---

DETAILED ANSWERS - K. PARK

---

1. Levels of Prevention & Modes of Intervention (with examples)

A. Primordial Prevention

• Aims to prevent the emergence and establishment of social, economic, and cultural patterns of living that are known to contribute to elevated risk of disease.
• Directed at the whole population.
• Example: Preventing childhood obesity by promoting healthy dietary habits in schools; anti-tobacco policies before smoking habits develop.

B. Primary Prevention

1. Health Promotion - non-specific measures to raise general health:
   • Health education
   • Adequate nutrition
   • Attention to personality development
   • Provision of adequate housing, recreation, pleasant working conditions
   • Marriage counselling
   • Genetic counselling
   • Example: Balanced diet campaigns
2. Specific Protection - measures to protect against a specific disease:
   • Immunization
   • Use of specific nutrients (iodized salt for goitre)
   • Chemoprophylaxis (malaria prophylaxis)
   • Protection against occupational hazards
   • Protection from accidents
   • Example: OPV vaccination against polio

C. Secondary Prevention

• Screening programmes (PAP smear, mammography)
• Case finding and case holding
• Goal: to cure the patient, reduce severity, prevent complications, prevent transmission
• Example: Blood sugar screening for early diabetes detection

D. Tertiary Prevention

• Disability limitation: Prevent further deterioration, limit disease complications
  • Example: Physiotherapy after stroke to prevent contractures
• Rehabilitation: Restore function to maximum possible level
  • Medical rehabilitation, Vocational rehabilitation, Social rehabilitation, Psychological rehabilitation
  • Example: Prosthesis fitting after amputation

K. Park, Preventive & Social Medicine

---

2. Classification of Epidemiological Study Designs

A. Observational Studies

1. Descriptive Studies
   • Case reports
   • Case series
   • Cross-sectional (prevalence) studies
   • Ecological (correlational) studies
2. Analytical Studies
   • Case-Control study (retrospective)
   • Cohort study (prospective or retrospective)

B. Experimental Studies

1. Randomized Controlled Trial (RCT)
2. Field trials
3. Community trials

---

Steps of RCT (Randomized Controlled Trial)

1. Selection of study population - define eligibility criteria (inclusion/exclusion)
2. Baseline assessment - measure outcome variables at start
3. Randomization - random allocation to experimental and control groups
4. Blinding (single/double/triple blind)
5. Intervention - apply treatment to experimental group, placebo to control
6. Follow-up - observe both groups for same duration
7. Assessment of outcome - measure and compare
8. Analysis - statistical comparison (Intention-to-treat analysis)

Types of Blinding

• Single blind: Only patient is unaware of group allocation
• Double blind: Both patient and investigator are unaware
• Triple blind: Patient, investigator, and data analyst are all unaware
• Advantages: Eliminates observer bias, subject bias

Advantages of RCT

• Gold standard for causation
• Controls for confounding (known and unknown)
• Allows direct comparison

Disadvantages of RCT

• Expensive and time-consuming
• Ethical constraints (cannot withhold proven treatment)
• Not suitable for rare diseases
• Hawthorne effect
• Volunteer bias
• Not generalizable (selected population)
• Loss to follow-up is a problem

---

3. Characteristics of Indicators & Health Indicators

Characteristics of a Good Indicator (K. Park)

1. Valid - actually measures what it is supposed to measure
2. Reliable/Reproducible - consistent results under different conditions
3. Sensitive - can detect change
4. Specific - reflects only the situation under consideration
5. Feasible - available from existing data
6. Relevant - relevant to the objective

Indicators of Health

1. Mortality indicators - IMR, MMR, CDR, ASMR, PSMR, Life expectancy
2. Morbidity indicators - Incidence, Prevalence, Notification rates, Hospital admission rates
3. Disability indicators - DALY, QALY, bed disability days
4. Nutritional status indicators - Anthropometric indices, BMI
5. Health care delivery indicators - Bed:population ratio, Doctor:population ratio, IFA tablet coverage
6. Utilization rates - ANC coverage, % institutional deliveries, immunization coverage
7. Social and mental health indicators - crime rates, dependency ratio
8. Environmental indicators - Air/water quality indices
9. Socioeconomic indicators - Per capita income, literacy rate, unemployment

Human Development Index (HDI)

• Introduced by UNDP (1990)
• Composite index combining:
  1. Health: Life expectancy at birth
  2. Education: Mean years of schooling + Expected years of schooling
  3. Standard of living: GNI per capita (PPP)
• HDI = Geometric mean of the three normalized indices

Disability Indicators

• DALY (Disability-Adjusted Life Year): = Years of life lost (YLL) + Years lived with disability (YLD)
• QALY (Quality-Adjusted Life Year): life years x quality-of-life weight (0=death, 1=perfect health)

Morbidity Indicators

• Incidence rate, Prevalence rate, Disease notification rates, Hospital admission rates, Sickness absence rates

Mortality Indicators

• Crude Death Rate, Age-specific mortality rate, Infant Mortality Rate (IMR), Under-5 Mortality Rate, Maternal Mortality Rate (MMR), Perinatal Mortality Rate, Standardized Mortality Ratio (SMR)

---

4. Ergonomics - Definition and Importance

Definition

Importance (K. Park)

1. Increases efficiency and productivity
2. Reduces occupational diseases and injuries
3. Prevents fatigue and accidents
4. Improves worker comfort and morale
5. Reduces absenteeism
6. Helps in designing tools, machines, workplaces for optimal human use
7. Reduces musculoskeletal disorders
8. Improves quality of output

Applications

• Workplace design
• Tool design
• Shift work scheduling
• Human-computer interface
• Industrial safety

---

5. PEM (Protein-Energy Malnutrition)

Common Nutrition Problems in Children

1. PEM (Protein-Energy Malnutrition)
2. Vitamin A deficiency
3. Nutritional anaemia (Iron deficiency)
4. Iodine deficiency disorders
5. Rickets (Vitamin D deficiency)
6. Vitamin C deficiency (Scurvy)

PEM - Definition

Causes of PEM

• Inadequate dietary intake (poverty, ignorance, food taboos)
• Infections (measles, diarrhoea, respiratory infections - increase demand + reduce intake)
• Early weaning from breastfeeding
• Low birth weight
• Large family size
• Poor complementary feeding

Epidemiology

• Most common in children 6 months to 5 years
• Prevalent in developing countries
• India: ~35% children under 5 are stunted
• Marasmus more common under 1 year; Kwashiorkor more 1-3 years

Clinical Forms

Prevention of PEM

• Breastfeeding promotion (exclusive for 6 months)
• Timely, adequate complementary feeding
• ICDS programme
• Nutrition education
• Growth monitoring
• Family planning (spacing births)
• Control of infections
• Fortification of foods
• Nutritional rehabilitation centres

Under-5 Assessment Methods

• Weight for age (Wellcome classification, IAP classification)
• Weight for height (acute malnutrition/wasting)
• Height for age (chronic malnutrition/stunting)
• MUAC (Mid-Upper Arm Circumference) - quick field tool
  • <11.5 cm = SAM; 11.5-12.5 cm = MAM; >12.5 cm = normal
• Gomez classification (based on % of expected weight for age):
  • Grade I: 76-90%; Grade II: 61-75%; Grade III: <60%
• IAP classification: Grade I: 71-80%; Grade II: 61-70%; Grade III: 51-60%; Grade IV: <50%

---

6. Measures of Central Tendency & Limitations

Three main measures:

A. Mean (Arithmetic Mean)

• Sum of all values divided by the number of values
• Advantages: Uses all data, mathematically tractable
• Limitations: Affected by extreme values (outliers); not suitable for skewed distributions

B. Median

• Middle value when data arranged in order
• Not affected by extreme values
• Limitations: Ignores most of the data; cannot be combined mathematically

C. Mode

• Most frequently occurring value
• Limitations: May not exist or may be multiple; crude measure; not unique

General Limitations

• Cannot describe the spread/variability of data
• Central tendency alone is insufficient for comparing distributions
• Need measures of dispersion (range, SD, variance) along with them

---

7. Secondary Attack Rate (SAR)

Key Points (K. Park)

• Excludes the primary case from numerator and denominator
• Excludes those already immune (vaccinated or previously infected)
• Measures transmissibility (infectiousness) of an agent
• Useful in:
  • Measuring household spread
  • Evaluating vaccine efficacy
  • Assessing communicability of disease
  • Comparing strains of pathogens
• Example: In a household of 5 (1 primary case), if 3 of the remaining 4 susceptible contacts develop disease, SAR = 3/4 x 100 = 75%

---

8. Louis Pasteur (1822-1895)

Contributions

1. Germ theory of disease - proved microorganisms cause disease
2. Disproved spontaneous generation theory
3. Developed Pasteurization (heating milk at 63°C/30 min to destroy pathogens)
4. Vaccines:
   • Chicken cholera vaccine
   • Anthrax vaccine (demonstrated publicly at Pouilly-le-Fort, 1881)
   • Rabies vaccine (1885) - first human use on Joseph Meister
5. Developed concept of attenuation of virulence
6. Contributed to understanding of fermentation
7. Work on puerperal fever (sepsis)

Famous Quote from K. Park

---

9. ESI Act (Employees' State Insurance Act, 1948)

Definition of ESI

Scope

• Applies to all factories employing 10 or more persons (using power) or 20 or more (without power)
• Extended to shops, hotels, restaurants, cinemas, road transport
• Employees earning up to Rs. 21,000/month are covered (threshold as per amendments)

Contributions

• Employee: 0.75% of wages
• Employer: 3.25% of wages
• State government contributes 1/8th of total cost of medical benefit

Benefits Under ESI (Social Security Benefits)

1. Sickness benefit - 70% of wages for 91 days/year
2. Extended sickness benefit - for long-term illnesses (34 specified diseases) - up to 2 years
3. Enhanced sickness benefit - 100% wages for sterilization operations
4. Maternity benefit - 100% wages for 26 weeks (plus 6 weeks for miscarriage/MTP)
5. Disablement benefit:
   • Temporary disablement: 90% wages
   • Permanent disablement: pension based on degree of disability
6. Dependants' benefit - pension to dependants in case of death due to employment injury
7. Medical benefit - full medical care to insured person and family
8. Funeral expenses - up to Rs. 10,000
9. Unemployment allowance (Rajiv Gandhi Shramik Kalyan Yojana)
10. Vocational rehabilitation

Social Security Measures

---

10. Epidemiological Triad

Components

• Biological agents: bacteria, viruses, parasites, fungi
• Physical agents: radiation, heat, noise
• Chemical agents: poisons, allergens
• Nutritional agents: deficiencies, excesses
• Social/psychological agents

• Age, sex, race
• Genetic make-up
• Nutritional status
• Immune status
• Occupation, socioeconomic status
• Habits and customs (smoking, diet)
• Pre-existing disease

• Physical: Climate, geography, season, temperature
• Biological: Vectors, reservoirs, food, water
• Socioeconomic: Crowding, sanitation, education, poverty, cultural practices

Disease Causation

• Health = equilibrium between Agent-Host-Environment
• Disease occurs when this equilibrium is disturbed
• The Leavell and Clark model (natural history of disease) is based on this triad
• Web of causation (MacMahon) - multiple interacting factors

---

11. Genetic Counselling

Definition (K. Park)

Objectives

1. Identify individuals and families at risk of hereditary disease
2. Explain the nature, prognosis, and management of the disorder
3. Inform about risk of recurrence
4. Help make informed reproductive decisions
5. Provide psychological support

Indications

1. Couples with a previous child with genetic disorder
2. Advanced maternal age (>35 years) - risk of Down syndrome
3. Consanguineous marriages
4. Family history of genetic disease
5. Previous stillbirth or multiple abortions
6. Known carrier status
7. Abnormal antenatal screening (raised AFP, abnormal USG)
8. Chromosomal abnormality in a parent

Components

1. Diagnosis - clinical, biochemical, chromosomal, molecular
2. Risk assessment - Mendelian risk, empirical risk
3. Communication - non-directive, non-judgmental counselling
4. Decision-making support
5. Follow-up

Methods of Prenatal Diagnosis

• Amniocentesis (15-18 weeks) - chromosomal analysis, biochemical tests
• Chorionic villus sampling (CVS) (9-12 weeks) - earlier than amniocentesis
• Fetal blood sampling (Cordocentesis)
• Ultrasonography - structural abnormalities
• Alpha-fetoprotein (AFP) - neural tube defects
• Triple/Quadruple screening

---

12. Positive Health

Definition (K. Park)

• Physical fitness
• Mental well-being
• Social adaptability
• Capacity to live a full life
• Functioning at optimal capacity

Dimensions of Positive Health

1. Physical dimension - ability to perform daily activities without fatigue
2. Mental dimension - positive self-concept, ability to cope with stress
3. Social dimension - ability to interact satisfactorily
4. Spiritual dimension - sense of purpose and meaning
5. Emotional dimension - ability to express emotions appropriately
6. Vocational dimension - ability to perform productive work

---

13. Acculturation & Culture

Definition of Culture

Definition of Acculturation

Modes of Acculturation (Berry's model)

1. Assimilation - fully adopts new culture, abandons original
2. Integration/Biculturalism - maintains original culture + adopts new culture
3. Separation - maintains original culture, rejects new culture
4. Marginalization - rejects both original and new culture

Public Health Significance (K. Park)

• Affects dietary habits (may improve or worsen nutrition)
• Changes health-seeking behaviour
• Affects reproductive practices
• Changes risk behaviours (smoking, alcohol)
• Migrants undergo acculturation stress ("culture shock")
• Can lead to loss of protective traditional practices

---

14. Case-Control Study

Definition

• Cases = persons with the disease of interest
• Controls = persons without the disease, matched to cases
• Both groups are investigated for past exposure to the suspected risk factor

Steps of Case-Control Study

1. Selection of cases - define disease (diagnostic criteria); source: hospital or population
2. Selection of controls - matched for age, sex, place; free from disease
3. Matching - individual or frequency matching
4. Measurement of exposure - history, records, biological samples
5. Data collection - interview, questionnaire
6. Analysis - Odds Ratio (OR) calculated
7. Interpretation and conclusion

Measure of Risk: Odds Ratio (OR)

• OR >1: exposure associated with increased risk
• OR <1: protective factor
• OR = 1: no association

Advantages

• Suitable for rare diseases
• Quick and relatively inexpensive
• Can study multiple exposures
• No long follow-up needed
• Suitable for diseases with long latency

Disadvantages

• Cannot establish temporality (cause before effect)
• Susceptible to recall bias
• Cannot directly calculate incidence or relative risk
• Selection of appropriate controls is difficult
• Susceptible to selection bias
• Not suitable for rare exposures

---

15. Occupational Diseases

Classification of Occupational Diseases (K. Park)

1. Pneumoconioses - dust diseases of the lung:
   • Silicosis (silica dust)
   • Coal workers' pneumoconiosis (coal dust)
   • Asbestosis (asbestos)
   • Byssinosis (cotton dust)
   • Bagassosis (sugarcane dust)
   • Farmer's lung (mouldy hay)
2. Occupational cancers - lung (asbestos, arsenic), bladder (benzidine), skin (tar/soot)
3. Occupational dermatoses - contact dermatitis, eczema
4. Occupational deafness - noise-induced hearing loss
5. Metal poisoning - lead, mercury, arsenic
6. Heat disorders - heat stroke, heat cramps
7. Radiation sickness
8. Musculoskeletal disorders - repetitive strain injury

Prevention Measures

• Substitution - replace hazardous material with safer one
• Enclosure/isolation of process
• Ventilation - local exhaust, general dilution
• Personal Protective Equipment (PPE) - masks, gloves, goggles
• Pre-employment and periodic medical examination
• Health education
• Rotation of workers

• Pre-placement medical examination
• Periodic/surveillance examinations
• Biological monitoring
• Early detection and treatment

Medical Measures

• Pre-placement examination
• Periodic examination
• Biological monitoring
• Return-to-work examination

Legislations

1. ESI Act 1948 - benefits for employment injuries, sickness, maternity
2. Factories Act 1948 - working conditions, safety provisions
   • Hours of work: max 48 hrs/week, 9 hrs/day
   • Weekly rest day
   • Annual leave with wages
   • Provisions for welfare: canteen, crèche, rest rooms
   • Safety provisions: fencing, safety appliances

---

16. Cohort Study

Definition

Types

1. Prospective cohort - follow forward from present; expensive but less bias
2. Retrospective cohort (historical cohort) - look backward from present using past records; less expensive but depends on record quality
3. Ambidirectional - combination

Elements of Cohort Study

1. Definition of cohort (exposed and unexposed groups)
2. Baseline assessment
3. Follow-up period
4. Identification of new cases
5. Computation of incidence rates

Steps

1. Define study population
2. Select exposed and non-exposed groups
3. Baseline data collection
4. Follow-up (regular intervals)
5. Measure outcome (incidence)
6. Calculate Relative Risk (RR)
7. Calculate Attributable Risk (AR)

Measures of Risk

• Relative Risk (RR) = Incidence in exposed / Incidence in unexposed
  • RR >1: positive association
  • RR = 1: no association
  • RR <1: protective
• Attributable Risk (AR) = Incidence in exposed - Incidence in unexposed
  • Shows excess risk due to exposure
• Population Attributable Risk (PAR)
• Attributable Risk % (AR%) = (RR-1)/RR x 100

Advantages

1. Can directly calculate incidence and RR
2. Can study multiple outcomes
3. Establishes temporal sequence
4. Minimizes recall bias
5. Can measure rare exposures

Disadvantages

1. Expensive and time-consuming
2. Not suitable for rare diseases
3. Loss to follow-up is a problem
4. Changes in exposure or diagnostic criteria over time
5. Not suitable for long latency diseases (unless retrospective)

Cohort vs Case-Control

---

17. Role of Family in Health and Disease

Role of Family (K. Park)

1. Genetic transmission of diseases (consanguinity increases risk)
2. Shared environment - transmission of infections, common exposure to pollutants
3. Dietary habits - family shapes food patterns
4. Psychosocial support - protective against mental illness
5. Health-seeking behaviour - family influences when and where to seek care
6. Compliance with treatment
7. Socialisation - teaching health behaviours
8. Transmission of cultural practices - some protective, some harmful (tobacco, alcohol)

Role of Emotions in Health

• Stress, anxiety, depression can:
  • Suppress immune function (psychoneuroimmunology)
  • Raise blood pressure (hypertension)
  • Worsen diabetes (hyperglycaemia)
  • Precipitate coronary artery disease
  • Contribute to peptic ulcer (Helicobacter pylori + stress)
  • Cause psychosomatic diseases
• Positive emotions (happiness, social support) are protective
• Family dysfunction leads to substance abuse, depression, domestic violence
• Bereavement (loss of spouse) significantly increases mortality
• Social support is a determinant of health

---

18. Integrated Vector Control

Definition

Methods of Vector Control (K. Park)

• Eliminating breeding sites
• Drainage of stagnant water
• Filling ditches and pits
• Intermittent irrigation
• House screening
• Example: Removing stagnant water to prevent Aedes breeding

• Larvivorous fish (Gambusia, Lebistes) in ponds/water bodies
• Bacillus thuringiensis israelensis (Bti) - bacterial larvicide
• Predators and parasites

• Larvicides: Temephos, Malathion
• Adulticides: DDT (indoor residual spraying), pyrethroid sprays
• Space spraying (fogging)
• Ultra-low volume (ULV) spraying

• Repellents (DEET)
• Insecticide-treated bed nets (ITNs)
• Protective clothing

• Sterile insect technique
• Genetically modified mosquitoes (Wolbachia)

Principles of Integrated Vector Management

• Combining methods increases effectiveness
• Reduces development of resistance
• More cost-effective
• Environmentally friendly
• Requires community participation

---

19. Definition of Health, Spectrum of Health, Dimensions

Definition of Health (WHO, 1948)

Spectrum of Health (K. Park)

• No sharp distinction between health and disease
• Disease is an adjustment or reaction of host to the environment
• The "iceberg phenomenon" - only the tip of disease is visible clinically; subclinical disease is hidden below the surface

Determinants of Health (K. Park)

1. Biological/Constitutional factors - age, sex, genetic makeup
2. Behavioural and social factors - smoking, diet, exercise, education
3. Environment - physical, biological, socioeconomic
4. Standard of living - income, poverty
5. Health services - access, quality, utilization
6. Nutrition
7. Political/Economic factors - governance, policies

Dimensions of Health

1. Physical
2. Mental
3. Social
4. Spiritual
5. Emotional
6. Vocational (functional)
7. Cultural
8. Political

---

20. Indian Reference Man

Definition (ICMR/K. Park)

Characteristics (ICMR):

• Age: 20-39 years
• Weight: 60 kg (originally 55 kg, now revised to 60 kg)
• Height: 163 cm (approx)
• Healthy, free from disease
• Moderately active occupation
• Lives in a temperate climate (mean external temperature 10-25°C)

Indian Reference Woman:

• Age: 20-39 years
• Weight: 55 kg (originally 45 kg)
• Healthy, not pregnant or lactating
• Moderately active

Uses

• Basis for calculating Recommended Dietary Allowances (RDA)
• Comparing dietary requirements across populations
• Nutritional planning at national level

---

21. Superchlorination

Definition

Classification of Water Treatment Methods (K. Park)

1. Boiling
2. Storage and sedimentation
3. Filtration (slow sand, rapid sand)
4. Exposure to sunlight (UV radiation)
5. Screening/straining

1. Chlorination - most common, cheapest, effective
2. Coagulation - alum (aluminum sulphate), ferric sulphate
3. Iodination (field/emergency)
4. Potassium permanganate

Types of Chlorination

1. Plain chlorination - add small amount of chlorine
2. Pre-chlorination - before filtration
3. Post-chlorination - after filtration
4. Super-chlorination - add 1-15 mg/L chlorine; follow with dechlorination
5. Breakpoint chlorination - add chlorine till "breakpoint" (all impurities oxidized) then free residual chlorine remains

Process of Superchlorination

1. Add excess chlorine (5-15 mg/L)
2. Destroys all pathogens, removes taste/odour-causing compounds
3. Dechlorinate with sodium thiosulphate or activated carbon to make palatable
4. Used in emergencies, swimming pools, heavily contaminated water

---

22. Vitamin A Deficiency

Definition

Ocular Manifestations (Xerophthalmia - WHO Classification)

Other Manifestations

• Growth retardation
• Increased susceptibility to infections (measles becomes fatal)
• Follicular hyperkeratosis (toad skin)
• Anaemia
• Reproductive failure

Prevention

1. Dietary approach: Green leafy vegetables, yellow-orange fruits, animal foods
2. Supplementation (NPCB/GoI schedule):
   • 6-11 months: 1 lakh IU (one dose)
   • 12-23 months: 2 lakh IU (every 6 months)
   • 24-59 months: 2 lakh IU (every 6 months)
3. Food fortification (vitamin A fortified edible oil, vanaspati)
4. Nutrition education

---

23. Pre-Placement and Periodic Medical Examinations

Pre-Placement (Pre-Employment) Examination

1. Assess baseline health status
2. Identify pre-existing conditions that may be worsened by the job
3. Match the worker to the job (job fitness)
4. Serve as baseline for future comparison
5. Legal protection for employer
6. Detect contraindications to particular work

• Medical history
• Physical examination (vision, hearing, musculoskeletal)
• Investigations (CBC, LFT, RFT, chest X-ray, audiometry, spirometry)
• Specific tests based on job (e.g., lead levels for battery workers)

Periodic (Surveillance) Examination

1. Detect early signs of occupational disease
2. Monitor progression of known disease
3. Assess effectiveness of preventive measures
4. Update baseline records
5. Provide individual health counselling
6. Early detection allows early intervention

Importance

• Legally required under Factories Act for certain hazardous occupations
• Primary tool of occupational health surveillance
• Protects both workers and employers
• Forms basis of biological monitoring

---

24. Incidence vs Prevalence

Relationship

• Long-duration diseases (chronic diseases) have higher prevalence
• Short-duration diseases (acute) have lower prevalence relative to incidence

Types of Incidence

• Cumulative incidence (Incidence proportion) - proportion developing disease over a period
• Incidence density/rate - accounts for person-time at risk

Types of Prevalence

• Point prevalence - at a specific moment
• Period prevalence - during a defined period

---

25. Lead Time

Definition

Significance (K. Park)

• Lead time bias is a major bias in evaluating screening programmes
• If lead time is not accounted for, a screening programme may appear to improve survival (in years from diagnosis to death) even if it does not actually alter the natural course of the disease
• Example: Disease detected at screening at age 40, would have been detected symptomatically at age 43. Lead time = 3 years. If patient dies at age 45, survival appears 5 years (from screening) vs 2 years (without screening) - but the patient lived the same amount of time.
• Lead time bias makes screening programmes look better than they are unless properly adjusted.

---

26. Investigation of an Epidemic

Definition of Epidemic

Definition of Epidemiology (K. Park)

Aims/Uses of Epidemiology

1. Describe the distribution and determinants of disease
2. Identify risk factors
3. Plan and evaluate health services
4. Control and prevent disease
5. Test preventive measures
6. Study natural history of disease

Steps in Investigation of an Epidemic

1. Verify the diagnosis - confirm cases are real (lab tests)
2. Confirm the existence of an epidemic - compare with expected rates (baseline data)
3. Define a case - establish case definition (clinical/lab criteria)
4. Count cases and describe in terms of Person, Place, Time (Epidemiological Triad)
5. Draw an epidemic curve (histogram of cases by time of onset)
6. Identify source and mode of transmission - food, water, person-to-person
7. Formulate a hypothesis - what is the source and cause?
8. Test the hypothesis - analytical study (case-control or cohort in outbreak)
9. Institute control measures - immediate (remove source) and long-term
10. Evaluate control measures
11. Prepare a report

Epidemic Curve Types

• Point source epidemic: sharp rise and rapid fall (common vehicle)
• Propagated epidemic: slow rise, multiple peaks (person-to-person spread)
• Combined pattern: starts point source, then propagates

---

27. Disinfection

Definition

Types of Disinfection

• Immediate disinfection of infectious material (discharges, excretions) as it leaves the patient's body
• Done while the patient is still ill
• Example: Disinfecting stools of cholera patient in bedpan

• Thorough disinfection of room and all articles after patient has been removed (cured, transferred, or died)
• Example: Fumigation of room after infectious patient is discharged

• Use of gaseous disinfectants (formaldehyde, chlorine) to fill a room
• Now less commonly used; has been replaced by surface disinfection

Methods of Disinfection

• Heat (boiling, autoclave, dry heat)
• UV radiation
• Pasteurization

• Phenol and cresols - Lysol (black fluid); standard phenol coefficient test
• Halogens: Chlorine, iodine, iodophors
• Aldehydes: Formaldehyde, glutaraldehyde
• Alcohols: Ethyl alcohol (70%), isopropyl alcohol
• Quaternary ammonium compounds (QAC): Cetrimide
• Heavy metals: Mercury (Mercurochrome), silver nitrate
• Oxidizing agents: Potassium permanganate, hydrogen peroxide

Disinfectant Efficiency

---

28. Nutritional Surveillance & Anthropometric Indices

Nutritional Surveillance (K. Park)

Methods of Nutritional Surveillance

1. Anthropometric assessment (most common)
2. Dietary surveys
3. Biochemical/laboratory tests
4. Clinical examination
5. Vital statistics / indirect indicators (IMR, growth data)

Anthropometric Indices for Nutritional Status in Children

Cut-offs (WHO 2006 Growth Standards)

• Underweight: W/A < -2 SD (moderate) / < -3 SD (severe)
• Stunting: H/A < -2 SD (moderate) / < -3 SD (severe)
• Wasting: W/H < -2 SD (moderate) / < -3 SD (severe)

MUAC Cut-offs (6-59 months)

• <11.5 cm = Severe Acute Malnutrition (SAM)
• 11.5-12.5 cm = Moderate Acute Malnutrition (MAM)

• 12.5 cm = Normal

Nutrition Problems List (India, K. Park)

1. Protein-Energy Malnutrition (PEM) / Undernutrition
2. Vitamin A deficiency (Xerophthalmia)
3. Iron deficiency anaemia
4. Iodine deficiency disorders (goitre, cretinism)
5. Vitamin D deficiency (Rickets in children)
6. Vitamin B complex deficiencies (Beriberi, Pellagra)
7. Vitamin C deficiency (Scurvy)
8. Obesity / Overnutrition (emerging epidemic)
9. Fluorosis (endemic - excess fluoride)

---