Pediatrics Essay: Dengue, DPT (Diphtheria, Pertussis, Tetanus), and Pediatric Tuberculosis

PART I: DENGUE IN CHILDREN

Definition and Etiology

Epidemiology

Clinical Manifestations

Diagnosis

• RT-PCR (dengue RNA) and NS1 antigen EIA: positive from symptom onset through Day 7–10
• Anti-dengue IgM EIA: detectable from Day 3–5; 99% of patients are positive by Day 10; remains detectable up to 2–3 months
• Anti-dengue IgG: persists lifelong; a fourfold rise between acute (≤Day 5) and convalescent (>Day 15) specimens confirms recent infection
• Testing NS1 antigen + IgM on a single specimen within the first 10 days identifies ≥90% of cases
• Tourniquet test (capillary fragility test): inflate BP cuff midway between systolic and diastolic pressure for 5 minutes; ≥10 petechiae per inch² is positive

Management

• Febrile phase: Maintain hydration; avoid aspirin, NSAIDs (ibuprofen), and salicylates (increase bleeding risk). Paracetamol is the analgesic of choice.
• Critical phase: Intensive monitoring for shock, occult bleeding, and plasma leakage. Maintain fluid volume and hemodynamic status. Use oral or IV crystalloids for mild–moderate dehydration; IV colloids and/or blood products for refractory shock.
• Reabsorption phase: Avoid fluid overload; reduce IV fluids as extravascular fluid returns to circulation.
• Early recognition and intensive supportive care reduces mortality from severe dengue from 5–10% to <1%.

Prevention and Vaccination

• Vector control: Elimination of Aedes breeding sites (standing water).
• Personal protection: EPA-registered repellents, protective clothing, screened/air-conditioned accommodation; day-biting mosquitoes mean bed nets are particularly important for children sleeping during the day.
• Dengvaxia (CYD-TDV): Recombinant live attenuated tetravalent dengue vaccine. FDA-approved in the US for ages 9–16 years residing in endemic areas with prior laboratory-confirmed dengue infection. NOT recommended for dengue-naive individuals — seronegative vaccine recipients show an increased hazard ratio for severe dengue upon subsequent infection (antibody-dependent enhancement). Given as 3 doses at 0, 6, and 12 months.

PART II: DPT — DIPHTHERIA, PERTUSSIS, AND TETANUS

A. DIPHTHERIA

Definition and Etiology

Epidemiology

Clinical Manifestations

• Membranous nasopharyngitis: Sore throat, malaise, dysphagia, low-grade fever, with the formation of a characteristic thick, gray adherent pseudomembrane over the tonsils and soft palate. The membrane bleeds on attempted removal — a hallmark sign.
• Obstructive laryngotracheitis: Classic "barking" cough, stridor, hoarseness, and respiratory difficulty.
• Bull neck: Extensive cervical lymphadenitis with marked neck edema — a sign of severe disease.
• Nasal diphtheria: Serosanguineous or bloody nasal discharge.

• Upper airway obstruction due to membrane extension
• Myocarditis with heart block (most common cause of death)
• Cranial and peripheral neuropathies: Palatal palsy (nasal voice, regurgitation) is an early sign of pharyngeal diphtheria; later neuropathies include oculomotor paralysis and diaphragmatic paralysis leading to respiratory failure
• Case fatality rate: 5–10%; up to 50% in untreated patients

Diagnosis

• Confirmed by isolation of C. diphtheriae on culture of a nasopharyngeal swab (Loeffler's medium; tellurite agar)
• Toxigenicity testing (Elek test or PCR for the tox gene) confirms toxigenic status

Treatment

1. Diphtheria antitoxin (equine): Administered as early as possible without waiting for culture results — neutralizes unbound toxin. Requires skin testing for hypersensitivity first.
2. Antibiotics: Erythromycin or penicillin G for 14 days — to eradicate organisms and prevent transmission. Bacteriologic proof of eradication required before discharge.
3. Respiratory support as needed; strict isolation.

Prevention and Immunization

• DTaP (diphtheria, tetanus toxoid, acellular pertussis): 5 doses for children from 2 months through 6 years of age — at 2, 4, 6, 15–18 months, and 4–6 years
• Tdap booster at age 11–12 years; Td booster every 10 years thereafter
• Children <7 years in whom pertussis vaccine is contraindicated receive DT
• Close contacts: Antimicrobial prophylaxis (oral erythromycin 40–50 mg/kg/day for 7–10 days, or penicillin G benzathine IM) + surveillance for 7 days + culture; booster vaccination if >5 years since last dose.

B. PERTUSSIS (WHOOPING COUGH)

Definition and Etiology

Epidemiology

Clinical Manifestations — Three Classic Stages

• An inspiratory "whoop" (gasp after prolonged coughing bout) — present in children >2–3 years but occurs in only ~6% of all cases
• Post-tussive emesis (vomiting after coughing)
• Cyanosis and apnea in young infants (<6 months)
• Fever is typically absent or minimal
• Physical examination between paroxysms is remarkably normal

• Infants <6 months: Atypical — short or absent catarrhal stage; prominent gasping, gagging, bradycardia, apnea may be the presenting features; no whoop; high morbidity and mortality; sudden unexpected death can occur.
• Immunized children and adolescents: Milder, prolonged cough; typical stages may not be present; persistent dry cough lasting ≥3 weeks is the hallmark.

• Pneumonia (most common complication, from secondary bacterial infection)
• Pulmonary hypertension (severe complication in young infants)
• Apnea (especially in young infants)
• Seizures (~0.9% of infants)
• Encephalopathy (<0.5%)
• Conjunctival hemorrhage, hernias, rib fractures (from forceful coughing)
• Case fatality rate: ~1.6% in infants <2 months; <1.2% in infants 2–11 months

Diagnosis

• Complete blood count: Marked lymphocytosis (WBC often 20,000–100,000/µL) — a key diagnostic clue
• Nasopharyngeal culture on Bordet-Gengou or Regan-Lowe agar: gold standard; best yield during the catarrhal or early paroxysmal stage; sensitivity declines after week 4 or in vaccinated patients
• PCR (Nasopharyngeal swab/aspirate): High sensitivity; faster turnaround; method of choice especially in clinical and early paroxysmal stages
• Serology (IgG anti-pertussis toxin): useful in later disease and for epidemiologic studies
• Chest X-ray: may show "shaggy right heart border" (perihilar infiltrates) or be normal

Treatment

• Antibiotics (macrolides — first-line):
  • Azithromycin: Drug of choice for infants <1 month (preferred over erythromycin to avoid infantile hypertrophic pyloric stenosis); also used in older children and adults
  • Erythromycin: 40–50 mg/kg/day for 14 days (avoid in neonates)
  • Clarithromycin: Alternative for children ≥1 month
  • TMP-SMX: Alternative when macrolides are contraindicated
  • Note: Antibiotics eradicate the organism and reduce transmission. They do NOT alter disease course once the paroxysmal stage has begun, but are still given to limit spread.
• Infants <3–6 months with presumed pertussis should be hospitalized for monitoring (apnea risk), supportive care, and IV fluids if necessary.
• Contacts: Postexposure prophylaxis with azithromycin or erythromycin for all close contacts regardless of vaccination status.

Prevention and Immunization

• DTaP (acellular pertussis) vaccine: Primary series at 2, 4, 6 months; booster at 15–18 months and 4–6 years. Immunization is only ~80% effective after three doses.
• Tdap booster at 11–12 years
• Maternal Tdap immunization during each pregnancy (ideally 27–36 weeks gestation): reduces morbidity and mortality in young infants through passive transfer of maternal antibodies — the "cocooning" strategy
• Vaccination of all healthcare workers with Tdap is recommended
• 3-week isolation of confirmed cases from susceptible individuals (infants, unvaccinated)

C. TETANUS

Overview in Pediatrics

• Caused by contaminated umbilical cord stump (unsterile cutting, application of cow dung or ash)
• Occurs in neonates born to unimmunized or inadequately immunized mothers
• Onset: Day 3–14 of life
• Presents as inability to suck (trismus of jaw muscles), risus sardonicus (facial spasm), opisthotonus, and generalized spasms triggered by light, sound, or touch
• High mortality (up to 80–90% without treatment) in resource-limited settings
• Prevention: Maternal immunization with tetanus toxoid (2 doses in pregnancy), clean delivery and cord care

• Incubation: 3–21 days after wound; shorter incubation = more severe disease
• Trismus (lockjaw) — most common initial symptom
• Risus sardonicus (characteristic facial grimace)
• Opisthotonus (arching of the back)
• Autonomic instability: hypertension, tachycardia, sweating
• Reflex spasms triggered by stimuli → laryngospasm → respiratory failure
• Complications: aspiration pneumonia, rhabdomyolysis, fractures, autonomic crisis

1. Human Tetanus Immune Globulin (HTIG) 3,000–6,000 units IM — to neutralize unbound toxin
2. Wound debridement
3. Antibiotics: Metronidazole (drug of choice) or penicillin G — to eradicate C. tetani
4. Diazepam / Midazolam for muscle spasm control; magnesium sulfate for autonomic instability in severe cases
5. Supportive: ICU care, mechanical ventilation if needed, minimize stimulation
6. Tetanus toxoid vaccination (since disease does not confer immunity)

Td = adult-type tetanus + reduced-dose diphtheria; Tdap = Td + acellular pertussis; DTaP = full-dose diphtheria + tetanus + acellular pertussis for children <7 years

PART III: PEDIATRIC TUBERCULOSIS

Definition and Etiology

Epidemiology

• TB is encountered commonly in immigrant and refugee children from high-prevalence countries
• Children <5 years are at greatest risk of progression from infection to active disease and of developing disseminated (miliary) TB and TB meningitis
• TB in children often signals an infectious adult source in the household — family testing is mandatory when a child is diagnosed
• BCG vaccine (Bacille Calmette-Guérin): Widely used in countries with high TB incidence; ~80% efficacy against lethal forms (meningitis, miliary) in children but lower efficacy against pulmonary TB. BCG is NOT a contraindication to tuberculin skin testing.

Pathogenesis

Clinical Features

1. Primary TB is often asymptomatic — identified only through contact tracing or screening programs
2. When symptomatic: fever, cough, wheezing, poor feeding, fatigue, failure to thrive
3. Classic symptoms of fever, night sweats, and weight loss are more typical in older children
4. Children <5 years may present directly with miliary TB, TB meningitis, or a pneumonia not responding to standard antibiotics
5. Hilar lymphadenopathy (± patchy infiltrate) is the most common chest radiographic finding — not upper lobe cavitary disease (which is adult-type secondary TB)
6. Children are at greater risk of rapidly progressive and disseminated disease compared to adults

• Cervical lymphadenitis (scrofula): Most common extrapulmonary site — rubbery, nontender nodes matting together; may form cold abscess (no erythema, no warmth) that discharges to form a sinus tract
• TB Meningitis: Insidious onset — 2–3 weeks of fever, headache, meningismus, cranial nerve palsies (CN VI, III, IV), altered sensorium; CSF shows lymphocytic pleocytosis, elevated protein, low glucose. High mortality and neurologic sequelae.
• Miliary TB: Hematogenous dissemination — diffuse 1–3 mm nodules on CXR ("millet seeds"); multi-organ involvement; high mortality; choroidal tubercles on fundoscopy are pathognomonic
• Bone and Joint TB: More common in children than adults; spine (Pott's disease), large joints (hip, knee)
• Other sites: pericardium, abdomen, kidneys, skin, eyes

Diagnosis

1. Difficulty obtaining adequate sputum specimens in young children
2. Paucibacillary nature of disease (low bacterial burden)
3. Culture confirmation achieved in only 30–40% of pediatric cases

• Tuberculin Skin Test (TST/Mantoux test): Preferred for children <2 years; 0.1 mL of PPD (5 TU) ID in the volar forearm; read at 48–72 hours; induration (not erythema) is measured:
  • ≥5 mm: HIV+, immunocompromised, close contact with active TB, abnormal CXR
  • ≥10 mm: Children <4 years, high-risk populations, immigrants from endemic areas
  • ≥15 mm: Low-risk individuals (not routinely tested)
  • False-positive: BCG vaccination, nontuberculous mycobacteria → use IGRA in BCG-vaccinated children ≥2 years
  • False-negative: Malnutrition, disseminated/miliary TB, immunosuppression, early infection
• Interferon-Gamma Release Assay (IGRA) (QuantiFERON-TB Gold, T-SPOT.TB): Preferred for BCG-vaccinated children ≥2 years (less affected by prior BCG). Not recommended for children <5 years — immune response differs, making tests less reliable.
• Sputum/Gastric aspirate: Acid-fast bacilli (AFB) smear + mycobacterial culture. Three early-morning consecutive gastric lavage specimens have been the traditional approach in young children (who cannot expectorate). Sputum induction (bronchodilators + nebulized hypertonic saline) can improve yield non-invasively.
• NAAT (Nucleic Acid Amplification Testing): Not recommended as the primary test in children <5 years; useful as adjunct.
• Chest Radiograph: Hallmarks in children: hilar lymphadenopathy, patchy infiltrate. Upper lobe cavitary disease suggests secondary (reactivation) TB. CXR may be normal even with active disease in children.
• Lumbar puncture if meningitis is suspected; CT/MRI brain for hydrocephalus, tuberculomas
• Often, treatment is initiated on clinical and epidemiological grounds (symptoms + history of exposure + positive TST/IGRA + abnormal CXR) without bacteriologic confirmation.

Treatment

1. Multidrug therapy for all children with active disease (prevents resistance)
2. Directly Observed Therapy (DOT) is strongly recommended
3. Drug susceptibility testing must be performed wherever possible

• Given at birth in endemic countries (WHO recommendation)
• Protects ~80% against meningitis and miliary TB in children
• Does not prevent primary infection or adult-type pulmonary TB reliably
• Not routinely given in the United States (use of TST would be unreliable)

Summary Table

• Red Book 2021: Report of the Committee on Infectious Diseases, American Academy of Pediatrics
• Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9th Edition
• Rosen's Emergency Medicine: Concepts and Clinical PracticeThe essay above is a comprehensive, exam-ready pediatrics essay covering all three requested topics. Here is a quick map of what was covered:

• Etiology (4 Flavivirus serotypes), epidemiology (infants at highest risk for severe disease), pathophysiology of antibody-dependent enhancement
• WHO 2009 severity classification (dengue without/with warning signs / severe dengue)
• Three clinical phases (febrile → critical → convalescent) with timing
• Diagnosis: NS1 antigen + IgM EIA + RT-PCR; tourniquet test
• Management: supportive, no NSAIDs/aspirin, fluid therapy in critical phase
• Dengvaxia vaccine — only for seropositive children ≥9 years

• Diphtheria: pseudomembrane formation, bull neck, ADP-ribosylase toxin mechanism, myocarditis + neuropathy complications, antitoxin + erythromycin treatment, DTaP schedule
• Pertussis: three stages (catarrhal → paroxysmal → convalescent), infants <6 months have atypical apneic presentation, marked lymphocytosis, azithromycin treatment, maternal Tdap strategy
• Tetanus: neonatal tetanus (contaminated cord) vs. generalized tetanus in children, HTIG + metronidazole + diazepam management, DTaP schedule table

• Primary vs. secondary TB, Ghon complex formation
• Unique pediatric features: often asymptomatic, hilar lymphadenopathy (not cavitary disease), high dissemination risk in <5 years
• Extrapulmonary sites: scrofula, TB meningitis, miliary TB, Pott's disease
• Diagnostic challenges: TST (preferred <2 yrs), IGRA (preferred in BCG-vaccinated ≥2 yrs), gastric aspirate AFB, NOT IGRA/NAAT in <5 yrs
• Regimens: 2HRZE/4HR for pulmonary; 2HRZE/10HR for meningitis/miliary; dexamethasone adjunct for meningitis