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🩺 PSM - Communicable Diseases: Exam Summary

(Source: Park's Textbook of Preventive & Social Medicine)

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1. KEY DEFINITIONS (High-Yield for MCQs)

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2. CHAIN OF INFECTION (Must Know!)

Infectious Agent → Reservoir → Portal of Exit → Mode of Transmission
        → Portal of Entry → Susceptible Host

Modes of Transmission:

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3. TUBERCULOSIS (TB) - Top Priority

Epidemiology (Key Numbers):

• ~1/3 of global population is asymptomatically infected
• 5-10% of infected will develop clinical disease in lifetime
• One infectious case can infect 10-15 persons/year
• India has 26% of global TB burden (highest)
• MDR-TB: 3.3% of new cases; 18% of previously treated cases

Risk Factors:

Control Strategies:

• 90% reduction in TB deaths
• 80% reduction in new cases
• Zero catastrophic costs for families

• 40 million people treated for TB
• 30 million people given TB preventive treatment
• USD 13 billion/year funding

Anti-TB Drugs - First Line (Mnemonic: RIPE or SHREP):

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4. IMPORTANT DISEASES AT A GLANCE

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5. LEVELS OF PREVENTION (Must Know!)

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6. VACCINES - HIGH YIELD

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7. EPIDEMIOLOGICAL TRIAD

         Agent
           |
    Host - - - Environment

• Agent factors: Infectivity, pathogenicity, virulence, toxigenicity, antigenicity
• Host factors: Age, sex, immunity, nutritional status, genetics
• Environmental factors: Physical, biological, social environment

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8. DISEASE CONTROL MEASURES

1. Control at source (reservoir): Treatment of cases, isolation, quarantine, animal control
2. Breaking transmission: Safe water, food hygiene, vector control, condom use
3. Protection of susceptible host: Vaccination, chemoprophylaxis, health education

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9. QUICK MCQ FACTS

• Smallpox = only disease eradicated globally
• Diseases amenable to eradication: Measles, Diphtheria, Polio, Guinea worm
• Herd immunity = when enough of a population is immune, protecting even non-immune individuals
• Incubation period = time between infection and first symptom
• Generation time = time between infection and peak infectivity
• R0 (Basic Reproduction Number): Measles ~12-18 (highest), COVID-19 ~2-3
• RNTCP (now Ni-kshay/National TB Elimination Programme) - India's TB program

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10. IMPORTANT MNEMONICS

Political commitment, Case detection by sputum smear microscopy, Standardized short-course chemotherapy, Uninterrupted drug supply, Recording and reporting system

Chickenpox, Aspergillosis, Varicella, Tuberculosis, Measles

Typhoid, Cholera, Hepatitis A & E, Polio, Amoebiasis

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📚 PSM COMPLETE EXAM SUMMARY

(Park's Textbook of Preventive & Social Medicine)

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SECTION 1: EPIDEMIOLOGY & BIOSTATISTICS

1.1 What is Epidemiology?

"The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to control of health problems."

1. Describe distribution & magnitude of health/disease in populations
2. Identify aetiological factors (risk factors) in pathogenesis
3. Provide data for planning, implementation & evaluation of health services

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1.2 Types of Epidemiological Studies

Epidemiological Studies
├── Observational
│   ├── Descriptive (Who? When? Where?)
│   └── Analytical
│       ├── Case-Control (Odds Ratio)
│       └── Cohort (Relative Risk)
└── Experimental / Interventional
    ├── RCT
    └── Field / Community trials

Descriptive Epidemiology - asks 3 questions:

• When - time distribution (secular trends, seasonal variation)
• Where - place distribution (endemic zones, spot maps)
• Who - person distribution (age, sex, occupation, race)

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1.3 Key Epidemiological Measures (HIGH YIELD MCQs!)

Rates:

Incidence vs Prevalence:

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1.4 Screening

1. Important health problem
2. Acceptable treatment available
3. Facilities for diagnosis & treatment available
4. Recognizable latent/early symptomatic stage
5. Suitable test/examination available
6. Test acceptable to population
7. Natural history of disease understood
8. Agreed policy on whom to treat
9. Cost economically balanced
10. Case-finding is a continuing process

• Sensitivity = TP / (TP+FN) - ability to detect true cases ("no miss") → used for serious diseases
• Specificity = TN / (TN+FP) - ability to correctly exclude non-cases → used to confirm diagnosis
• PPV = TP / (TP+FP) - depends on prevalence
• NPV = TN / (TN+FN) - depends on prevalence

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1.5 Biostatistics Basics

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SECTION 2: COMMUNICABLE DISEASES

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SECTION 3: NUTRITION & DISEASE PREVENTION

3.1 Protein-Energy Malnutrition (PEM)

Grading Malnutrition (IAP Classification - Weight for Age):

NFHS-4 Key Statistics (India):

• 18.5% children born with low birth weight
• 35.7% underweight
• 38.4% stunted (chronic malnutrition - height for age)
• 21% wasted (acute malnutrition - weight for height)
• 33% adult men and 36% adult women have BMI <18.5

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3.2 Micronutrient Deficiency Diseases

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3.3 National Nutrition Programmes (India)

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3.4 Balanced Diet

• Sedentary adult man: ~2320 kcal/day
• Sedentary adult woman: ~1900 kcal/day
• Pregnant woman: additional 350 kcal/day
• Lactating woman: additional 600 kcal/day

• Carbohydrates: 60-70% of total calories (main energy source)
• Proteins: 10-15% of total calories (1g/kg/day for adults)
• Fats: 20-30% of total calories

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SECTION 4: HEALTH PROGRAMS & NATIONAL POLICIES

4.1 Health System Structure (India)

Sub-centre (5000 pop plains / 3000 hilly)
     ↓
Primary Health Centre - PHC (30,000 plains / 20,000 hilly) - 6 beds
     ↓
Community Health Centre - CHC (80,000-1,20,000) - 30 beds
     ↓
District Hospital
     ↓
Medical College Hospital

PHC - Key Facts:

• Bhore Committee (1946) first gave the concept
• Functions cover all 8 essential elements of Alma-Ata (1978)
• As of 2017: 25,650 PHCs in India
• Staffed by: Medical Officer, ANM, MPW, Health Inspector, Lab technician

Sub-Centre Staff:

• 1 ANM (Auxiliary Nurse Midwife) + 1 MPW (Male)

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4.2 National Health Mission (NHM)

• NRHM - National Rural Health Mission
• NUHM - National Urban Health Mission

• 1 per 1000 rural population
• Bridge between community and health system
• Key roles: immunization, ANC registration, institutional delivery, ORS distribution

• Antenatal care (minimum 4 ANC visits, now ANC1 in first trimester)
• Institutional delivery promotion
• JSSK (Janani Shishu Suraksha Karyakram) - free services

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4.3 Key National Health Programmes

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4.4 Universal Immunization Programme (UIP) - Vaccine Schedule

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4.5 Important Committees & Their Recommendations

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SECTION 5: ENVIRONMENT & OCCUPATIONAL HEALTH

5.1 Water Supply & Purification

Standards:

• Per capita water requirement: 135 litres/day (urban), 40 litres/day (rural minimum)
• WHO permissible coliform count: 0 per 100 mL (drinking water)
• Residual chlorine: 0.2-0.5 mg/litre at consumer end

Water Purification Steps:

1. Storage & Sedimentation (removes large particles, allows sunlight)
2. Coagulation & Flocculation (alum/lime - removes suspended particles)
3. Filtration (Slow Sand Filter OR Rapid Sand Filter)
4. Disinfection (Chlorination - most common)

Slow vs Rapid Sand Filter:

Chlorination:

• Bleaching powder: Ca(OCl)Cl - most widely used
• Super-chlorination: using excess chlorine then removing with Na-thiosulphate
• Break-point chlorination: adding chlorine until all demand is satisfied, residual chlorine appears

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5.2 Air Pollution

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5.3 Occupational Health & Diseases

Occupational Lung Diseases (Pneumoconioses):

Other Occupational Diseases:

ILO/Occupational Health Key Points:

• Occupational health = promotion and maintenance of highest degree of physical, mental, social well-being of workers
• Ergonomics = fitting the job to the worker (not worker to job)
• 3 E's of accident prevention: Engineering, Education, Enforcement

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5.4 Environmental Sanitation

Excreta Disposal Methods:

Solid Waste Disposal:

• Sanitary landfill - most hygienic
• Incineration - for hospital/biomedical waste (most effective for destruction)
• Composting - organic waste → manure
• Biomedical waste classified into 4 categories (Yellow, Red, White/Translucent, Blue bags)

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SECTION 6: LEVELS OF PREVENTION (MEGA HIGH-YIELD)

1. Health promotion
2. Specific protection
3. Early diagnosis & treatment
4. Disability limitation
5. Rehabilitation

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SECTION 7: FAMILY HEALTH & DEMOGRAPHY

7.1 Demographic Indices

7.2 Family Planning

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QUICK REVISION: TOP MCQ FACTS 🎯

1. Alma-Ata (1978) = "Health for All by 2000 AD" via Primary Health Care
2. Ottawa Charter (1986) = Health Promotion (5 action areas: build healthy public policy, create supportive environments, strengthen community action, develop personal skills, reorient health services)
3. Only eradicated disease = Smallpox (1980)
4. India polio-free since March 2014
5. Bhore Committee = father of PHC concept
6. ASHA = 1 per 1000 rural population
7. Herd immunity threshold for measles = 92-95%
8. India's IMR target (NHP 2017) = 28/1000 by 2019 (achieved ~28 in 2020)
9. Most heat-sensitive vaccine = OPV (also Measles)
10. Most common occupational lung disease = Silicosis
11. Schmutzdecke = biological layer in slow sand filter responsible for bacterial removal
12. Bleaching powder = most widely used disinfectant for water
13. DOTS = backbone of TB control (Directly Observed Treatment, Short-course)
14. NMR = best indicator of health services quality
15. IMR = best single indicator of socioeconomic development
16. Incidence used for acute diseases; Prevalence used for chronic diseases
17. Kwashiorkor = protein deficiency + edema; Marasmus = total calorie deficiency + wasting
18. IFA supplementation in pregnancy = 100 mg iron + 500 mcg folic acid daily
19. ANC minimum visits = 4 (WHO recommends 8)
20. ICDS = largest integrated child development programme in the world

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• Complete answer with key facts, numbers and mnemonics below

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• 📖 Key Definitions (13 cards)
• 📊 Epidemiology Measures (6 cards)
• 🔢 Key Numbers (8 cards)
• 🏥 National Programmes (6 cards)
• 🛡️ Disease Prevention (6 cards)
• 🥗 Nutrition (4 cards)
• 🌿 Environment & Occ. Health (4 cards)
• 💡 Mnemonics & Top 15 MCQ facts (4 cards)

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