26.4 Pediatric Infectious Diseases: Bacterial (Diphtheria to Congenital Syphilis), Childhood TB, Viral Exanthems and Infections, Dengue in Children, Pediatric HIV, Protozoal, Helminthic and Fungal Infections
Key Takeaways
Childhood TB is often smear-negative, so diagnosis combines exposure history, symptoms, TST or IGRA, chest X-ray and Xpert testing of sputum, gastric aspirate or stool.
Diphtheria needs equine antitoxin given without waiting for culture, plus penicillin or erythromycin; close contacts get prophylaxis and vaccination.
Herpangina (coxsackie A) causes vesicles on the posterior palate and fauces; herpetic gingivostomatitis (HSV-1) causes anterior oral ulcers and swollen bleeding gums.
In children with dengue, fluids are calculated by ideal body weight and adjusted to hematocrit and urine output; NSAIDs, aspirin and IM injections are avoided.
Oral thrush in an infant is treated with nystatin suspension; recurrent or severe candidiasis beyond infancy should prompt evaluation for immunodeficiency including HIV.
Why this area matters
The TOS asks you to take a clinical scenario of a common infection, "based on the latest data of the DOH", and then:
- identify the organism and pathogenesis;
- arrive at a diagnosis;
- prioritize and interpret tests;
- give the differential diagnosis.
The organisms are covered by organ system in Microbiology. This section concentrates on how they present and are managed in children. Pneumonia, diarrhea, dengue, measles, TB and neonatal infections remain leading causes of childhood illness and death in the Philippines.
Bacterial infections in children
| Infection | Pediatric features | Key management |
|---|---|---|
| Diphtheria | Unvaccinated child; sore throat, low fever, gray adherent pseudomembrane, bull neck; myocarditis and neuritis later | Diphtheria antitoxin at once on clinical suspicion, plus penicillin or erythromycin; isolate; prophylaxis and vaccination for contacts |
| Pertussis | Young infants: apnea, cyanosis and paroxysmal cough without a whoop; marked lymphocytosis | Azithromycin for patient and contacts; Tdap in pregnancy |
| Tetanus | Neonatal tetanus (days 3 to 14: stops sucking, trismus, spasms) after unclean cord care | Human tetanus immune globulin, metronidazole, diazepam, airway; wound and cord care |
| Hib, pneumococcus, meningococcus | Meningitis, pneumonia, bacteremia, epiglottitis (Hib), purpura fulminans (meningococcus) | Ceftriaxone; vaccines (pentavalent, PCV); prophylaxis for meningococcal contacts |
| Streptococcal (group A) | Pharyngitis (over age 3), impetigo, scarlet fever, cellulitis; acute rheumatic fever and post-streptococcal glomerulonephritis | Penicillin or amoxicillin for 10 days |
| Salmonella | Typhoid (school age); non-typhoidal bacteremia in infants and sickle cell disease | Azithromycin or ceftriaxone |
| Shigella | Dysentery, high fever, febrile seizures, HUS | Ciprofloxacin or azithromycin |
| Cholera, E. coli | Watery diarrhea; HUS from EHEC | Rehydration; zinc; antibiotics only for cholera or dysentery |
| Leptospirosis | After wading in floods; fever, myalgia, conjunctival suffusion, jaundice, renal failure | Doxycycline (8 years and older) or amoxicillin; penicillin or ceftriaxone if severe |
| Gonorrhea | Ophthalmia neonatorum; in older children suspect sexual abuse | Ceftriaxone |
| Congenital syphilis | Snuffles, rash on palms and soles, hepatosplenomegaly, periostitis, pseudoparalysis | Aqueous penicillin G for 10 days |
Childhood tuberculosis
- Natural history: children usually acquire TB from an infectious adult in the household. Young children (under 5) progress quickly to miliary TB and TB meningitis.
- Presentation:
- persistent cough of 2 weeks or more;
- fever;
- weight loss or failure to thrive;
- fatigue and reduced playfulness;
- cervical lymphadenitis;
- spinal deformity.
- Diagnosis:
- children rarely produce smear-positive sputum, so diagnosis combines close contact with a TB patient, symptoms, TST or IGRA, chest X-ray (hilar lymphadenopathy, miliary pattern) and Xpert MTB/RIF on sputum, induced sputum, gastric aspirate or stool;
- a negative test does not exclude TB, and the NTP allows clinical diagnosis.
- Treatment:
- drug-susceptible pulmonary TB: 2HRZE/4HR with weight-based pediatric fixed-dose combinations (non-severe disease may be treated for 4 months);
- TB meningitis and osteoarticular TB: longer courses;
- pyridoxine is given with isoniazid when there is malnutrition or HIV.
- Prevention: BCG at birth, and TB preventive treatment for household contacts after active TB is excluded.
Differential Diagnosis of Classic Pediatric Exanthems
Infectious exanthems represent a major category of pediatric board exam vignette questions.
| Disease & Etiology | Incubation & Prodrome | Pathognomonic Enanthem & Exanthem Morphology | Rash Distribution & Progression | Associated Findings & Complications |
|---|---|---|---|---|
| Measles (Rubeola) (Paramyxovirus / RNA Morbillivirus) | Incubation: 10-14 days. Prodrome (3-4 days): High fever (), malaise, and the 3 Cs: Cough, Coryza, and Conjunctivitis with marked photophobia. | Enanthem: Koplik spots — pathognomonic tiny, bluish-white grains on an erythematous base on the buccal mucosa opposite lower molars (appear 1-2 days before rash). Exanthem: Red, maculopapular rash that becomes confluent. | Begins at the hairline, forehead, and behind the ears, spreads cephalocaudally over 3 days to face, trunk, and extremities. Fades in same order with fine branny desquamation and brownish staining. | Complications: Otitis media (most common), severe bronchopneumonia (leading cause of death), encephalitis, and Subacute Sclerosing Panencephalitis (SSPE, late fatal neurodegeneration). Treatment: Supportive + High-Dose Vitamin A (100,000-200,000 IU). |
| Rubella (German Measles) (Togavirus / RNA Rubivirus) | Incubation: 14-21 days. Prodrome: Mild low-grade fever, headache, ocular pain; minimal symptoms in young children. | Enanthem: Forchheimer spots — pinpoint petechial hemorrhages on the soft palate. Exanthem: Pink, fine maculopapular rash; does not coalesce. | Begins on the face and spreads rapidly downward to trunk and limbs within 24 hours; completely disappears by day 3 ('3-day measles'). | Prominent, tender postauricular, suboccipital, and posterior cervical lymphadenopathy. Teratogenic Risk: Congenital Rubella Syndrome (CRS): patent ductus arteriosus (PDA), sensorineural deafness, cataracts, microcephaly, and 'blueberry muffin' skin lesions. |
| Roseola Infantum (Exanthema Subitum) (HHV-6) | Incubation: 9-10 days. Affects infants aged 6 to 18 months. Abrupt onset of very high fever () lasting 3 to 5 days; child remains surprisingly active and alert. | Enanthem: Nagayama spots (erythematous papules on soft palate/uvula). Exanthem: Discrete, rose-pink, non-pruritic macules and papules (2-5 mm) with pale halos. | Fever terminates precipitously by crisis, followed immediately by the sudden eruption of the rash on the neck and trunk, spreading minimally to face and extremities. Fades in 24-48 hours. | High risk for febrile seizures during the rapid, steep temperature rise. Self-limiting; supportive antipyretic care. |
| Erythema Infectiosum (Fifth Disease) (Parvovirus B19) | Incubation: 4-14 days. Minimal prodrome (mild headache, coryza, low-grade fever). | Phase 1: Bright fiery red erythema on cheeks ('slapped-cheek' appearance) with circumoral pallor. Phase 2: 1-4 days later, erythematous maculopapular eruption on extremities and trunk evolves into a classic reticular, lacy network pattern. Phase 3: Rash waxes and wanes for weeks, exacerbated by sunlight, heat, or exercise. | Concentrated on face (cheeks), extensor limbs, and trunk. Sparing of palms and soles. | Complications: Transient Aplastic Crisis in patients with underlying chronic hemolysis (sickle cell disease, hereditary spherocytosis, thalassemia); hydrops fetalis and intrauterine fetal demise following maternal infection during pregnancy. |
| Varicella (Chickenpox) (Varicella-Zoster Virus / VZV) | Incubation: 10-21 days. Prodrome (24-48h): Fever, malaise, anorexia, headache. | Exanthem: Intensely pruritic red macules that rapidly evolve into papules, then clear, thin-walled vesicles on an erythematous base ('dewdrops on a rose petal'), which umbilicate, become pustular, and crust over. | Centripetal distribution: begins on scalp and trunk, spreading outward to extremities. Hallmark: lesions exist in all stages of development simultaneously (macules, papules, vesicles, crusts). Highly contagious until all lesions are crusted. | Complications: Secondary bacterial superinfection (S. aureus, S. pyogenes necrotizing fasciitis); cerebellar ataxia; Reye syndrome if exposed to aspirin. |
| Hand, Foot, and Mouth Disease (HFMD) (Coxsackievirus A16 and Enterovirus 71) | Incubation: 3-5 days. Low-grade fever, sore throat, malaise, anorexia. | Enanthem: Painful small vesicles on the buccal mucosa, tongue, and hard palate that rapidly ulcerate into shallow erosions with red borders. Exanthem: Tender, non-pruritic, oval, gray-white vesicles (3-7 mm) with an erythematous halo. | Located on the palms of hands, soles of feet, dorsum of fingers/toes, and buttocks. | EV71 serotype is associated with severe neurologic complications (aseptic meningitis, brainstem encephalitis, and fatal neurogenic pulmonary edema). |
Other viral infections in children
- Enteroviruses and coxsackie:
- herpangina (coxsackie A): fever and vesicles on the posterior palate, uvula and tonsillar pillars;
- hand, foot and mouth disease;
- aseptic meningitis;
- myocarditis and pericarditis (coxsackie B);
- pleurodynia.
- Herpes simplex: herpetic gingivostomatitis (HSV-1) in toddlers causes high fever, painful anterior oral ulcers and swollen, bleeding gums.
- Treat with oral acyclovir if seen early, and fluids, because dehydration is a risk.
- Eczema herpeticum in atopic dermatitis is an emergency.
- CMV and EBV: congenital CMV is the main cause of non-genetic hearing loss. EBV mononucleosis in children may be mild or cause airway obstruction from enlarged tonsils.
- Influenza: highest risk under 5 years and in chronic disease. Oseltamivir is given to high-risk or severely ill children. Aspirin is avoided (Reye syndrome).
- Mumps: parotitis, aseptic meningitis, orchitis after puberty and deafness.
- Dengue in children:
- warning signs and severe dengue are the same as in adults;
- infants and young children may present with shock without obvious bleeding, and some cases are mistaken for gastroenteritis;
- maintenance and deficit fluids are calculated from ideal body weight in obese children, given with isotonic crystalloids at rates titrated to vital signs, hematocrit and urine output (at least 0.5 mL/kg/hour);
- avoid NSAIDs, aspirin, IM injections and unnecessary platelet transfusions.
- Pediatric HIV:
- mostly from mother-to-child transmission;
- failure to thrive, recurrent infections, persistent thrush, parotid enlargement, lymphadenopathy and developmental delay;
- diagnosed by nucleic acid testing under 18 months;
- treated with ART for all children, cotrimoxazole prophylaxis and routine vaccines (BCG and other live vaccines are avoided in symptomatic or severely immunosuppressed children).
Protozoal, helminthic and fungal infections in children
- Amebiasis and giardiasis:
- amebic dysentery and liver abscess are treated with metronidazole and a luminal agent;
- giardiasis (malabsorption, poor growth) is treated with metronidazole or tinidazole.
- Enterobiasis: night-time perianal itch, diagnosed by the tape test; treat the whole household with albendazole, repeated after 2 weeks.
- Hookworm: iron deficiency anemia and poor growth.
- Schistosomiasis in endemic barangays causes hepatosplenomegaly and growth retardation in schoolchildren, and is treated with praziquantel.
- Malaria in children:
- more severe;
- presents with severe anemia, hypoglycemia, convulsions and cerebral malaria;
- severe malaria is treated with IV artesunate.
- Candida:
- oral thrush (white plaques that do not scrape off easily) is treated with nystatin suspension;
- diaper dermatitis involves the skin folds with satellite lesions, unlike irritant diaper dermatitis, and is treated with topical azoles;
- persistent or recurrent thrush beyond infancy suggests HIV or another immunodeficiency.
- Cryptococcus causes meningitis mainly in immunocompromised children, especially advanced HIV.
A 4-year-old unvaccinated child from a remote barangay has fever, sore throat, a swollen neck and a gray membrane over the tonsils and pharynx that bleeds when scraped. What is the most important immediate treatment?
Corticosteroids for infectious mononucleosis
Diphtheria antitoxin given without waiting for culture, plus penicillin or erythromycin
IV acyclovir for herpetic pharyngitis
Oral amoxicillin and a throat swab, with antitoxin only if the culture is positive
A 3-year-old with a household contact who has smear-positive pulmonary TB has had cough for 3 weeks, low-grade fever and weight loss. A TST shows 12 mm induration and the chest X-ray shows right hilar lymphadenopathy. He cannot produce sputum. What is the best next step?
Give isoniazid preventive treatment alone for 6 months
Obtain a gastric aspirate or stool for Xpert MTB/RIF and start TB treatment based on the clinical diagnosis
Wait for a sputum smear, because children are only treated if they are bacteriologically confirmed as smear-positive
Repeat the TST in 3 months before any treatment
A 2-year-old has high fever, refusal to eat and painful ulcers on the anterior tongue, lips and buccal mucosa, with red, swollen, bleeding gums. What is the most likely diagnosis?
Oral candidiasis
Hand, foot and mouth disease caused by enterovirus 71
Herpangina caused by coxsackie A virus
Herpetic gingivostomatitis caused by HSV-1
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