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Q1. Infectious Disease and Communicable Disease (10 Marks)

Introduction

Definitions

Related Definitions

Chain of Transmission

• Human reservoir - the most important source. Man may be a case or a carrier.
• Animal reservoir - diseases transmitted from animals are called zoonoses (e.g., rabies, plague, anthrax). Subdivided into: anthropozoonoses (animal to man), zooanthroponoses (man to animal), amphixenoses (bidirectional).
• Reservoir in non-living things - soil (tetanus), water (cholera), food.

• By type: Incubatory, Convalescent, Healthy carriers
• By duration: Temporary, Chronic carriers (e.g., typhoid fever, hepatitis B)
• By portal of exit: Urinary, Intestinal, Respiratory, Nasal carriers

• Direct transmission - direct contact, droplet spread (within 1 metre), transplacental
• Indirect transmission - vehicle-borne (food, water, fomites), vector-borne (mechanical or biological), airborne (droplet nuclei, dust)

Other Important Definitions

• Contamination: Presence of an infectious agent on a body surface or inanimate article (does NOT imply carrier state)
• Infestation: Lodgement of arthropods on body surface (e.g., lice, itch mite)
• Nosocomial infection: Infection originating in a patient while in hospital - not present at time of admission (e.g., surgical wound infection, hepatitis B, UTI)
• Opportunistic infection: Infection by normally innocuous organisms when immunological defences are compromised (as in AIDS)
• Iatrogenic disease: Adverse health effects caused by a professional act (e.g., aplastic anaemia following chloramphenicol, hepatitis B after blood transfusion)
• Surveillance: Continuous analysis, interpretation and feedback of systematically collected data to detect trends and initiate control measures
• Eradication: Termination of all transmission globally - to date, only smallpox has been eradicated

Prevention and Control

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Q2. Demographic Cycle and Family Planning, Hormonal Pills (10 Marks)

A. Demographic Cycle

B. Family Planning

1. Proper spacing and limitation of births
2. Advice on sterility
3. Education for parenthood and sex education
4. Screening for reproductive cancers (e.g., cervical cancer)
5. Genetic counselling
6. Premarital consultation and examination
7. Marriage counselling
8. Preparation for first child
9. Adoption services

National Population Policy (NPP) 2000

C. Contraceptive Methods - Hormonal Pills (Oral Contraceptives)

Types

• Contain both estrogen (ethinyl estradiol) and progestogen
• Mechanism of Action: (a) Inhibit ovulation by suppressing FSH and LH via pituitary feedback, (b) Alter cervical mucus making it hostile to sperm, (c) Change endometrial lining preventing implantation, (d) Affect tubal motility

• Contain only progestogen (e.g., norethindrone)
• Do NOT reliably inhibit ovulation
• Act mainly on cervical mucus and endometrium
• Suitable for lactating mothers (unlike combined pills which can suppress lactation)

Efficacy

• Perfect use: failure rate < 1 per 100 woman-years (Pearl Index)
• Typical use: failure rate 3-8 per 100 woman-years

Non-Contraceptive Benefits

• Reduced menstrual blood loss and dysmenorrhoea
• Reduced risk of ovarian and endometrial cancer
• Reduced risk of benign breast disease and ovarian cysts
• Improved acne

Side Effects and Risks

• Nausea, vomiting, headache, breakthrough bleeding (minor)
• Weight gain, mood changes
• Serious: Increased risk of venous thromboembolism (VTE), hypertension, stroke in high-risk women
• Slight increased risk of breast and cervical cancer with long-term use

Contraindications

Pearl Index

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Q3. Define Epidemiology (10 Marks)

Introduction

Definitions of Epidemiology

1. Parkin (1873): "That branch of medical science which treats epidemics."
2. Lilienfeld (1978): "The study of the distribution of a disease or a physiological condition in human populations and of the factors that influence this distribution."
3. John Last (1988): "The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems."
4. International Epidemiological Association (IEA): Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the prevention and control of health problems.

Three Core Components

• Measurement of frequency of disease, disability, or death
• Summarized as rates and ratios (prevalence rate, incidence rate, death rate)
• Rates are essential for comparing disease frequency in different populations
• Comparisons yield clues to disease aetiology

• Disease is NOT uniformly distributed in human populations
• Epidemiology studies distribution patterns by time, place, and person
• Time: Has disease increased or decreased over time?
• Place: Is disease more concentrated in one geographic area?
• Person: Is disease more common in men, a specific age group, or specific behaviour groups?
• This aspect is known as "Descriptive Epidemiology"

• Testing aetiological hypotheses and identifying underlying causes (risk factors)
• Uses epidemiological principles and methods
• Contributes to understanding of chronic diseases (e.g., lung cancer and cardiovascular disease)
• This aspect is known as "Analytical Epidemiology"

Aims of Epidemiology (IEA)

1. To describe the distribution and magnitude of health and disease problems in human populations
2. To identify aetiological factors (risk factors) in the pathogenesis of disease
3. To provide data essential for planning, implementation, and evaluation of preventive and curative health services

Epidemiology vs. Clinical Medicine

Scope and Sub-disciplines

• Infectious disease epidemiology
• Chronic disease epidemiology
• Clinical epidemiology
• Genetic epidemiology
• Occupational epidemiology
• Cancer epidemiology
• Psychosocial epidemiology

Types of Epidemiological Studies

1. Descriptive studies - Describe distribution by time, place, person; generate hypotheses
2. Analytical studies - Test hypotheses; include case-control and cohort studies
3. Experimental/Intervention studies - Evaluate interventions; include RCTs and field trials

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UNIT 2: COMMUNICABLE DISEASES

Complete Exam Answers

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Q1. Infectious Disease and Communicable Disease (10M)

• Communicable disease = illness due to specific infectious agent transmitted from reservoir to susceptible host
• Chain of infection = Reservoir → Modes of Transmission → Susceptible Host
• Key definitions: Epidemic, Endemic, Pandemic, Sporadic, Carrier types, Surveillance, Eradication
• Control: immunization, sanitation, water treatment, infection control practices

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Q2. Dengue (10M)

Introduction

Etiology

• Caused by dengue virus - an RNA flavivirus
• 4 serotypes: DEN-1, DEN-2, DEN-3, DEN-4
• Immunity to one serotype does NOT confer immunity to others; prior immunity to a different serotype increases DHF risk (antibody-dependent enhancement)

Epidemiology

• Vector: Aedes aegypti (primary) and Aedes albopictus (secondary)
• Transmitted by bite of infected female Aedes mosquito
• Endemic in >100 countries; South-East Asia and Western Pacific most affected
• India is in Category A - major public health problem; all 4 serotypes circulating

Clinical Features

1. Classical Dengue Fever (DF)

• Incubation period: 3-14 days (commonly 5-7 days)
• Sudden onset high fever (39°C-40°C), severe headache, retro-orbital pain, myalgia, arthralgia ("breakbone fever")
• Biphasic fever - fever with remission of a few hours to 2 days
• Maculopapular/scarlatiniform rash on 3rd-4th day (appears on chest/trunk, spreads to extremities)
• Leucopenia, thrombocytopenia
• Self-limiting; case fatality extremely low

2. Dengue Haemorrhagic Fever (DHF)

• Febrile phase: High fever, facial flushing, headache, abdominal pain, positive tourniquet test, minor haemorrhages (petechiae, purpura)
• Critical phase (day 3-7): Plasma leakage causing pleural effusion/ascites; if plasma leakage severe → dengue shock syndrome (DSS). Thrombocytopenia <100,000/mm³; haematocrit rises ≥20%
• Recovery phase: Fluid reabsorption, bradycardia, rash with "white islands in sea of red"

3. Severe Dengue (DSS)

• Hypotensive shock with narrow pulse pressure (<20 mmHg) or undetectable BP
• Can lead to multi-organ failure and death if untreated

WHO Grade Classification of DHF

Diagnosis

• NS1 antigen - detectable from day 1-5 (early)
• IgM/IgG ELISA - IgM from day 5 onwards
• CBC - thrombocytopenia, rising haematocrit
• Isolation of virus by cell culture

Treatment

• No specific antiviral; supportive management
• Paracetamol for fever (avoid NSAIDs/aspirin)
• Oral rehydration for DF; IV fluids for DHF
• Blood/platelet transfusion only if severe bleeding
• Close monitoring of haematocrit and platelet count

Prevention and Control

1. Vector control - source reduction (eliminate mosquito breeding sites - stagnant water in containers, tyres, flower pots)
2. Anti-larval measures (Temephos/Abate in water containers)
3. Personal protection (repellents, nets, full-sleeve clothing)
4. Fogging/space spraying during outbreaks (adulticiding with malathion/cypermethrin)
5. Dengue vaccine (Dengvaxia): Live attenuated tetravalent; approved for ages 9-45 in endemic areas; only for seropositive individuals
6. Community awareness and surveillance

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Q3. Mosquito-Borne Diseases (10M)

Introduction

Classification of Mosquito-Borne Diseases

A. Diseases Transmitted by Anopheles Mosquitoes

B. Diseases Transmitted by Culex Mosquitoes

C. Diseases Transmitted by Aedes Mosquitoes

Key Details of Major Mosquito-Borne Diseases

1. Malaria

• Caused by Plasmodium falciparum, P. vivax, P. malariae, P. ovale
• P. falciparum causes malignant tertian malaria - most severe, can cause cerebral malaria
• Typical attack: Cold stage → Hot stage → Sweating stage
• P. vivax: benign tertian (48 hrs); P. malariae: quartan (72 hrs)
• Diagnosis: Peripheral blood smear (gold standard), RDT (HRP-2), PCR
• Treatment: Chloroquine for P. vivax; Artemisinin-based Combination Therapy (ACT) for P. falciparum

2. Japanese Encephalitis (JE)

• Caused by JE virus; vector: Culex tritaeniorhynchus (breeds in paddy fields)
• Reservoir: pigs and wading birds
• Clinical: high fever, neck rigidity, altered consciousness, convulsions
• Case fatality: 25-30%; neurological sequelae in survivors
• Prevention: JE vaccine (SA 14-14-2 live attenuated vaccine used in India)
• Homoeopathic prophylaxis: Belladonna 200 C used under AYUSH in India

3. Filariasis

• Caused by W. bancrofti (90%), Brugia malayi (10%)
• Transmitted by Culex quinquefasciatus in urban settings
• Clinical: lymphadenitis, lymphangitis, elephantiasis, hydrocoele
• Mass Drug Administration (MDA): DEC + Albendazole annually

4. Chikungunya

• Alphavirus; vector: Aedes aegypti
• Clinical: sudden high fever, severe joint pain (can persist months-years), rash
• No specific treatment; supportive care

5. Yellow Fever

• Jungle cycle (monkeys → Aedes) and urban cycle (man → Aedes → man)
• Live attenuated 17D vaccine - single dose, lifelong protection
• International certificate of vaccination required for travel to endemic areas

Control of Mosquito-Borne Diseases - General Principles

1. Source reduction - eliminating breeding sites (most important)
2. Anti-larval measures - Larvicides (Temephos/Abate), Biological control (Gambusia fish), Bacillus thuringiensis israelensis (Bti)
3. Chemical control - Indoor residual spraying (IRS), space spraying/fogging
4. Personal protection - Insecticide-treated nets (ITNs/LLINs), repellents (DEET), protective clothing
5. Biological control - Gambusia fish, Bacillus sphaericus
6. Vaccines where available

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Q4. Disease Transmission and Modes of Transmission (10M)

Introduction

Classification of Modes of Transmission

A. DIRECT TRANSMISSION

• Skin-to-skin, mucosa-to-mucosa transfer
• Examples: STDs, AIDS, leprosy, leptospirosis, skin and eye infections, ringworm

• Direct projection of droplets (>5 µm) during coughing, sneezing, speaking, spitting
• Limited to a distance of 30-60 cm between source and host
• Particles 5 µm or less can reach alveoli
• Examples: respiratory infections, common cold, diphtheria, whooping cough, tuberculosis, COVID-19, meningococcal meningitis

• Direct exposure of susceptible tissue to disease agent in soil
• Examples: hookworm, tetanus, melioidosis, systemic mycoses

• Animal bites (rabies), insect bites (malaria), needlestick injuries (HIV, hepatitis B)

• Congenital infections: rubella, syphilis, HIV, toxoplasmosis, CMV, hepatitis B

B. INDIRECT TRANSMISSION

• Water-borne: Cholera, typhoid, hepatitis A/E, poliomyelitis, dysentery
• Food-borne: Salmonellosis, staphylococcal food poisoning, botulism
• Milk-borne: Typhoid, brucellosis, streptococcal infections, campylobacter
• Fomite-borne: Objects like bedding, clothing, toys, instruments (anthrax spores)

• (a) Mechanical: Pathogen carried externally on vector's body/legs; no multiplication. Example: housefly carries typhoid, dysentery, cholera
• (b) Biological: Pathogen undergoes multiplication or development in vector.
  • Propagative: Pathogen multiplies in vector but no cyclical change (plague bacillus in rat flea)
  • Cyclo-propagative: Undergoes both cyclical change and multiplication (malaria in Anopheles)
  • Cyclo-developmental: Undergoes cyclical change but no multiplication (filariasis in Culex)
  • Transovarian: Pathogen transmitted to offspring of vector (scrub typhus in mites)

• (a) Droplet nuclei: Dried residue of expelled droplets (<5 µm); remain suspended in air for long periods; can travel considerable distances. Examples: tuberculosis, COVID-19, measles, varicella, SARS
• (b) Dust: Dried organisms on floor/surfaces resuspended as dust. Examples: Q fever, psittacosis, coccidioidomycosis

• "Finger-to-mouth" transmission of intestinal pathogens
• Faecal → Finger → Food/water → Host
• Examples: hepatitis A, polio, typhoid, cholera, dysentery

The Epidemiological Triad

• Agent (must be present in sufficient dose)
• Host (must be susceptible)
• Environment (must favour transmission)

Incubation Period and its Importance

• The period between entry of infectious agent and appearance of first symptoms
• Useful for: identifying exposure period, applying quarantine, tracing source of infection

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Q5. COVID-19 Outbreak Steps (10M)

Introduction

Etiology

• SARS-CoV-2: single-stranded RNA virus (betacoronavirus family)
• Named for its spike protein (S protein) that binds to ACE2 receptor on human cells
• Variants of concern (VOC): Alpha, Beta, Delta, Omicron - with varying transmissibility and immune evasion

Epidemiology

• Transmission: primarily respiratory droplets and aerosols (airborne); contact transmission; fomite transmission
• R0 (Basic Reproduction Number): Original strain ~2-3; Delta ~5-7; Omicron ~10-18
• Incubation period: 2-14 days (median 5-6 days)
• Pre-symptomatic and asymptomatic transmission is a key feature
• Higher risk: elderly, immunocompromised, diabetes, hypertension, obesity

Clinical Features

• Asymptomatic (majority)
• Mild to moderate: Fever, dry cough, fatigue, loss of taste/smell (anosmia/ageusia), sore throat, myalgia
• Severe: Pneumonia, hypoxia (SpO2 < 94%)
• Critical: ARDS, septic shock, multi-organ failure
• Post-COVID syndrome: Persistent symptoms >4 weeks (fatigue, brain fog, dyspnoea)

Steps in Outbreak Management (Key 10-mark focus)

Step 1: Detection and Verification

• Passive surveillance (notification from hospitals/labs)
• Active case finding
• Define a case definition (clinical + lab criteria)

Step 2: Confirm the Outbreak

• Confirm diagnosis by laboratory testing (RT-PCR, Rapid Antigen Test)
• Compare current case count with baseline/expected numbers
• Establish that cases exceed normal expectancy

Step 3: Case Finding and Line Listing

• Active case finding in community
• Line list: Record each case's name, age, sex, date of onset, contacts, travel history
• Case classification: Suspect, Probable, Confirmed

Step 4: Contact Tracing and Quarantine

• Identify all close contacts (within 1 metre for >15 minutes)
• Quarantine all contacts for 14 days (incubation period)
• Isolation of confirmed cases (separate from family, ideally in COVID care centres)

Step 5: Epidemiological Investigation

• Construct an epidemic curve (epi curve) to identify pattern (point source, propagated, mixed)
• Identify time, place, and person characteristics
• Determine index case and source of infection

Step 6: Implement Control Measures

• Non-pharmacological interventions (NPIs):
  • Physical distancing (≥1 metre / 6 feet)
  • Masking (triple-layer surgical or N95 for healthcare workers)
  • Hand hygiene (20-second handwashing with soap, alcohol-based sanitizer)
  • Respiratory etiquette (cover cough/sneeze)
  • Avoid crowding; ensure ventilation
• Pharmacological:
  • COVID-19 vaccines (Covishield, Covaxin, mRNA vaccines)
  • Treatment protocols: Remdesivir (antiviral), Dexamethasone (in severe disease), Oxygen therapy

Step 7: Containment and Mitigation

• Containment phase: Interrupt transmission by isolating cases + quarantining contacts
• Mitigation phase: When spread is too widespread for containment - focus on reducing mortality through healthcare surge capacity
• Lockdowns, travel restrictions, school/workplace closures as needed

Step 8: Communication and Coordination

• Risk communication to the public (counter misinformation)
• Coordination between district/state/national health authorities
• International Health Regulations (IHR) notification to WHO if Public Health Emergency of International Concern (PHEIC)

Step 9: Evaluate and Monitor

• Monitor trends via surveillance dashboards
• Assess effectiveness of control measures
• Adjust interventions based on evidence (Rt monitoring)

Step 10: Recovery and Preparedness

• Health system recovery
• Vaccine scale-up and booster doses
• Strengthen IHR capacities for future outbreaks
• Document lessons learned

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Q6. Hepatitis B (5M)

Definition

Epidemiology

• Global prevalence: ~3.5%; ~257 million with chronic HBV
• Highly endemic (HBsAg ≥8%): sub-Saharan Africa, East Asia
• India: Intermediate endemicity (HBsAg 2-7%)

Transmission Routes

1. Perinatal (mother to child at birth) - most important in high endemic areas
2. Sexual transmission (unprotected sex)
3. Parenteral: contaminated needles (IV drug users), blood transfusions, dialysis
4. Horizontal: Close household contact (shared razors, toothbrushes)

Serological Markers

Clinical Course

• 90% of adults recover completely
• 10% become chronic carriers
• Chronic infection → cirrhosis → hepatocellular carcinoma (HCC)
• Risk of chronic infection is 90% in neonates, 30% in 1-5 year olds, only 5% in adults
• HBV is the 10th leading cause of death worldwide

Prevention

1. Hepatitis B vaccine (recombinant DNA vaccine, 3 doses: 0, 1, 6 months)
   • Universal immunization: birth dose + 2 more doses under UIP
   • HBIG (Hepatitis B Immunoglobulin) for neonates of HBsAg+ mothers (within 12 hours of birth)
2. Safe blood transfusion practices
3. Use of sterile/disposable needles
4. Safe sex practices
5. Universal precautions in healthcare settings

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Q7. Acute Diarrhoeal Disease (5M)

Definition

• Acute watery diarrhoea (<14 days) - most common
• Persistent diarrhoea (≥14 days)
• Dysentery (blood in stool)

Burden

Etiology

Transmission

• Faecal-oral route via contaminated water, food, hands (4 Fs: Faeces, Fingers, Flies, Food/Fluid)

Clinical Features

• Watery stools, vomiting, fever, abdominal cramps
• Dehydration: sunken eyes, dry mouth, loss of skin turgor, decreased urine output
• Severe dehydration → hypovolaemic shock → death

Dehydration Assessment (WHO)

Treatment - ORS (Oral Rehydration Solution)

• ORS is the cornerstone of treatment (WHO/UNICEF low-osmolarity ORS)
• ORS composition: Sodium 75 mmol/L, Chloride 65, Glucose 75, Potassium 20, Citrate 10, Osmolarity 245 mOsm/L
• Zinc supplementation: 20 mg/day for 14 days (children) - reduces severity and duration
• Antibiotics only for dysentery (Cotrimoxazole/Ciprofloxacin) and cholera

Prevention

1. Safe drinking water (boiling, chlorination)
2. Proper sanitation (ODF - Open Defecation Free)
3. Hand hygiene (soap and water - most important)
4. Safe food handling
5. Rotavirus vaccine (under UIP in India)
6. Exclusive breastfeeding for 6 months

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Q8. Leprosy (5M)

Definition and Etiology

Clinical Classification

Ridley-Jopling Classification (based on host immunity):

WHO Classification (for treatment):

• Paucibacillary (PB): 1-5 lesions; smear negative
• Multibacillary (MB): >5 lesions; smear positive

Cardinal Signs of Leprosy

1. Hypopigmented anaesthetic skin patch
2. Thickened peripheral nerves
3. Acid-fast bacilli (AFB) in skin/nasal smear

Diagnosis

• Clinical examination
• Slit-skin smear (AFB)
• Lepromin test (Mitsuda reaction) - indicates host immunity, not active infection

Treatment - MDT (Multi-Drug Therapy)

Prevention

• No vaccine available (BCG gives partial protection)
• Early case detection and MDT treatment
• WHO elimination target: <1 case per 10,000 population (achieved globally in 2000)
• India achieved elimination nationally in 2005

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Q9. Malaria (5M)

Etiology

Life Cycle

• Vector: Female Anopheles mosquito (sexual cycle - sporogony)
• Human: Asexual cycle (schizogony)
  • Exo-erythrocytic (liver stage) → Erythrocytic (RBC stage causing symptoms)

Clinical Features

• Typical attack: Cold stage (rigor, shivering) → Hot stage (high fever 41-42°C) → Sweating stage (profuse sweating, temperature falls)
• Anaemia, splenomegaly in chronic malaria
• P. falciparum complications: Cerebral malaria, blackwater fever, severe anaemia, acute renal failure, hypoglycaemia

Diagnosis

• Gold standard: Peripheral blood smear (thick and thin films)
• Rapid Diagnostic Test (RDT) - HRP-2 antigen for P. falciparum
• PCR

Treatment

• P. vivax: Chloroquine + Primaquine (to eliminate hypnozoites)
• P. falciparum (uncomplicated): ACT - Artemether-Lumefantrine or AS+SP
• Severe malaria: IV Artesunate (drug of choice)

Prevention

• Indoor Residual Spraying (IRS) - DDT, Malathion, Synthetic pyrethroids
• Long-lasting Insecticidal Nets (LLINs)
• Chemoprophylaxis (Chloroquine, Mefloquine for travellers)
• RTS,S/AS01 (Mosquirix) - first malaria vaccine; WHO recommended 2021

National Programme

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Q10. Polio (5M)

Definition and Etiology

Epidemiology

• Only natural host: man
• Transmission: faecal-oral route (primary); droplet spread (secondary)
• Incubation period: 7-14 days (range 3-35 days)
• India: Polio-free since January 13, 2011 (last case: Howrah, West Bengal); certified polio-free on March 27, 2014
• WPV type 2 eradicated (1999); WPV type 3 eradicated (2019); only WPV type 1 remains in Afghanistan and Pakistan

Clinical Forms

1. Inapparent/subclinical (~90-95%) - no symptoms
2. Abortive (~4-8%) - fever, sore throat, GI symptoms; no CNS involvement
3. Non-paralytic/aseptic meningitis (<1%) - meningeal irritation
4. Paralytic (<1%) - flaccid paralysis; types: spinal, bulbar, bulbospinal

Vaccines

• India uses bOPV (bivalent OPV: types 1 and 3) + IPV under UIP

Pulse Polio Immunization (PPI)

• 2 rounds per year on National Immunization Days (NIDs)
• Target: all children under 5 years regardless of previous immunization status
• Mopping-up campaigns in high-risk areas

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Q11. Typhoid (5M)

Etiology

Transmission

• Faecal-oral route via contaminated water and food
• Carriers (especially chronic gallbladder carriers) are the most dangerous source
• "3 Ws" of typhoid control: Water, waste, washbasins (sanitation)

Clinical Features (Widal stages)

• 1st week: Stepladder rising fever, headache, relative bradycardia, constipation
• 2nd week: Sustained high fever (39-40°C), rose spots on abdomen, splenomegaly
• 3rd week: Complications - intestinal perforation, haemorrhage
• 4th week: Defervescence

Diagnosis

• Widal test: Agglutinating antibodies against O (somatic) and H (flagellar) antigens; significant = O titre ≥1:100 in endemic areas
• Blood culture (gold standard in 1st week)
• Bone marrow culture (most sensitive)
• Urine/stool culture (3rd week onwards)
• Typhidot/ELISA (rapid, specific)

Treatment

• Chloramphenicol (first-line historically); now largely replaced by fluoroquinolones
• Ciprofloxacin (adults); Azithromycin (increasing preference for uncomplicated typhoid, resistant strains)
• Ceftriaxone (MDR typhoid, IV)

Prevention

• Safe water supply and sanitation
• Food hygiene; pasteurization of milk
• Typhoid vaccines:
  • Vi polysaccharide vaccine (Typhim Vi) - IM; single dose; >2 years; 70% efficacy; 3-year protection
  • Ty21a (Vivotif) - oral live attenuated; 3 capsules on alternate days; >6 years; 5-year protection

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Q12. Pulmonary Tuberculosis (5M)

Etiology

Transmission

• Airborne via droplet nuclei (<5 µm) from infectious pulmonary TB cases
• Source: sputum-positive (smear-positive) cases
• A smear-positive patient can infect 10-14 new persons per year

Clinical Features

• Symptoms: Chronic cough >2 weeks, haemoptysis, fever, night sweats, weight loss, loss of appetite
• Signs: Dull percussion, bronchial breathing at apex, amphoric breathing in cavitation

Diagnosis

• Sputum AFB smear microscopy (Ziehl-Neelsen staining) - most important; done at DMC (Designated Microscopy Centre)
• GeneXpert/CBNAAT (Cartridge Based Nucleic Acid Amplification Test) - rapid; also detects rifampicin resistance
• Chest X-ray: cavity, infiltrate at apex
• Mantoux/TST: induration ≥10 mm significant; not diagnostic
• Culture on Lowenstein-Jensen medium (gold standard)

Treatment - DOTS (Directly Observed Treatment, Short-course)

• H = Isoniazid, R = Rifampicin, Z = Pyrazinamide, E = Ethambutol, S = Streptomycin

National Programme

• Goal: Eliminate TB by 2025 (5 years ahead of SDG 2030 target)
• Nikshay portal: Case registration and tracking system
• Nikshay Poshan Yojana: Rs. 500/month nutritional support to all TB patients

Prevention

• BCG vaccine: Live attenuated M. bovis; given at birth; 50-80% protection against severe childhood TB; does NOT prevent pulmonary TB in adults
• DOTS and contact tracing
• Improving housing, nutrition and ventilation

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Q13. STDs (Sexually Transmitted Diseases) (5M)

Definition

Classification

Key STDs

Syphilis

• Caused by Treponema pallidum; incubation 9-90 days
• Primary: painless chancre + regional lymphadenopathy
• Secondary: maculopapular rash on palms and soles, condylomata lata
• Tertiary: gumma, cardiovascular syphilis, neurosyphilis
• Congenital syphilis: saddle nose, Hutchinson's teeth, interstitial keratitis
• Treatment: Benzathine Penicillin G (single IM dose for primary/secondary)

Gonorrhoea

• Caused by Neisseria gonorrhoeae (gram-negative diplococcus)
• Males: urethritis with purulent discharge; Females: often asymptomatic
• Complications: PID, ectopic pregnancy, infertility; ophthalmia neonatorum
• Treatment: Ceftriaxone (drug of choice; increasing resistance to fluoroquinolones)

HIV/AIDS (see Lab Investigations of HIV below)

Prevention of STDs

1. ABC approach: Abstinence, Be faithful, Condom use
2. Free distribution of condoms (NACO programme)
3. Treatment of STIs (reduces HIV transmission)
4. Syndromic case management (most practical in resource-limited settings)
5. Voluntary Counselling and Testing (VCT)
6. Prevention of Parent to Child Transmission (PPTCT) programme
7. HPV vaccine (Gardasil/Cervarix) - prevents cervical cancer

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Q14. Water-Borne Diseases (5M)

Definition

Important Water-Borne Diseases

Common Epidemic Clues

• Point source water-borne epidemic: Explosive onset, attack rate highest near contaminated source, subsides once source is removed
• Continuous water-borne epidemic: Gradual onset, affects all areas served by contaminated supply

Water Quality Standards (India)

• Acceptable turbidity: <1 NTU
• Residual chlorine at consumer end: 0.2 mg/L
• Coliform count: zero in treated piped supply
• MPN (Most Probable Number) test for coliforms

Prevention

1. Water treatment: Chlorination, boiling, filtration (most important)
2. Safe storage of drinking water
3. Sanitary disposal of human excreta (toilets)
4. Protection of water sources (dug wells, hand pumps)
5. Hygiene education
6. Surveillance of water quality

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Q15. Food-Borne Diseases (5M)

Definition

Classification

Food-Borne Infections

• Organism ingested with food → multiplies in gut → causes disease
• Examples: Salmonella, Shigella, ETEC, Campylobacter, hepatitis A, Listeria

Food-Borne Intoxications (True Food Poisoning)

• Preformed toxin in food ingested (no need for live bacteria)
• Examples: Staphylococcus aureus (toxin formed in food at room temperature), Clostridium botulinum (botulinum toxin in canned/tinned food), Bacillus cereus

Major Food Poisoning Types

Investigation of Food Poisoning Outbreak

1. Confirm the diagnosis (clinical + lab)
2. Define a case
3. Collect food histories from cases and controls
4. Identify the vehicle food and source
5. Collect food, stool, vomitus, blood samples for culture
6. Inspect food handling premises
7. Calculate attack rates by food item (food-specific attack rate)

Prevention

1. Safe food preparation (cook to proper temperature)
2. Proper refrigeration (<5°C) and hot holding (>60°C)
3. Avoid cross-contamination (raw vs cooked)
4. Personal hygiene of food handlers (handwashing, health checks)
5. FSSAI (Food Safety and Standards Authority of India) standards

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Q16. Post-Exposure Rabies Prophylaxis (3M)

Background

Animal Bite Categories (WHO)

PEP Protocol

1. Wound Management (First and most important step)

• Immediately and thoroughly wash wound with soap and water for 15 minutes
• Flush with water; apply povidone-iodine or 70% alcohol
• Do NOT suture the wound immediately

2. Rabies Vaccine

• Cell culture vaccines (CCV) - purified chick embryo cell vaccine (PCECV), human diploid cell vaccine (HDCV), Purified Vero Cell Rabies Vaccine (PVRV)
• Essen regimen (5-dose IM): Days 0, 3, 7, 14, 28 (at deltoid)
• Zagreb regimen (2-1-1): 2 doses on day 0 (both deltoids) + 1 dose on day 7 + 1 dose on day 21

3. Rabies Immunoglobulin (RIG) - Only for Category III

• Human RIG (HRIG): 20 IU/kg body weight
• Equine RIG (ERIG): 40 IU/kg
• Infiltrate maximum possible dose around and into the wound; remaining dose given IM at a site different from vaccine
• Must be given on day 0 only (before or simultaneously with first vaccine dose)

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Q17. Lab Investigations of HIV (3M)

Overview

Laboratory Tests

A. Serological Tests (Antibody-based)

B. Antigen Detection

C. Nucleic Acid Tests (NAT/NAAT)

NACO Testing Algorithm (India - 3 test serial algorithm)

• A1 (ELISA/Rapid) - if reactive:
• A2 (different ELISA/Rapid) - if reactive:
• A3 (third different assay) - if reactive = HIV positive
• If A1 reactive + A2 non-reactive = indeterminate (repeat in 2-4 weeks)

Window Period

• 3-12 weeks (antibodies usually appear by 6 weeks)
• 4th generation tests reduce window period to ~18 days

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Q18. Homoeopathic Prophylaxis for Japanese Encephalitis (3M)

Japanese Encephalitis - Background

• Viral encephalitis caused by JE virus (Flavivirus)
• Vector: Culex tritaeniorhynchus; Reservoir: pigs and wading birds
• Vaccine of choice: SA 14-14-2 live attenuated vaccine (given in India under UIP)

Homoeopathic Prophylaxis

Evidence from India

• Large-scale use in UP (reported by Dr. B. K. Srinivasan and others) showed reduction in JE incidence in areas where Belladonna 200C was administered
• The protocol involves administering Belladonna 200C (4 globules per child) at 2-week intervals during the JE season
• Critics note the lack of RCT evidence; proponents cite observational data from mass campaigns in UP

Scientific Standing

• Not recognized as a replacement for JE vaccine by WHO, ICMR, or Government of India as primary prevention
• Used as adjunct/supplementary prophylaxis in areas where vaccine coverage is inadequate
• Included in K. Park as a point of discussion in the context of alternative preventive measures for JE in India

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Q19. Cholera Control (3M)

Causative Agent

Epidemiology

• Transmission: Contaminated water and food (faecal-oral)
• Incubation: Few hours to 5 days
• Clinical: "Rice-water stools", profuse watery diarrhoea without fever, severe dehydration
• Case fatality without treatment: 25-50%; with treatment: <1%

Cholera Control Measures

1. Case Management

• ORS for mild-moderate dehydration; IV Ringer's Lactate for severe dehydration
• Antibiotics reduce duration and excretion: Doxycycline (single dose 300mg; drug of choice), Tetracycline, Cotrimoxazole

2. Water Control

• Emergency chlorination of water supply (residual chlorine 0.5 mg/L)
• Boiling of drinking water
• Source protection

3. Sanitation

• Proper disposal of faeces and vomitus (disinfect with bleaching powder)
• Safe disposal of human excreta
• Fly control

4. Contact Tracing

• Identification of secondary cases in household
• Chemoprophylaxis for contacts with Doxycycline

5. Food Control

• Avoid uncooked food, shellfish
• Supervision of food handlers

6. Vaccination

• Oral Cholera Vaccine (OCV): Dukoral (WC-rBS), Shanchol; 2 doses
• WHO recommends OCV for endemic areas and outbreak control alongside WASH measures
• Parenteral cholera vaccine: NOT recommended (poor efficacy)

7. Notification

• Cholera is a notifiable disease under IHR 2005 (no longer compulsory notification to WHO as of IHR 2005 - only if constitutes PHEIC)

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Q20. Anti-Larval Control Measures (3M)

Purpose

Methods

1. Source Reduction (Environmental Control) - MOST IMPORTANT

• Eliminate stagnant water and breeding sites
• Drain waterlogged areas; fill pits and depressions
• Proper disposal of tyres, cans, flower pots, coolers
• Regular cleaning and scrubbing of water storage containers
• Roof gutters kept clear; inverted stacking of empty containers

2. Chemical Larvicides

• Temephos (Abate): 1 ppm effective; safe for drinking water; used in domestic water containers; WHO-approved
• Malathion emulsifiable concentrate: Applied to breeding sites
• Petroleum oils: Spread over stagnant water surfaces - suffocates larvae

3. Biological Control

• Gambusia affinis (mosquitofish): Voracious larval feeder; introduced into wells, ponds, rice fields - most widely used biological control
• Bacillus thuringiensis var. israelensis (Bti): Bacterial toxin; highly specific to mosquito larvae; no environmental harm
• Bacillus sphaericus: Effective against Culex; especially in polluted water
• Copepods (Mesocyclops): Predatory crustaceans; used in large water bodies

4. Polystyrene Beads

• Float on water surface in latrines; prevent mosquito breeding in pit latrines by blocking access of egg-laying females

5. Legislation

• Anti-mosquito bylaws under Prevention of Mosquito Breeding Act; penalty for maintaining stagnant water on premises

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Q21. Q Fever (3M)

Definition and Etiology

Reservoir and Transmission

• Reservoir: Sheep, cattle, goats (primary); cats, dogs, birds
• Animals shed Coxiella in urine, faeces, milk, birth products (amniotic fluid - very high concentration)
• Transmission to humans:
  • Inhalation of contaminated aerosols (most common - dried birth products, manure, soil)
  • Contact with infected animals
  • Ingestion of contaminated milk (raw milk)
  • Multiple routes: water-borne, food-borne, tick-borne, person-to-person (rare)
• Q fever is not transmitted by tick bite to humans routinely (unlike other rickettsioses)

Clinical Features

• Acute Q fever: Self-limiting febrile illness; pneumonia ("Q fever pneumonia"); hepatitis
• Chronic Q fever: Endocarditis (most serious; occurs mainly in patients with valvular heart disease), hepatitis, osteomyelitis
• Incubation: 2-4 weeks
• Occupational risk: Abattoir workers, farmers, veterinarians, laboratory workers

Diagnosis

• Serology: Complement fixation test (CFT); ELISA; IFA (Indirect Fluorescent Antibody)
• Phase I antigen for chronic; Phase II for acute

Treatment

• Acute: Doxycycline (drug of choice)
• Chronic (endocarditis): Doxycycline + Hydroxychloroquine (long-term, 18+ months)

Prevention

• Proper disposal of birth products from animals
• Pasteurization of milk
• Q fever vaccine available for high-risk occupational groups (Australia - Q-VAX)

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Q22. Congenital Rubella Syndrome (CRS) (3M)

Rubella Background

Congenital Rubella Syndrome (CRS)

Risk of CRS by Trimester

• 1st trimester: 85% risk of CRS
• 2nd trimester: 10-20% risk
• After 20 weeks: Risk very low

Classical Triad of CRS (Gregg's Triad)

1. Cataract (and other eye defects: microphthalmia, glaucoma)
2. Congenital heart disease (Patent Ductus Arteriosus, pulmonary artery stenosis, VSD)
3. Sensorineural deafness (most common single defect)

Expanded CRS (Other Features)

• Microcephaly, intellectual disability
• "Blueberry muffin" rash (dermal erythropoiesis)
• Thrombocytopenic purpura, hepatosplenomegaly
• Low birth weight, growth retardation

Diagnosis

• Rubella IgM in infant (or mother)
• Virus isolation from throat swab, urine, CSF
• Haemagglutination Inhibition (HI) test (four-fold rise in titre)

Prevention

• MMR vaccine (Measles-Mumps-Rubella) - live attenuated vaccine
  • 2 doses: At 9-12 months and 15-18 months (under UIP India)
  • Key rule: Do NOT give to pregnant women; vaccinate women of child-bearing age and advise to avoid pregnancy for 1 month after vaccination
• Screen women of reproductive age for rubella immunity before pregnancy
• If non-immune, vaccinate before pregnancy

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Q23. Food Poisoning (3M)

Definition

1. Living pathogenic microorganisms (food-borne infection), or
2. Poisonous toxins produced by microorganisms (food intoxication), or
3. Chemicals (chemical food poisoning)

Classification and Key Features

Investigation of an Outbreak

1. Identify cases and define case definition
2. Food-specific attack rates: Compare illness rates among those who ate vs. did not eat each food item - the food with highest attack rate in eaters + lowest in non-eaters is the suspect vehicle
3. Collect food, stool, vomitus samples for culture
4. Inspect food handling premises and identify the source of contamination
5. Notify to health authorities

Treatment

• Supportive: Rehydration (ORS/IV fluids)
• Antibiotics generally NOT recommended for self-limiting food poisoning
• Exception: Botulism - antitoxin + ICU support; Salmonella with bacteraemia - ciprofloxacin

Prevention

• Cook food thoroughly; avoid cross-contamination
• Refrigerate perishables promptly (below 5°C)
• FSSAI regulations for food safety in India
• Health examination of food handlers; exclude those with skin infections, diarrhoea

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• For 10M answers: Write an introduction, epidemiology, etiology, clinical features, diagnosis, treatment, prevention/control
• For 5M answers: Cover etiology, key clinical features, diagnosis, treatment, prevention
• For 3M answers: 2-3 key points per topic, focus on what's most distinctive

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UNIT 3: ENVIRONMENTAL HEALTH

Complete Exam Answers (Based on K. Park)

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Q1. Air Pollution (10M)

Definition

Classification of Air Pollutants

By Origin

• Primary air pollutants: Emitted directly from a source (factory chimney, exhaust pipe). Can be measured at source. Examples: SO₂, CO, soot, smoke
• Secondary air pollutants: Formed within the atmosphere by chemical reactions of primary pollutants with atmospheric components (O₂, water). Cannot be included directly in emission inventories. Example: Ozone (formed from photochemical reactions of NOₓ + VOCs in sunlight)

By Physical State

• Gaseous pollutants: Present as gases or vapours; individual molecules; pass through filters. Water-soluble ones deposit in upper respiratory tract; insoluble ones penetrate deep lung
• Particulate pollutants: Solid or liquid particles suspended in air; range from 1-100 µm in diameter; "respirable dust" = particles <5 µm that penetrate alveoli

Sources of Air Pollution

A. Outdoor (Ambient) Air Pollution

1. Industries and factories - burning of fossil fuels, smelters, refineries (SO₂, NOₓ, particulates)
2. Motor vehicles - automobile exhaust (CO, hydrocarbons, NOₓ, lead from leaded petrol, PM2.5)
3. Power plants - coal/oil combustion (SO₂, fly ash, heavy metals)
4. Natural sources - volcanic eruptions, forest fires, pollen, dust storms

B. Indoor Air Pollution

1. Combustion - burning of biomass fuels (wood, cow dung, crop residues), coal, kerosene in poorly ventilated homes - the single largest source in developing countries
2. Tobacco smoke (Environmental Tobacco Smoke/ETS) - contains >4,000 chemicals including CO, formaldehyde, PAHs, benzene
3. Building materials - Radon (from granite/soil beneath buildings); formaldehyde from particleboard/plywood; asbestos
4. Volatile Organic Compounds (VOCs) - from paints, adhesives, cleaning products, aerosol sprays
5. Biological contaminants - mould, fungi, dust mites, cockroach allergens, animal dander in poorly ventilated humid spaces

• Acute respiratory infections (especially in children)
• Chronic obstructive pulmonary disease (COPD)
• Lung cancer (biomass smoke)
• WHO estimates ~4 million premature deaths per year due to household air pollution

Major Outdoor Air Pollutants and Effects

Health Effects of Air Pollution

Immediate Effects

• Acute bronchitis, exacerbation of asthma and COPD
• Irritation of eyes, nose, throat
• London Smog Disaster (1952): 4,000+ excess deaths in 4 days due to combination of SO₂, smoke, temperature inversion - classic example of acute air pollution episode

Delayed/Chronic Effects

• Chronic bronchitis, emphysema, COPD
• Lung cancer (PAHs, hydrocarbons, PM)
• Bronchial asthma, respiratory allergies
• Cardiovascular disease (PM2.5 promotes atherosclerosis)
• Lead neurotoxicity in children (IQ loss, behavioural problems)

Environmental Effects

• Acid rain: SO₂ + NOₓ → H₂SO₄ + HNO₃; damages forests, aquatic ecosystems, buildings
• Greenhouse effect: CO₂, methane, N₂O trap heat → global warming → climate change
• Ozone depletion (stratospheric): CFCs destroy stratospheric ozone → increased UV-B → skin cancer, cataracts

Monitoring of Air Pollution

• SPM (Suspended Particulate Matter) - measured by high volume sampler
• RSPM/PM10 - respirable suspended particulates
• PM2.5 - fine particles most harmful to health
• SO₂, NOₓ, CO levels - by electro-chemical analysers
• National Ambient Air Quality Standards (NAAQS) set by CPCB (Central Pollution Control Board)

Control of Air Pollution

Source Control (Most Important)

1. Fuel substitution - shift from coal/biomass to cleaner fuels (LPG, PNG, CNG, electricity)
2. Emission standards - Bharat Stage (BS-VI) norms for vehicles; stack emission standards for industries
3. Process modification - cleaner production technologies, catalytic converters in vehicles
4. Relocation of industries away from populated areas

Pollution Abatement at Source

1. Arresters/filters - cyclone separators, bag filters, electrostatic precipitators for particulate removal
2. Scrubbers - wet scrubbers for SO₂ and acid gases
3. Catalytic converters - oxidize CO and hydrocarbons in vehicle exhaust

Regulatory Measures

• Air (Prevention and Control of Pollution) Act, 1981 (India)
• Environment (Protection) Act, 1986
• Vehicle emission testing and PUC certificates
• Industrial licensing and pollution control norms by CPCB/SPCBs

Community Measures

• Urban greening/tree plantation (trees act as carbon sinks and particulate filters)
• Promotion of public transport
• Ban on stubble burning
• National Clean Air Programme (NCAP) 2019 - target 20-30% reduction in PM2.5 by 2024

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Q2. Purification of Water on a Large Scale (10M)

Introduction

Sources of Water

1. Surface water - rivers, lakes, reservoirs (highest contamination, requires full treatment)
2. Ground water - wells, tube wells, springs (generally cleaner, may need chemical treatment)
3. Rain water - relatively clean but limited quantity

Characteristics of Safe Drinking Water (WHO/BIS Standards)

• Colourless, odourless, tasteless
• Turbidity: <1 NTU (acceptable); <5 NTU (maximum permissible)
• pH: 6.5-8.5
• Total dissolved solids: <500 mg/L (acceptable)
• Zero coliforms in treated piped supply
• Residual chlorine: ≥0.2 mg/L at consumer tap

Steps in Large-Scale Water Purification

STEP 1: STORAGE (Pre-treatment/Reservoir)

• Raw water stored in large impounding reservoirs for weeks to months
• Results in natural purification: sedimentation of suspended matter, death of bacteria (by sunlight, starvation, competition), algal blooms that consume bacteria
• 90% bacterial reduction can occur with storage alone
• Limitation: Slow, unreliable; not sufficient as sole measure

STEP 2: SEDIMENTATION

• Raw water allowed to stand in large tanks (sedimentation basins/clarifiers)
• Suspended particles settle under gravity
• Plain sedimentation: Removes particles >0.1 mm in 4-8 hours; reduces turbidity by 70-80%
• Particles <0.1 mm (colloidal) remain suspended - require coagulation

STEP 3: COAGULATION (Sedimentation with Coagulation)

• Chemical coagulants added to remove colloidal particles:
  • Alum (aluminium sulphate) - most widely used; dose 5-40 mg/L
  • Ferrous sulphate + lime (less common)
  • Polyaluminium chloride (PAC)
• Alum reacts with bicarbonates in water → aluminium hydroxide floc (gelatinous precipitate) - has enormous surface area that adsorbs colloidal particles, bacteria, viruses, and colour
• Flocculation = gentle stirring to enhance particle collision and floc growth
• Rapid mix (1-2 min) followed by slow mix (20-40 min) in a flocculation tank
• Floc settles in sedimentation basin (clarifier)
• Removes 99% of turbidity, significant reduction in bacteria and viruses

STEP 4: FILTRATION

• Passes water through a bed of filter medium (sand + gravel) to remove remaining particles, floc, and microorganisms

• Sand grain size: 0.2-0.4 mm; bed depth: 90-120 cm; flow rate: 0.1-0.4 m³/m²/hour (slow)
• Biological purification by Schmutzdecke (biological layer on sand surface) - a mat of algae, protozoa, bacteria that remove pathogens, iron, manganese
• Removes 98-99.9% of bacteria; also removes protozoa (Giardia, Cryptosporidium)
• Advantages: Simple, effective, no chemicals needed except for final chlorination; long runs (1-3 months before cleaning)
• Disadvantages: Requires large land area; ineffective with highly turbid water; slow output; cold weather inhibits biological activity
• Must be cleaned by scraping (not backwashing - would destroy Schmutzdecke)

• Sand grain size: 0.4-1.2 mm; bed depth: 60-75 cm; flow rate: 5-15 m³/m²/hour (50-100x faster than SSF)
• Requires prior coagulation/sedimentation
• Mechanical filtration only (no biological layer)
• Removes 98-99% of bacteria when combined with coagulation
• Advantages: Requires less land area; higher throughput; handles turbid water; cleaned by backwashing
• Disadvantages: Requires chemicals; needs skilled operators; more expensive

• Water forced through filter under pressure
• Used for smaller supplies; same principle as rapid sand filter

STEP 5: DISINFECTION

• Chlorine is the most widely used disinfectant worldwide
• Forms: Chlorine gas (Cl₂), bleaching powder (Ca(OCl)Cl, contains 33% available chlorine), liquid sodium hypochlorite (NaOCl), HTH (High Test Hypochlorite, 60-70% available chlorine)
• Mechanism: Chlorine + water → Hypochlorous acid (HOCl) + HCl. HOCl is the active germicidal form
• Residual chlorine requirement: 0.2 mg/L at consumer's tap (free residual after 30 min contact time at pH <8)
• Chlorine demand = Total chlorine applied - Residual chlorine remaining
• Break-point chlorination: Adding chlorine until all organics and ammonia are oxidized; further addition gives free residual chlorine. Break point = point of minimum residual after which free residual rises

• Chlorination applied at two stages: once at inlet, once before distribution
• Used for large municipal supplies

• Very high dose of chlorine (10-20x normal) added → 100% kill of pathogens
• Excess chlorine removed by sodium thiosulphate or activated carbon
• Used in emergencies, polluted water

• Chlorine + ammonia → Chloramines (monochloramine)
• Provides more persistent residual in distribution system
• Does not produce trihalomethanes (THMs) unlike free chlorine
• Less effective against viruses than free chlorine

• Ozone (O₃) is the most powerful disinfectant; excellent against viruses, Giardia, Cryptosporidium
• Does NOT leave residual in distribution system - requires secondary chlorination
• Expensive; used in developed countries

• UV light (254 nm) damages DNA of microorganisms
• Effective against bacteria, viruses, protozoa including Cryptosporidium
• No residual effect; clear water required; used in point-of-use systems

STEP 6: OTHER TREATMENTS (as needed)

• Aeration - removes dissolved gases (CO₂, H₂S), oxidizes iron and manganese
• Fluoridation - addition of fluoride to 0.5-1.0 mg/L to prevent dental caries (defluoridation if naturally >1.5 mg/L - Nalgonda technique)
• Softening - removal of hardness (Ca²⁺, Mg²⁺) by lime-soda or zeolite process
• Iron/Manganese removal - by aeration + filtration

Summary Flow Diagram

Raw Surface Water
     ↓
Reservoir Storage (natural purification)
     ↓
Coagulation + Flocculation (alum addition)
     ↓
Sedimentation (clarifier)
     ↓
Filtration (slow or rapid sand filter)
     ↓
Disinfection (chlorination)
     ↓
Storage in clear water reservoir
     ↓
Distribution to consumers

Quality Control

• Regular bacteriological testing: MPN (Most Probable Number) test using Presumptive, Confirmed, and Completed tests
• E. coli = indicator of faecal contamination; should be zero in treated supply
• Residual chlorine testing: OTO (ortho-tolidine) test at distribution points

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Q3. Occupational Hazards (5M)

Definition

1. Physical Hazards

• Direct effects of excess heat: heat hyperpyrexia, heat exhaustion, heat syncope, heat cramps, burns
• Industries at risk: foundry, glass, steel, deep mines (Kolar Gold Fields - 65°C at 11,000 feet depth)
• Cold injuries: chilblains, trench foot, frostbite, general hypothermia
• Comfort zone in India: 20-27°C (corrected effective temperature 69-80°F)

• Poor illumination: eye strain, headache, lachrymation, miner's nystagmus (chronic)
• Excess glare: visual fatigue, accidents

• Auditory effects: temporary or permanent sensorineural hearing loss (Occupational Deafness - noise >85 dB over 8 hours)
• Non-auditory effects: fatigue, irritability, hypertension, decreased efficiency, anxiety

• Pneumatic drills, hammers
• "White finger" (Vibration White Finger) = Raynaud's phenomenon; joint damage in hands, elbows, shoulders

• Arc welding: photokeratitis ("welder's flash") - intense conjunctivitis and keratitis; recovers in a few days

• X-ray workers, nuclear industry
• Effects: cancer, leukaemia, aplastic anaemia, genetic mutations, sterility, cataracts
• Maximum permissible occupational exposure: 5 rem/year (whole body) per ICRP

• Deep sea divers, caisson workers: Caisson disease (decompression sickness / "the bends") - N₂ bubbles in blood; joint pain, paralysis, death
• Coal miners: barotrauma

2. Chemical Hazards

• "Respirable dust" = particles <5 µm that reach alveoli
• Silicosis (silica dust) - quarry, mining, sandblasting; most dangerous; may develop TB (silicotuberculosis)
• Anthracosis (coal dust) - coal miners
• Asbestosis (asbestos) - shipbuilding, insulation; also causes mesothelioma and lung cancer
• Byssinosis (cotton dust) - textile workers
• Siderosis (iron dust) - foundry workers
• Bagassosis (sugar cane residue dust)

• CO: incomplete combustion - garage workers, mines; forms COHb
• Lead: battery manufacture, smelting - encephalopathy, anaemia, colic
• Mercury: fluorescent lamp, chlor-alkali - tremors, gingivitis, neuropsychiatric changes ("Mad Hatter's disease")
• Benzene: rubber industry - aplastic anaemia, leukaemia

3. Biological Hazards

• Anthrax - hide and wool workers
• Brucellosis - veterinarians, slaughterhouse workers
• Leptospirosis - sewer workers, farmers
• Q fever - slaughterhouse workers, veterinarians
• HIV, Hepatitis B/C - healthcare workers (needlestick injuries)
• Zoonoses - farmers, veterinarians

4. Mechanical Hazards

• Moving machinery parts, protruding objects
• ~10% of industrial accidents due to mechanical causes
• Injuries ranging from lacerations to amputations and crush injuries

5. Psychosocial Hazards

• Frustration, lack of job satisfaction, insecurity, poor human relationships
• Health effects: Anxiety, depression, alcoholism, sickness absenteeism, peptic ulcer, hypertension, coronary heart disease

Prevention of Occupational Hazards

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Q4. Sanitation in Fairs and Festivals (5M)

Introduction

Health Risks at Fairs and Festivals

1. Water-borne diseases - cholera, typhoid, hepatitis A, dysentery (from contaminated water/food)
2. Food-borne diseases - from improperly handled food by temporary vendors
3. Overcrowding - facilitates spread of respiratory infections, measles, meningitis
4. Stampede and trauma - crowd management failures
5. Vector breeding - accumulated garbage, stagnant water
6. Environmental pollution - open defecation, garbage

Sanitation Measures Required

1. Water Supply

• Adequate safe drinking water (minimum 5 litres/person/day for drinking; 15-20 L/person/day for all purposes)
• Temporary water supply points (tankers, standpipes)
• Chlorination of water at source (residual chlorine 0.2 mg/L at tap)
• Regular bacteriological testing of water supply

2. Excreta Disposal

• Provision of adequate number of temporary latrines:
  • 1 toilet seat per 25 females and 1 per 40-50 males (or as per Sphere standards: 1 per 20 persons for emergencies)
  • Separate latrines for males and females
  • Properly sited away from water sources (minimum 30 metres)
• Trench latrines (1 foot wide × 3-4 feet deep) for temporary use
• Adequate signage to direct people to latrines
• Regular cleaning and disinfection (bleaching powder in latrines)

3. Waste Disposal

• Adequate number of bins/receptacles at short intervals
• Regular collection and disposal (minimum twice daily)
• Burning or burying of refuse at designated spots away from food stalls and water sources
• Prevention of open dumping near the venue

4. Food Safety

• Registration/licensing of food vendors
• Inspection of food quality and hygiene
• Ban on high-risk foods (cut fruits, pre-cooked uncovered foods, raw shellfish)
• Safe food handling: covered food, clean utensils, handwashing facilities at food stalls
• Availability of clean water for food vendors

5. Drainage

• Proper drainage to prevent waterlogging and stagnant water (mosquito breeding)
• Temporary drainage channels around the fair ground

6. Vector Control

• Pre-event anti-larval measures (fogging, source reduction)
• Anti-fly measures (covering garbage, use of insecticides)
• Rodent control

7. Medical Services

• First aid posts at regular intervals
• Ambulance services
• Referral arrangements with nearest hospital
• Surveillance for disease outbreaks (daily reporting by medical posts)
• Adequate stock of ORS for diarrhoea cases

8. Health Education

• Announcements about hygiene and sanitation
• Information about locations of latrines, water points, medical posts

9. Pre-Event Planning

• Site inspection and sanitary survey before the event
• Inter-departmental coordination (Health, PWD, Police, Revenue)
• Allocation of adequate budget for sanitation
• Appointment of sanitary inspector for continuous monitoring

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Q5. Biomedical Waste (5M)

Definition

Sources of Biomedical Waste

1. Hospitals, nursing homes, clinics
2. Blood banks, laboratories
3. Veterinary institutions
4. Research laboratories and institutions
5. Animal houses

Types of Biomedical Waste (BMW Rules 2016 - 4 Categories)

Composition of Hospital Waste

• General/non-hazardous waste: 85% (similar to municipal solid waste - paper, food, packaging)
• Hazardous/biomedical waste: 15%
  • Infectious: 10%
  • Sharps: 1%
  • Pathological: 1%
  • Other hazardous: 3%

Methods of Treatment/Disposal

1. Incineration

• High-temperature combustion at 850-1000°C (two-stage); completely destroys pathogens
• Used for anatomical waste, chemotherapy waste, animal carcasses
• Disadvantage: Air pollution if not properly equipped (dioxins, furans); not suitable for all BMW

2. Autoclaving (Steam Sterilization)

• 121°C at 15 psi for 30-60 minutes - kills all vegetative bacteria, most spores, viruses
• Suitable for microbiology waste, sharps, red bag waste
• After autoclaving: waste can be disposed as municipal solid waste or sent for recycling

3. Microwaving

• Microwave irradiation at 2,450 MHz; generates heat throughout waste material
• Equivalent effectiveness to autoclaving; more energy efficient
• Not suitable for anatomical or radioactive waste

4. Chemical Disinfection

• Sodium hypochlorite (1% for liquid waste), glutaraldehyde, formaldehyde
• For liquid waste, blood spills, microbiological waste

5. Secure Landfill/Deep Burial

• For non-infectious, non-sharps, non-incinerable waste in low-resource settings
• Waste buried at >2 m depth; fenced area; lined pit

6. Shredding/Mutilation

• Sharps, glass, plastic - shredded/mutilated after decontamination to prevent reuse

Common Biomedical Waste Treatment Facilities (CBMWTFs)

• Under BMW Rules 2016, every healthcare facility generating >10 kg BMW/day must either:
  • Set up own treatment facility, OR
  • Use a Common Biomedical Waste Treatment Facility (CBMWTF)

Legislation

• Biomedical Waste (Management and Handling) Rules, 1998 - notified under Environment Protection Act 1986
• Revised as BMW Management Rules 2016 - 4-colour coding system introduced
• CPCB and SPCBs are regulatory authorities

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Q6. Solid Waste Disposal (5M)

Definition

Composition of Municipal Solid Waste (India)

• Organic matter/food waste: 40-60%
• Paper: 5-10%
• Plastics: 5-10%
• Glass, metals: 2-5%
• Inert matter (soil, stones): 20-30%

Methods of Solid Waste Disposal

1. Open Dumping (Not Recommended)

• Simply depositing waste in open low-lying areas
• Problems: Attracts flies, rodents, vectors; leachate contaminates groundwater; air pollution from fires; eye-sore
• Still the most common method in developing countries

2. Sanitary Landfill (Controlled Tipping)

• Best practical method for large quantities of waste
• Waste deposited in carefully planned engineered sites:
  • Trench method: Trench dug, waste deposited, covered with earth daily (cover: 15-23 cm daily; 60-90 cm weekly)
  • Area method: Waste spread on natural ground, compacted, covered with earth
  • Ramp method: Combination of above
• Lined with impermeable membrane; leachate collection system; gas venting (methane)
• Site must be away from water sources, habitation
• Advantages: Large volumes; no air pollution; land reclaimed after 5-10 years
• Limitations: Requires large land area; methane generation; not suitable near airports (bird hazard)

3. Incineration

• Controlled burning at high temperatures (850-1000°C)
• Reduces volume by 85-95%; destroys pathogens completely
• Advantages: Suitable for pathological, pharmaceutical waste; recovers energy (waste-to-energy)
• Disadvantages: Expensive; air pollution (dioxins, furans if inadequate temperature); not suitable for wet waste (common in India)

4. Composting

• Controlled biological decomposition of organic matter by microorganisms
• Produces humus (compost) - an excellent soil conditioner and fertilizer
• Two methods:
  • Windrow composting: Waste spread in long rows (windrows), turned periodically; takes 4-6 weeks
  • Mechanical composting (Bangalore method): Rapid composting in mechanical digesters; 1-2 weeks
• Ideal for India: High organic content of municipal waste; product has market value

5. Vermicomposting

• Use of earthworms (Eisenia foetida) to convert organic waste into vermicompost
• High-quality fertilizer; rapid decomposition; low odour

6. Biogas/Anaerobic Digestion

• Organic waste in sealed chambers → biogas (methane + CO₂) + digestate (fertilizer)
• Dual benefit: energy + fertilizer

7. Pyrolysis

• Thermal decomposition in absence of oxygen; produces syn-gas, oil, and char
• Used for plastics, rubber (tyres)

8. Recycling (3Rs: Reduce, Reuse, Recycle)

• Segregation at source → dry waste (paper, plastic, metal, glass) → recycled
• Wet/organic waste → composted or biogas

Waste Segregation (Swachh Bharat Mission)

• Dry waste: Recyclable materials
• Wet waste: Organic, food, kitchen waste
• Hazardous waste: Batteries, chemicals, paints
• Domestic hazardous: Sanitary waste, medicines

Legislation

• Solid Waste Management Rules 2016 (notified under EPA 1986)
• Swachh Bharat Mission (SBM-Urban): Target ODF+ status; scientific solid waste management

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Q7. Radiation Effects (5M)

Types of Radiation

A. Ionizing Radiation

• Alpha (α) particles - heavy, short range; blocked by paper/skin; most dangerous if inhaled/ingested (internal emitters like radon)
• Beta (β) particles - electrons; blocked by 1-2 cm of plastic; can penetrate superficial skin
• Gamma (γ) rays - electromagnetic radiation; most penetrating; require thick lead/concrete shielding; used in diagnostic and therapeutic radiology
• X-rays - similar to gamma; artificially produced; used in diagnosis
• Neutrons - produced in nuclear reactors; very penetrating

• Natural background (radon, cosmic rays, soil)
• Medical: X-rays, nuclear medicine (⁹⁹mTc, ¹³¹I)
• Industrial: Cobalt-60 (industrial radiography), nuclear power plants
• Nuclear weapons

B. Non-Ionizing Radiation

• UV radiation, infrared, visible light, microwaves, radiofrequency

Units of Radiation

Deterministic vs. Stochastic Effects

Health Effects of Ionizing Radiation

1. Acute Radiation Syndrome (ARS)

• Haematopoietic syndrome (1-6 Gy): Bone marrow suppression → pancytopenia → infections and bleeding; 50% mortality (LD₅₀ = ~3-4 Gy without treatment)
• Gastrointestinal syndrome (6-30 Gy): GI epithelium destruction → bloody diarrhoea, dehydration, infection; nearly 100% fatal
• Cerebrovascular syndrome (>30 Gy): Rapid onset brain oedema; death within hours-days

2. Long-Term (Stochastic) Effects

• Leukaemia: Appears 5-10 years after exposure (AML, CML most common)
• Solid tumours: Thyroid (especially in children exposed to radioiodine), lung, breast, liver
• Genetic effects: Mutations in germ cells → hereditary disorders in offspring
• Hiroshima and Nagasaki atomic bomb survivors: Landmark evidence for cancer risk

3. Specific Occupational Effects

• Cataracts: Lens especially sensitive (crystalline lens); occurs after chronic exposure (>2 Gy)
• Aplastic anaemia: Bone marrow suppression; classic occupational hazard of early radiologists (pre-safety era)
• Skin damage: Erythema, epilation (hair loss), necrosis, radiodermatitis
• Sterility: Testes and ovaries sensitive; temporary/permanent depending on dose

4. Radon-Associated Lung Cancer

• Radon gas (²²²Rn) - naturally occurring; accumulates in poorly ventilated buildings
• Second leading cause of lung cancer after smoking; especially hazardous to uranium miners

Non-Ionizing Radiation Effects

• UV radiation: Erythema (sunburn), photokeratitis, photoageing, skin cancer (squamous cell, basal cell, melanoma), cataracts
• Infrared: Retinal damage, cataracts (glass blowers), skin burns
• Microwave/RF: Thermal effects (tissue heating); concerns about mobile phone use and brain cancer (WHO IARC: Group 2B - possibly carcinogenic)

Radiation Protection (ALARA Principle)

1. Time - minimize time of exposure
2. Distance - maximize distance from source (inverse square law: dose ∝ 1/d²)
3. Shielding - use appropriate shielding (lead aprons, lead glass, concrete walls)

• Whole body: 20 mSv/year (averaged over 5 years, max 50 mSv/year)
• Lens of eye: 150 mSv/year
• Extremities: 500 mSv/year
• Pregnant radiation workers: 1 mSv for the remainder of pregnancy after declaration
• General public: 1 mSv/year (excluding medical exposures)

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Q8. Oxidation Pond (3M)

Definition

Mechanism of Action

1. Bacteria (heterotrophs) decompose organic matter in sewage → produce CO₂, NH₃, H₂S, PO₄³⁻
2. Algae use CO₂ + sunlight (photosynthesis) → produce O₂
3. This O₂ from algae is used by bacteria for aerobic decomposition
4. Algae use the nutrients (N, P) released by bacterial action
5. UV radiation from sunlight kills most pathogens

Types of Oxidation Ponds

1. Aerobic pond - shallow (0.5-1.5 m); well-oxygenated throughout; algae predominate; handles dilute sewage
2. Anaerobic pond - deep (2-5 m); no dissolved oxygen; handles concentrated sewage (slaughterhouse waste); anaerobic digestion
3. Facultative pond (most common) - three zones: surface aerobic layer (algae+O₂), middle facultative zone, bottom anaerobic layer (sludge)

Design Parameters

• Depth: 1-2 m (facultative pond)
• Surface loading: 100-400 kg BOD/hectare/day
• Retention time: 5-30 days
• Must be built as series of 2-3 ponds in series for optimal treatment

Advantages

• Inexpensive to construct and operate (no energy for aeration)
• Low maintenance; no skilled operators required
• Suitable for developing countries and rural areas
• Effective reduction of BOD (up to 80-90%), pathogens, and helminth eggs
• Treats both domestic and industrial wastewater

Disadvantages

• Requires large land area
• Efficiency depends on sunlight and temperature (less effective in cold/cloudy climates)
• Nuisance (odour, insects) if improperly operated or overloaded
• Not suitable for densely populated urban areas

Applications in India

• Widely used in small towns and municipal areas
• Used for treating sewage before land application (irrigation)

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Q9. Colour Coding for Biomedical Waste (3M)

Key Points to Remember

• ONLY 4 colours under 2016 Rules (previously 10 categories under 1998 Rules)
• Yellow = most infectious/anatomical → incineration
• Red = plastic recyclables → after decontamination
• White = sharps → puncture-proof container mandatory
• Non-BMW general waste (food waste, paper, etc.) should be collected in black bags (municipal solid waste stream)
• All BMW containers must be labelled with biohazard symbol and name/address of healthcare facility

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Q10. Insecticides (3M)

Definition

Classification of Insecticides

A. By Chemical Class

B. By Use in Public Health

• IRS (Indoor Residual Spraying): DDT (1-2 g/m²), Malathion, Synthetic pyrethroids (Deltamethrin, Bifenthrin) - sprayed on walls and ceilings
• Space spraying (fogging): Malathion (ultra-low volume fogging for dengue), Permethrin - for adult mosquito knockdown
• Larviciding: Temephos (Abate) in water containers, Paris green, Pyrethrum extract

• Repellents: DEET (N,N-Diethyl-meta-toluamide) - most effective; applied to skin/clothing; protects against Aedes, Anopheles; duration 2-12 hours
• Permethrin: Applied to clothing/nets; not applied to skin; effective for mosquitoes and ticks

• Deltamethrin or Permethrin incorporated into net fibres; effective for 3-5 years

Hazards of Insecticides

• OP and carbamate toxicity: Cholinergic syndrome (SLUDGE: Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis); miosis, bradycardia; Treatment: Atropine (antidote); Pralidoxime (for OPs within 24-48 hrs)
• Pyrethroid toxicity: Paraesthesia, dizziness (low systemic toxicity)
• DDT/OC toxicity: CNS stimulation, seizures; environmental persistence (bioaccumulation through food chain)
• Resistance - major challenge; rotate insecticides with different modes of action

Insecticide Resistance Management

• WHO recommends rotation of insecticide classes
• Regular resistance monitoring by sentinel sites
• Combined use of non-insecticidal vector control methods (source reduction, biological control)

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• Water treatment steps: S-C-S-D (Storage → Coagulation → [Sand] Filtration → Disinfection)
• BMW colours: "Your Red White Blood" → Yellow-Red-White-Blue
• Occupational hazards: "Physical, Chemical, Biological, Mechanical, Psychosocial" = PCBMP
• Insecticide antidote (OP): Atropine (muscarinic blocker) + Pralidoxime (reactivates AChE)