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Differentiation of Epidemiological Factors Among Major Communicable Diseases

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1. CHICKENPOX (Varicella)

• Prodrome: Mild fever, malaise, loss of appetite (1-2 days)
• Rash: Successive crops of macules -> papules -> vesicles -> pustules -> crusts; centripetal (trunk more than periphery)
• Lesions in all stages present simultaneously (pathognomonic)
• Intense pruritus
• Mild fever during rash phase
• Complications: Secondary bacterial infections, pneumonia, encephalitis, cerebellar ataxia; severe in immunocompromised, neonates, and adults

• Supportive: antipyretics (avoid aspirin - Reye's syndrome), calamine lotion for pruritus, antihistamines
• Antiviral: Acyclovir (800 mg 5x/day for 7 days in adults; 20 mg/kg 4x/day in children) - best within 24 hours of rash
• Varicella-Zoster Immunoglobulin (VZIG) for high-risk contacts

• Varicella vaccine (live attenuated): 2 doses (1st dose at 12-15 months; 2nd at 4-6 years)
• Isolation of cases until all lesions are crusted
• VZIG for susceptible high-risk contacts (immunocompromised, pregnant women, neonates) within 72-96 hours of exposure
• Good hygiene; avoid sharing personal items

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2. DIPHTHERIA

• Faucial (most common): Sore throat, low-grade fever, malaise, formation of a tough, grayish-white "pseudomembrane" on tonsils and pharynx that bleeds on removal
• Laryngeal: Hoarseness, stridor, "barking" cough, croup - risk of airway obstruction
• Nasal: Serosanguineous nasal discharge
• Toxaemic signs: Myocarditis (arrhythmias, heart failure), polyneuropathy (palatal palsy - nasal voice, blurred vision), "bull neck" (marked cervical lymphadenopathy + soft tissue swelling)
• Case fatality rate: 5-10% in untreated; up to 20% in children under 5 and adults over 40

• Diphtheria Antitoxin (DAT): Immediate administration (within 48 hrs gives greatest benefit); neutralizes free circulating toxin; dose depends on site and severity (20,000 - 100,000 units)
• Antibiotics: Penicillin (drug of choice) or Erythromycin for 14 days - to eliminate the organism
• Supportive: bed rest, airway management, cardiac monitoring
• Tracheostomy for laryngeal obstruction

• Active immunization: DPT (diphtheria-pertussis-tetanus) vaccine - cornerstone of prevention; 3 doses in infancy + booster doses
• Isolation of cases until 2 negative cultures from throat and nose
• Identification and treatment of carriers
• Contact tracing: all contacts should receive prophylactic penicillin/erythromycin and booster dose of diphtheria toxoid if not fully immunized
• Health education; improvement of socioeconomic conditions

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3. WHOOPING COUGH (Pertussis)

1. Catarrhal stage (1-2 weeks): Mild fever, runny nose, sneezing, mild cough - resembles common cold. Most infectious here.
2. Paroxysmal stage (2-4 weeks, up to 10 weeks): Violent paroxysms of cough followed by a characteristic "whoop" (loud crowing inspiratory sound), cyanosis, vomiting post-cough, petechiae on face/conjunctiva, exhaustion. Paroxysms triggered by feeding, crying, physical activity. May be absent in infants (apnoea instead).
3. Convalescent stage (weeks to months): Gradual decrease in frequency and severity of cough. Chinese call it "Hundred Day Cough."

• Complications: Pneumonia (most common cause of death), convulsions, encephalopathy, atelectasis, subconjunctival haemorrhage, rectal prolapse, hernia

• Antibiotics: Erythromycin (drug of choice) or Azithromycin/Clarithromycin; TMP-SMX as alternative - must be started in catarrhal stage to prevent progression; in paroxysmal stage, antibiotics reduce transmission but not symptoms
• Supportive: quiet environment, small frequent feeds, adequate hydration, oxygen for cyanosis
• Hospitalization for infants under 6 months
• Corticosteroids and albuterol may help in severe cases (limited evidence)

• DPT/DTwP/DTaP vaccine: Primary series with booster doses; acellular pertussis (aP) vaccine preferred in developed countries
• Tdap booster for adolescents and adults (including pregnant women - to protect newborns via maternal antibodies)
• Isolation of cases during catarrhal and early paroxysmal stage (at least 5 days after starting antibiotics)
• Chemoprophylaxis with erythromycin/azithromycin for household contacts, especially infants
• Prompt reporting and investigation of outbreaks

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4. TUBERCULOSIS (TB)

• Primary TB (often asymptomatic): Mild fever, fatigue, failure to thrive in children
• Post-primary/Pulmonary TB: Persistent productive cough (>2 weeks), blood-streaked sputum (haemoptysis), chest pain, evening rise of temperature, night sweats, progressive weight loss, anorexia, fatigue, dyspnoea
• Extrapulmonary TB: Lymphadenopathy (scrofula), meningitis (TB meningitis), pleural effusion, peritonitis, bone/joint TB (Pott's disease), renal TB, miliary TB (hematogenous spread - millet-seed lesions throughout lungs and organs)
• Complications: Respiratory failure, bronchopleural fistula, drug-resistant TB (MDR-TB, XDR-TB)

• First-line drugs (RIPE): Rifampicin (R), Isoniazid (I), Pyrazinamide (P), Ethambutol (E), Streptomycin (S)
• Intensive phase (2 months): HRZE (4 drugs)
• Continuation phase (4 months): HR (2 drugs)
• Total duration: 6 months (new cases); 9 months or longer for MDR-TB
• DOTS (Directly Observed Treatment, Short-course): Cornerstone of RNTCP; ensures treatment adherence
• MDR-TB: Second-line drugs (fluoroquinolones, injectable aminoglycosides, etc.) for 18-24 months
• HIV co-infection: ART plus anti-TB therapy

• BCG vaccination (Bacille Calmette-Guerin): Given at birth; 80% efficacy against miliary TB and TB meningitis in children; variable efficacy against pulmonary TB
• Early case detection and treatment (sputum smear microscopy, GeneXpert, culture)
• DOTS strategy - ensures completion of treatment
• Contact tracing and chemoprophylaxis with Isoniazid (6 months) for close contacts especially children and immunocompromised
• Infection control: ventilation, ultraviolet light, N95 respirators in healthcare settings
• Nutritional improvement; addressing HIV co-infection
• Pasteurization of milk; tuberculin testing of cattle

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5. MEASLES (Rubeola)

• Prodromal stage (3-4 days): High fever, coryza (runny nose), cough, conjunctivitis ("3 Cs"); Koplik's spots (pathognomonic - tiny white spots on buccal mucosa opposite lower molars) appear 1-2 days before rash
• Rash stage (3-4 days): Maculopapular rash starts on face/hairline, spreads downward to trunk and extremities; rash is blotchy and confluent; fever continues with rash
• Recovery stage: Rash fades in same order; brownish discoloration; branny desquamation
• Complications (major cause of morbidity/mortality): Pneumonia (most common cause of death), otitis media, croup, diarrhoea, encephalitis (1/1000 cases), subacute sclerosing panencephalitis (SSPE - rare, years later), malnutrition, vitamin A deficiency, xerophthalmia (particularly serious in malnourished children); "measles face" - swollen eyelids

• Supportive: rest, fluids, antipyretics, treatment of secondary infections
• Vitamin A supplementation (WHO recommendation): 200,000 IU for 2 days - reduces complications and mortality by 50% in deficient populations (50,000 IU under 6 months; 100,000 IU for 6-12 months)
• Antibiotics only for bacterial secondary infections (pneumonia, otitis media)
• No specific antiviral treatment

• Measles-containing vaccine (MCV): Live attenuated; 2 doses - 1st at 9-12 months, 2nd at 15-18 months (or entry to school); need 95% coverage for herd immunity
• MR/MMR vaccine covers measles + rubella (+ mumps)
• Supplementary Immunization Activities (SIAs) for outbreak control
• Isolation: 4 days from appearance of rash (respiratory isolation)
• Passive immunization: immunoglobulin within 6 days of exposure for susceptible contacts
• Vitamin A distribution in endemic areas; nutritional support

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6. MUMPS

• 30-40% infections are subclinical
• Parotitis: Pain and swelling of one or both parotid glands (most characteristic); "earache" on affected side precedes swelling; pain/stiffness on opening mouth; submandibular and sublingual glands may also be involved
• Fever, headache, malaise
• Complications:
  • Orchitis (20-30% of post-pubertal males; unilateral in majority; may lead to testicular atrophy but rarely causes infertility)
  • Oophoritis (5% of post-pubertal females)
  • Meningitis/Encephalitis (15% subclinical; clinical meningitis in 1-10%)
  • Pancreatitis (4%) - epigastric pain, nausea, vomiting
  • Sensorineural hearing loss (rare but permanent)
  • Mastitis, thyroiditis, myocarditis (rare)

• No specific antiviral treatment
• Supportive: analgesics, antipyretics, soft diet, adequate hydration, scrotal support for orchitis; corticosteroids for orchitis (limited evidence)
• Isolation during communicable period

• MMR vaccine (Measles-Mumps-Rubella): Live attenuated; 2 doses
• Isolation of cases until swelling has subsided (approximately 9 days after onset of parotitis)
• Quarantine of susceptible contacts in closed institutions
• Health education on respiratory hygiene

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7. RUBELLA (German Measles)

• Postnatal rubella is usually mild and self-limiting
• Low-grade fever (1-2 days prodrome in adults; rash often first sign in children)
• Lymphadenopathy: Post-auricular, occipital, posterior cervical - appears 5-10 days before rash; pathognomonic
• Rash: Minute, discrete, pinkish macular rash, starts on face, spreads to trunk and extremities; NOT confluent (unlike measles); disappears by 3rd day; may be pruritic; absent in 25% of cases
• Mild arthralgia (especially young women)
• Complications: Encephalitis (rare), thrombocytopenic purpura (rare)
• Congenital Rubella Syndrome (CRS - most serious): If infection in 1st trimester - deafness (most common), cataracts, cardiac defects (patent ductus arteriosus, pulmonary artery stenosis), microcephaly, mental retardation; infection risk to fetus is highest (85%) in first 8 weeks, decreasing as pregnancy progresses; >100,000 CRS babies born worldwide annually

• No specific antiviral treatment for postnatal rubella
• Supportive: analgesics for arthralgia, antipyretics
• Management of CRS complications (surgical correction of cardiac/eye defects, hearing aids)
• Termination of pregnancy may be considered if rubella acquired in 1st trimester

• MR/MMR vaccine: 2 doses; special emphasis on vaccinating women of childbearing age
• Rubella vaccination of all girls and women before pregnancy (confirm immunity by serology)
• Antenatal screening for rubella antibodies (immunity status)
• Isolation of postnatally infected cases for 1 week after rash onset
• Strict isolation of CRS infants (can shed virus for months)
• Health education on importance of pre-conception immunization

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8. ACUTE RESPIRATORY INFECTIONS (ARI)

• Upper ARI (UARI): Common cold, sinusitis, pharyngitis, tonsillitis, otitis media
• Lower ARI (LARI): Bronchitis, bronchiolitis, pneumonia (most dangerous)
• ARI accounts for approximately 12% of under-five mortality worldwide and 4 million deaths per year globally

• Sudden onset
• Upper ARI: Coryza, sore throat, nasal congestion/discharge, sneezing, hoarseness
• Lower ARI / Pneumonia (WHO danger signs): Fast breathing (tachypnoea - >50/min in 2-12 months; >40/min in 1-5 years), lower chest wall in-drawing (severe), stridor when calm (very severe), inability to feed (very severe), cyanosis
• Fever (>38°C), cough, malaise
• Severe ARI: dyspnoea, oxygen saturation <94%, altered consciousness

• No pneumonia (UARI only): Home treatment; supportive care (fluids, paracetamol, honey for cough in children >1 year); NO antibiotics
• Pneumonia: Outpatient oral amoxicillin (first-line); co-trimoxazole as alternative
• Severe pneumonia: Hospitalization; IV/IM benzylpenicillin or ampicillin + gentamicin; oxygen; IV fluids
• Very severe pneumonia: Same as severe + chloramphenicol if no improvement
• Antiviral therapy (oseltamivir) for influenza in high-risk patients
• Zinc supplementation in children (reduces incidence and duration)

• Vaccination: Influenza vaccine (annual), pneumococcal vaccine (PCV), Hib vaccine, RSV vaccine (newer), COVID-19 vaccines; Hib and pneumococcal vaccines part of national immunization programs
• Infant and young child feeding: Exclusive breastfeeding for 6 months - reduces ARI incidence and severity significantly
• Nutritional improvement (Vitamin A, zinc supplementation)
• Reduction of indoor air pollution (biomass fuel smoke is a major risk factor)
• Hand hygiene (handwashing with soap), respiratory etiquette (covering cough/sneeze)
• Prompt identification and treatment (IMCI - Integrated Management of Childhood Illness strategy)
• Infection control in healthcare settings: masks, N95 respirators, ventilation, isolation precautions

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COMPARATIVE SUMMARY TABLE

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1. Route of transmission: All spread by droplets/airborne, EXCEPT chickenpox which also spreads by direct contact with lesions. TB spreads via droplet nuclei (true airborne - long distance). Rubella uniquely has vertical/transplacental transmission causing CRS.
2. Most infectious period: Diphtheria and whooping cough are most infectious in the early/catarrhal stage (before diagnosis). Measles is most infectious before rash appears.
3. Pathognomonic features: Koplik's spots (measles), pseudomembrane (diphtheria), "whoop" (pertussis), parotitis (mumps), centripetal vesicular rash in mixed stages (chickenpox).
4. Vaccine-preventable diseases: All 8 are preventable by vaccines. DPT covers diphtheria + pertussis (+ tetanus). MMR covers measles + mumps + rubella. BCG covers TB (partially).
5. Specific therapy: Only diphtheria requires antitoxin. TB requires prolonged 6-month multi-drug DOTS therapy. Chickenpox responds to acyclovir. Measles management is unique in requiring Vitamin A supplementation.