Practices of modern medicine - viral hepatitis spread via dialysis, blood transfusions
• Relaxation of immunization - diphtheria resurgence in former USSR
• New animal diseases and foodborne risks - BSE (mad cow disease) → variant CJD
• Drug treatments that do not result in cure - promote drug-resistant strains

Mode of Transmission

• Person-to-person spread
• Insect vectors (mosquitoes, ticks)
• Animal reservoirs (zoonoses)
• Contaminated water or food

Important Examples

A. Newly Emerging Diseases

• Most dramatic modern example
• First case: November 2019; declared pandemic by WHO: March 11, 2020
• Caused virtual global lockdown; social distancing and masking as primary control measures
• ~110 million cases with 2.45 million deaths by February 2021

• Virus unknown until 1983
• ~38 million people living with HIV globally (2019)
• 1.2 million new cases with 690,000 deaths in 2019
• Spread accelerated by international travel, sexual behaviour changes

• Member of family Filoviridae; 5 distinct species (Zaire, Reston, Sudan, Tai, Bundibugyo)
• First appeared in Zaire and Sudan in 1976
• Recent epidemic started December 2013 in Guinea; 25,515 cases, >10,000 deaths by April 2015
• Case fatality rate up to 70%
• Incubation period: 2-21 days (not infective during this period)
• Transmission: direct contact with blood/body fluids of infected animals (chimpanzees, gorillas, fruit bats) or symptomatic humans
• NOT transmitted via air, water, or food
• No specific treatment; no vaccine available

• Characterized by respiratory failure; CFR >50%
• First recognized in USA in 1993; spread to >20 states
• Carrier: rodents (deer mice)
• Other hantaviruses in Asia cause haemorrhagic fever with renal involvement

• First reported in 1982
• Causes serious diarrhoeal illness, sometimes leading to kidney failure
• Linked to undercooked hamburger beef and unpasteurized milk

• Completely new strain appeared in south-eastern India in 1992
• Spread to China, Thailand, and SE Asia

B. Re-Emerging Diseases

Global Distribution

• Red dots = Newly emerging diseases (e.g., COVID-19, Ebola, Zika, Hantavirus, SARS, MERS-CoV, Nipah)
• Blue dots = Re-emerging/resurging diseases (e.g., Measles, Cholera, Dengue, TB, Diphtheria, Plague)
• Black dot = "Deliberately emerging" (e.g., Anthrax bioterrorism)

Antimicrobial Resistance - A Special Category

• Treatments that do not result in cure
• Subtherapeutic doses of antibiotics
• Counterfeit drugs
• Increasing worldwide use of antimicrobials

Public Health Significance

"National health has become an international challenge. An outbreak anywhere must now be seen as a threat to virtually all countries, especially those that serve as major hubs of international travel." - Park's

• Park's Textbook of Preventive and Social Medicine - Chapter on International Health, pp. 405-407
• Sherris & Ryan's Medical Microbiology, 8th Edition - Chapter 5

Hazards of Urbanization

Definition of Urbanization

"Towns (places with municipal corporation, municipal area committee, town committee, notified area committee or cantonment board); also, all places having 5,000 or more inhabitants, a density of not less than 1,000 persons per square mile or 390 per square kilometre, pronounced urban characteristics and at least three-fourths of the adult male population employed in pursuits other than agriculture."

Causes of Urbanization (Rural-to-Urban Migration)

• Employment opportunities
• Attraction of better living conditions
• Availability of social services (education, health, transport, entertainment)

"The continuous migration of people from the countryside to urban areas in India constitutes a social crisis, the ramification of which may eventually impair the quality of life." - Park's

Health Hazards of Urbanization

1. Environmental Pollution

2. Creation of Slums

• Rapid and unplanned migration leads to growth of slums and shanty towns
• Slums are characterized by:
  • Extreme overcrowding
  • Lack of safe drinking water
  • Inadequate or absent sanitation
  • Poor housing and ventilation
  • Deficient refuse disposal
• Slum dwellers are among the most vulnerable populations for communicable disease
• NUHM (National Urban Health Mission) specifically targets slum dwellers and homeless, rag-pickers, street children, construction workers, sex workers, and temporary migrants

3. Overcrowding

• High population density in urban areas facilitates person-to-person spread of infectious diseases
• Promotes transmission of:
  • Respiratory infections (TB, influenza, COVID-19)
  • Meningitis
  • Childhood infections (measles, chickenpox)

4. Communicable Disease Problems

• Tuberculosis (TB) - overcrowding + poor ventilation = major risk
• Sexually transmitted infections (STIs) - associated with urban lifestyle changes and sex work
• Vector-borne diseases - urban water stagnation breeds mosquitoes (dengue, malaria)
• Waterborne diseases - contaminated urban water supplies

5. Accidents and Injuries

• Road traffic accidents - rapid increase in vehicles; a major urban hazard
• Industrial accidents - unsafe working conditions in urban factories
• Domestic accidents

6. Mental Health Problems

7. Social Problems

• Alcoholism
• Drug dependence
• Prostitution
• Gambling
• Crime

8. Non-communicable Diseases (NCDs)

• Sedentary lifestyle → obesity, diabetes, cardiovascular disease
• Dietary changes → increased consumption of processed food; nutritional disorders
• Tobacco use → lung cancer, COPD
• Hypertension - related to stress, noise, sedentary work

9. Inadequate Water Supply and Sanitation

• Urban growth outpaces infrastructure development
• Poor sewage disposal; open defecation in slums
• Inadequate refuse/solid waste management
• Stagnant water breeding grounds for vectors

10. Housing Problems

• Shortage of affordable housing
• Poor ventilation, inadequate natural light
• Overcrowded tenements; promotes spread of respiratory infections
• Lack of recreational spaces

11. Nutrition and Food Safety Issues

• Food adulteration common in urban markets
• Urban poor at risk of protein-energy malnutrition and micronutrient deficiencies
• Changes in food habits - unhealthy fast food consumption

Summary Table - Hazards of Urbanization

Public Health Response

1. Improving health status of urban slum dwellers and vulnerable populations
2. Public health thrust on sanitation, clean drinking water, vector control
3. Strengthening public health capacity of urban local bodies
4. Deploying ASHAs/Link Workers (1 per 1000-2500 urban poor) for outreach services

Epidemiological Study Designs, Time Trends & Case-Control vs Cohort Study

PART 1: Types of Epidemiological Study Designs

EPIDEMIOLOGICAL STUDIES
│
├── 1. OBSERVATIONAL STUDIES
│   ├── A. DESCRIPTIVE STUDIES
│   │       – Describe disease by Time, Place, Person
│   │       – Generate hypothesis
│   │
│   └── B. ANALYTICAL STUDIES (test hypothesis)
│           ├── (i)  Ecological / Correlational     → Population as unit
│           ├── (ii) Cross-sectional / Prevalence   → Individual as unit
│           ├── (iii) Case-Control / Retrospective  → Individual as unit
│           └── (iv) Cohort / Prospective / Follow-up → Individual as unit
│
└── 2. EXPERIMENTAL STUDIES (Intervention Studies)
    ├── a. Randomized Controlled Trials (RCTs) / Clinical Trials → Patients
    ├── b. Field Trials                                          → Healthy people
    └── c. Community Trials / Community Intervention Studies    → Communities

"These studies cannot be regarded as watertight compartments; they complement one another." - Park's

PART 2: Types of Time Trends in Disease Occurrence

I. Short-term Fluctuations (Epidemics)

"The occurrence in a community or region of cases of an illness or other health-related events clearly in excess of normal expectancy."

Types of Epidemics:

• Exposure is brief and essentially simultaneous
• All cases develop within one incubation period
• Epidemic curve rises and falls rapidly, with no secondary waves
• Explosive clustering of cases within a narrow time interval
• Example: Food poisoning outbreak at a wedding banquet; Bhopal gas tragedy; Minamata disease (methyl mercury-contaminated fish in Japan)

• Exposure from the same source is prolonged, repeated, or intermittent
• Epidemic curve is more extended and irregular
• Example: Legionnaire's disease (Philadelphia, 1976) - common-source, continuous exposure; gonorrhoea outbreak from a common source (prostitute)

• Results from person-to-person transmission
• Gradual rise, tails off over a much longer period
• Continues until susceptibles are depleted or no longer exposed
• Speed depends on herd immunity, opportunities for contact, secondary attack rate
• Sub-types:
  • (a) Person-to-person: hepatitis A, polio
  • (b) Arthropod vector: malaria, dengue
  • (c) Animal reservoir: rabies, plague

• Gradual build-up over many years
• Example: HIV/AIDS epidemic; tobacco-related lung cancer epidemic

II. Periodic Fluctuations

• Regular variation linked to a specific season
• Related to temperature, humidity, rainfall, vector life cycles, overcrowding
• Examples:
  • Measles and varicella - peak in early spring
  • Upper respiratory infections - peak in winter months
  • Bacterial gastroenteritis - prominent in summer (fly multiplication)
  • Dengue/DHF in India - starts in July, peaks in September-November (late summer and monsoon)
  • Malaria - peaks in monsoon and post-monsoon season
  • Non-infectious: sunstroke (summer), hay fever (spring), snakebite (monsoon)

• Regular recurrence every few years
• Depends on accumulation of susceptibles in the population
• Examples:
  • Measles - used to show cyclic peaks every 2-3 years before vaccination
  • Influenza - shows periodic cycles
  • Meningococcal meningitis - shows cyclic periodicity

III. Long-term or Secular Trends

"The term 'secular trend' implies changes in the occurrence of disease (i.e., a progressive increase or decrease) over a long period of time, generally several years or decades."

• Coronary heart disease (CHD) - consistent upward trend in developed countries over the past 50 years
• Lung cancer - progressive increase, linked to smoking
• Diabetes mellitus - progressive increase worldwide
• Mental health disorders

• Tuberculosis - progressive decline with improved living standards and chemotherapy
• Typhoid fever - decline with improved water supply and sanitation
• Diphtheria - decline with immunization
• Poliomyelitis - decline with vaccination

Interpretation of Time Trends

• Identify which diseases are increasing or decreasing
• Identify emerging health problems
• Assess effectiveness of control measures
• Formulate aetiological hypotheses
• Determine whether changes are due to: changes in aetiological agent; changes in diagnosis/reporting; changes in age distribution; or changes in quality of life/socioeconomic status

PART 3: Differences Between Case-Control and Cohort Study

Key Differences Summary (Mnemonic):

Health Indicators

Definition

"Indicators are variables which help to measure changes." (WHO guidelines for health programme evaluation)

• To measure the health status of a community
• To compare health status of one country with another
• For assessment of health care needs
• For allocation of scarce resources
• For monitoring and evaluation of health services, activities, and programmes

• Health indicator - preferred for health trends (measures single variable)
• Health index - an amalgamation of multiple health indicators

Characteristics of Ideal Indicators (VRSSFR)

"But in real life there are few indicators that comply with all these criteria. Health, like happiness, cannot be defined in exact measurable terms."

Classification of Health Indicators

1. Mortality indicators
2. Morbidity indicators
3. Disability rates
4. Nutritional status indicators
5. Health care delivery indicators
6. Utilization rates
7. Indicators of social and mental health
8. Environmental indicators
9. Socio-economic indicators
10. Health policy indicators
11. Indicators of quality of life
12. Other indicators

1. Mortality Indicators

• Deaths per 1,000 population per year
• A "fair indicator" of comparative health
• Limitation: influenced by age-sex composition of population
• Decrease in death rate = good tool for assessing health improvement

• "The average number of years that will be lived by those born alive if current age-specific mortality rates persist"
• Positive health indicator - increase in life expectancy = improvement in health
• Good indicator of socio-economic development
• Life expectancy at age 1: excludes influence of infant mortality
• Life expectancy at age 5: excludes influence of child mortality

• Deaths under 1 year per 1,000 live births
• Sensitive indicator of the health status of a community
• Reflects the level of nutrition, hygiene, and availability of healthcare
• Often used as a proxy for overall community health
• Widely used for international comparisons

• Deaths in children under 5 years per 1,000 live births
• Reflects child health and survival; used as SDG indicator (SDG 3.2.1)

• Deaths of women due to pregnancy/childbirth per 100,000 live births
• SDG indicator (SDG 3.1.1)

• TB mortality rate, AIDS-related mortality, malaria mortality, NCD mortality

• Proportion of all deaths attributed to a specific cause
• Useful for describing the pattern of mortality in a population
• PMR > 50% for ages 50+ = "positive health indicator" (good health, most people dying in old age)

• Measures impact of disease on daily living

2. Morbidity Indicators

• Incidence and prevalence rates of specific diseases
• Notification rates (communicable diseases)
• Attendance rates at outpatient departments
• Admission rates / bed occupancy rates
• Sickness absence rates from work/school
• New cases of HIV, TB, malaria, STIs (SDG indicators)

3. Disability Rates

• Days of restricted activity
• Bed disability days
• Work-loss days
• Prevalence of blindness, deafness, mental retardation, physical disability

4. Nutritional Status Indicators

• Anthropometric measures: weight-for-age, height-for-age, weight-for-height in children
• Low birth weight (< 2.5 kg) percentage - reflects maternal nutrition
• Nutritional deficiency diseases: prevalence of anaemia, PEM, vitamin A deficiency, iodine deficiency

5. Health Care Delivery Indicators

• Doctor-population ratio (physician density per 10,000)
• Nurse-population ratio
• Hospital beds per 1,000 population
• Population per health facility
• Availability and accessibility of health services

6. Utilization Rates

• Percentage of infants fully immunized
• Percentage of deliveries conducted by trained personnel
• Antenatal care coverage
• Proportion of population using family planning methods
• Outpatient attendance per person per year

7. Indicators of Social and Mental Health

• Rates of mental disorders (depression, schizophrenia)
• Suicide rates (SDG 3.4.2)
• Homicide rates (SDG 16.1.1)
• Rates of road traffic accidents (SDG 3.6.1)
• Rates of crime, delinquency, drug abuse, alcohol consumption
• School drop-out rates

8. Environmental Indicators

• Proportion of population with access to safe drinking water
• Proportion with access to adequate sanitation
• Air quality - particulate matter levels, SO₂, NOx
• Water quality indices
• Solid waste disposal adequacy

9. Socio-Economic Indicators

• Per capita GNP/GDP
• Adult literacy rate (especially female literacy)
• Income distribution (Gini coefficient)
• Unemployment rate
• Food availability and nutritional adequacy
• Housing standards
• Rate of population growth

10. Health Policy Indicators

• Political commitment to Health for All
• Resource allocation for health (% GDP on health)
• Degree of equity in distribution of health services
• Community involvement in health programmes
• Organizational framework and managerial processes

11. Indicators of Quality of Life

(a) Physical Quality of Life Index (PQLI)

• Composite of: Infant Mortality Rate + Life Expectancy at age 1 + Literacy rate
• Scale: 0 to 100

(b) Human Development Index (HDI)

• UNDP composite index of:
  • Life expectancy
  • Adult literacy + mean years of schooling
  • Per capita income (PPP)

(c) QALY (Quality-Adjusted Life Year)

• Combines quantity (years of life) + quality of life
• Used in health economic assessments
• 1 QALY = 1 year of life in perfect health (value = 1.0)
• Death = 0.0

(d) DALY (Disability-Adjusted Life Year)

"DALY is a measure of overall disease burden, expressed as number of years lost due to ill-health, disability, or early death."

• YLL = Years of Life Lost (premature mortality)
• YLD = Years Lived with Disability (morbidity)
• 1 DALY = 1 year of healthy life lost
• Developed by Harvard University for World Bank (1990); adopted by WHO in 2000
• Japanese life expectancy used as standard (longest in world)

(e) Disability-Free Life Expectancy (DFLE)

• Average years expected to live free of disability

WHO "Health for All" Indicators (4 Categories)

WHO Global Reference List of Health Indicators (SDG Era)

1. Health status (mortality, morbidity, fertility)
2. Risk factors (tobacco, obesity, alcohol, unsafe water)
3. Service coverage (immunization, ANC, HIV treatment)
4. Health systems (health workers density, UHC index)