# Seminar 04: Pediatric Infectious Diseases ## Year 3: Pediatrics Clerkship --- ## Learning Objectives By the end of this seminar, students will be able to: 1. Evaluate fever in infants and children 2. Recognize and manage common viral infections 3. Diagnose and treat bacterial infections 4. Apply principles of antibiotic selection 5. Describe serious bacterial infections in children 6. Manage vaccine-preventable diseases --- ## Seminar Outline ### I. Fever in Children Fever in pediatric patients is defined as a temperature of 38 degrees Celsius (100.4 degrees Fahrenheit) or higher, representing the most common reason for emergency department visits in children. Accurate temperature measurement is essential for appropriate clinical decision-making, with rectal temperature providing the most reliable assessment in infants and young children. Axillary temperatures underestimate core temperature and should prompt addition of 0.5 to 1 degree Celsius when interpreting results, while tympanic measurements demonstrate variable accuracy in infants due to the small external auditory canal size. Oral temperatures are appropriate for children old enough to cooperate with proper thermometer placement under the tongue with closed mouth. The approach to febrile children varies dramatically by age, with younger infants at highest risk for serious bacterial infection due to immature immune function and the difficulty of clinical assessment. Neonates aged zero to twenty-eight days with fever require full sepsis evaluation including complete blood count with differential, blood culture, urinalysis with catheterized specimen and culture, lumbar puncture with cerebrospinal fluid analysis and culture, and chest radiograph if respiratory symptoms are present. These infants require admission and empiric antibiotic therapy pending culture results regardless of clinical appearance, as they may appear well despite life-threatening bacterial infection. Infants aged twenty-nine to sixty days represent an intermediate risk group for whom various clinical decision rules have been developed to identify those at low risk for serious bacterial infection. The Rochester criteria, Philadelphia protocol, and more recent Step-by-Step approach use combinations of clinical appearance, laboratory values, and historical factors to stratify risk. Low-risk infants who meet stringent criteria and have reliable follow-up may be managed as outpatients with close return precautions, though many clinicians prefer inpatient observation. High-risk infants in this age group require the same full evaluation and empiric antibiotic treatment as neonates. Beyond sixty days of age, clinical appearance becomes increasingly reliable for distinguishing ill from well children, and the approach to fever becomes more selective. Well-appearing infants aged sixty-one to ninety days may undergo targeted evaluation based on clinical findings, with urinalysis particularly important given the prevalence of urinary tract infection in this age group. Children older than ninety days can often be evaluated primarily on clinical grounds, with laboratory testing and imaging directed by history and physical examination findings. The presence of an identifiable source of infection, toxic appearance, or concerning vital signs guides the level of evaluation and treatment intensity. Panel A: Flowchart demonstrating the age-based approach to febrile infants from birth through ninety days with decision points and workup requirements. Panel B: Comparison table of Rochester, Philadelphia, and Step-by-Step criteria for low-risk identification in febrile infants aged 29-60 days. Panel C: Diagram illustrating proper temperature measurement techniques including rectal, axillary, tympanic, and oral methods with age-appropriateness. Panel D: Clinical photograph of a well-appearing versus toxic-appearing infant with distinguishing features highlighted. --- ### II. Common Viral Infections Upper respiratory tract infections represent the most frequent infectious illness in children, caused predominantly by rhinoviruses but also adenoviruses, coronaviruses, influenza, parainfluenza, and respiratory syncytial virus. Symptoms include nasal congestion, rhinorrhea progressing from clear to mucoid to purulent (which does not indicate bacterial superinfection), cough, low-grade fever, and mild pharyngitis. The typical duration of seven to ten days should be communicated to parents to set appropriate expectations and prevent unnecessary return visits or antibiotic requests. Management is supportive with adequate hydration, antipyretics for discomfort, and nasal saline for congestion, while decongestants and cough suppressants are not recommended for children under six years due to lack of efficacy and potential for harm. Viral gastroenteritis causes significant morbidity in young children, with rotavirus historically the most severe cause prior to widespread vaccination, and norovirus now the leading etiology. Presentation includes vomiting, often preceding diarrhea, low-grade fever, and abdominal cramping. The primary therapeutic concern is preventing and treating dehydration through oral rehydration therapy using balanced glucose-electrolyte solutions that exploit sodium-glucose cotransport. Antidiarrheal medications are contraindicated in children due to concerns for ileus and prolonged infection. The BRAT diet (bananas, rice, applesauce, toast) is no longer recommended, with continuation of regular diet including age-appropriate feeding encouraged once rehydration is achieved. Roseola, caused by human herpesvirus 6, presents with a distinctive clinical pattern in infants aged six months to two years. The illness begins with high fever often exceeding 40 degrees Celsius lasting three to five days, during which the child may appear surprisingly well between fever peaks. Febrile seizures occur in approximately 10-15% of cases, representing a common trigger for first febrile seizures. The diagnostic rash appears as the fever defervesces, consisting of pink maculopapular lesions starting on the trunk and spreading to the extremities and face. Treatment is supportive, and recognition of the classic pattern prevents unnecessary evaluation and antibiotic treatment. Fifth disease, caused by parvovirus B19, produces the characteristic "slapped cheek" facial erythema followed by a lacy, reticular rash on the trunk and extremities. A mild prodrome of fever and malaise may precede the rash by seven to ten days, during which the child is most contagious. By the time the rash appears, the child is no longer infectious and may return to daycare or school. Of particular clinical importance is the aplastic crisis that occurs when children with chronic hemolytic anemia such as sickle cell disease are infected, as parvovirus B19 targets erythroid precursors and halts red blood cell production. Pregnant contacts should be counseled regarding the risk of fetal hydrops from transplacental infection. Panel A: Timeline illustration showing the typical course of viral upper respiratory infection with symptom progression over 7-10 days. Panel B: Comparison of oral rehydration solutions with appropriate glucose-electrolyte composition versus inappropriate alternatives such as juice and sports drinks. Panel C: Classic roseola presentation showing high fever followed by rash after defervescence with clinical photographs of the maculopapular rash. Panel D: Characteristic fifth disease appearance with slapped cheek erythema and lacy reticular body rash with epidemiologic implications highlighted. --- ### III. Viral Exanthems Measles (rubeola) has resurged in unvaccinated or under-vaccinated populations and presents with a distinctive prodrome and rash pattern. The prodrome is characterized by the three Cs: cough, coryza, and conjunctivitis, accompanied by high fever. Koplik spots, appearing as small white or bluish-white papules on the buccal mucosa opposite the molars, are pathognomonic when present but may be missed if not specifically sought during the first few days of illness. The maculopapular rash begins on the face and behind the ears, spreading cephalocaudally to involve the trunk and extremities, often becoming confluent. Complications include pneumonia (the most common cause of measles-related death), encephalitis, and subacute sclerosing panencephalitis developing years after acute infection. Rubella (German measles) is generally a mild illness but carries devastating consequences when infection occurs during pregnancy, causing congenital rubella syndrome with cataracts, cardiac defects (particularly patent ductus arteriosus and pulmonary stenosis), and sensorineural deafness. The postnatal infection presents with a pink maculopapular rash that begins on the face, spreads rapidly to the body, and resolves within three days, earning the name "three-day measles." Distinctive postauricular, suboccipital, and posterior cervical lymphadenopathy often precedes the rash and helps differentiate rubella from other viral exanthems. The importance of rubella lies primarily in prevention through MMR vaccination to achieve herd immunity and protect pregnant women from exposure. Varicella (chickenpox) produces one of the most recognizable childhood exanthems, with lesions classically described as "dewdrops on a rose petal" representing vesicles on an erythematous base. The rash begins on the face, scalp, and trunk before spreading centrifugally to the extremities, with lesions appearing in successive crops over three to five days resulting in simultaneous presence of macules, papules, vesicles, and crusted lesions. Pruritus is intense and leads to scratching that may cause secondary bacterial superinfection. Treatment is supportive for most immunocompetent children, with acyclovir reserved for adolescents, adults, and immunocompromised patients at higher risk for severe disease including varicella pneumonia and encephalitis. Hand-foot-mouth disease, caused primarily by coxsackievirus A16 and enterovirus 71, is highly contagious and common in daycare and preschool settings. The disease presents with fever, malaise, and decreased oral intake followed by vesicular lesions on the hands, feet, and oral mucosa (tongue, buccal mucosa, and posterior pharynx). Oral lesions may cause significant pain limiting oral intake, and maintaining hydration is the primary management concern. The illness typically resolves spontaneously within seven to ten days, though nail changes (onychomadesis) may occur weeks later. Outbreaks of enterovirus 71 in Asia have been associated with more severe neurologic complications including brainstem encephalitis, aseptic meningitis, and acute flaccid paralysis. Panel A: Measles clinical progression showing the three Cs prodrome, Koplik spots on buccal mucosa, and characteristic cephalocaudal rash spread. Panel B: Comparison of measles, rubella, and scarlet fever rash patterns with distinguishing clinical features. Panel C: Varicella lesion evolution from macule through vesicle to crusted stage with "dewdrop on rose petal" morphology demonstrated. Panel D: Hand-foot-mouth disease distribution showing typical vesicular lesions on palms, soles, and oral mucosa with close-up of oral ulcerations. --- ### IV. Bacterial Pharyngitis Group A streptococcal (GAS) pharyngitis peaks in school-age children between five and fifteen years and requires accurate diagnosis to prevent both overtreatment and the rare but serious complications of untreated infection. Clinical features supporting streptococcal etiology include fever, severe sore throat, tonsillar exudates, tender anterior cervical lymphadenopathy, palatal petechiae, and scarlatiniform rash. The Centor criteria (fever, tonsillar exudates, tender anterior lymphadenopathy, and absence of cough) and McIsaac modification adding age adjustment help identify patients warranting testing. Importantly, the presence of viral symptoms including rhinorrhea, cough, conjunctivitis, and hoarseness suggests viral pharyngitis and makes GAS unlikely. Diagnosis of streptococcal pharyngitis requires laboratory confirmation rather than clinical judgment alone, given the poor specificity of clinical findings. Rapid antigen detection tests are highly specific but have variable sensitivity, so a negative rapid test in children should be followed by throat culture for definitive diagnosis. Adults and adolescents with negative rapid tests generally do not require culture confirmation. Empiric treatment without testing is not recommended, as it leads to unnecessary antibiotic exposure for the majority of patients with viral pharyngitis. Testing asymptomatic contacts or treating carriers is generally not indicated except in outbreak settings or when the household contacts experience recurrent streptococcal infections. First-line treatment for confirmed streptococcal pharyngitis remains penicillin V or amoxicillin for ten days, with amoxicillin often preferred for children due to better taste and once-daily dosing options. Cephalosporins (cephalexin) are appropriate for patients with non-anaphylactic penicillin allergy, while azithromycin is reserved for those with severe penicillin allergy due to increasing resistance. Treatment shortens symptom duration by approximately one to two days, reduces contagiousness (allowing return to school after 24 hours of antibiotics), and prevents suppurative complications and acute rheumatic fever. Antibiotic therapy does not reliably prevent post-streptococcal glomerulonephritis, which develops regardless of treatment. Complications of streptococcal pharyngitis include both suppurative and non-suppurative sequelae. Suppurative complications include peritonsillar abscess ("quinsy") presenting with muffled voice, trismus, uvular deviation, and asymmetric tonsillar swelling; retropharyngeal abscess causing neck stiffness, stridor, and systemic toxicity; and cervical lymphadenitis. Non-suppurative complications include acute rheumatic fever, developing one to five weeks after pharyngitis and characterized by migratory polyarthritis, carditis, chorea, subcutaneous nodules, and erythema marginatum, and post-streptococcal glomerulonephritis presenting with hematuria, edema, and hypertension one to three weeks after pharyngitis or skin infection. Scarlet fever, while dramatic in appearance, is not a true complication but rather the consequence of streptococcal erythrogenic toxin production. Panel A: Clinical photograph of streptococcal pharyngitis showing tonsillar exudates, palatal petechiae, and anterior cervical lymphadenopathy with differential diagnosis considerations. Panel B: Diagnostic algorithm for pharyngitis incorporating Centor/McIsaac criteria, rapid testing, and culture indications. Panel C: Jones criteria for acute rheumatic fever diagnosis with major and minor criteria illustrated. Panel D: Comparison of suppurative complications including peritonsillar abscess, retropharyngeal abscess, and cervical lymphadenitis with anatomical diagrams. --- ### V. Otitis Media Acute otitis media (AOM) represents one of the most common diagnoses in pediatric practice, with peak incidence between six months and three years of age when eustachian tube anatomy and function predispose to middle ear infection. Risk factors include daycare attendance, bottle propping, exposure to tobacco smoke, pacifier use beyond six months, and craniofacial abnormalities. The predominant pathogens are Streptococcus pneumoniae, nontypeable Haemophilus influenzae, and Moraxella catarrhalis, with the relative contribution of each varying geographically and over time due to pneumococcal conjugate vaccine effects. Accurate diagnosis requires demonstration of middle ear effusion with signs of acute inflammation, distinguishing AOM from otitis media with effusion (OME), which lacks acute inflammatory signs. Pneumatic otoscopy revealing a bulging, immobile tympanic membrane with loss of normal landmarks is the gold standard for diagnosis. Supporting features include erythema of the tympanic membrane, otalgia, and otorrhea if perforation has occurred. Crying alone causes tympanic membrane erythema and is insufficient for diagnosis without other findings. The American Academy of Pediatrics diagnostic criteria require moderate to severe tympanic membrane bulging or new onset otorrhea, or mild bulging with recent symptom onset and otalgia or erythema. Management of AOM depends on age, severity, and laterality, with observation without antibiotics appropriate for select cases. Children under six months always receive antibiotics given the higher risk of serious bacterial infection. Children aged six months to two years with bilateral AOM or severe symptoms require antibiotics, while those with mild unilateral AOM may be observed with close follow-up. Children over two years with mild symptoms may be observed regardless of laterality if reliable follow-up can be ensured. When antibiotics are indicated, high-dose amoxicillin (80-90 mg/kg/day) is first-line therapy to overcome resistant pneumococcal strains. Amoxicillin-clavulanate or ceftriaxone is used for treatment failure or recent antibiotic exposure. Otitis media with effusion (OME) represents middle ear fluid without acute infection and commonly follows AOM or occurs with eustachian tube dysfunction from allergies or upper respiratory infections. Unlike AOM, OME does not require antibiotic treatment and typically resolves spontaneously within three months. The concern with persistent OME is conductive hearing loss that may impact speech and language development during critical periods. Management includes watchful waiting with repeat examination, hearing assessment if effusion persists beyond three months, and referral for tympanostomy tube placement if significant hearing loss or effusion beyond four to six months occurs. Complications of recurrent or chronic ear disease include tympanic membrane perforation, mastoiditis presenting with postauricular swelling and tenderness, and cholesteatoma requiring surgical intervention. Panel A: Otoscopic images comparing normal tympanic membrane, acute otitis media with bulging and erythema, and otitis media with effusion showing air-fluid level and retraction. Panel B: Treatment algorithm for acute otitis media based on age, severity, and laterality with antibiotic selection guidance. Panel C: Anatomical diagram of eustachian tube function in children versus adults explaining the predisposition to otitis media in young children. Panel D: Complications of otitis media including mastoiditis with postauricular swelling and cholesteatoma with CT imaging correlation. --- ### VI. Pneumonia The etiology of community-acquired pneumonia in children varies significantly by age, guiding empiric antibiotic selection. In neonates (birth to three weeks), pathogens reflect vertical transmission and include group B Streptococcus, gram-negative enteric organisms (Escherichia coli, Klebsiella), and Chlamydia trachomatis (typically presenting at two to three weeks with staccato cough and minimal fever). Infants one to three months continue to harbor these pathogens while also becoming susceptible to Streptococcus pneumoniae. Preschool children (three months to five years) are most commonly affected by viral pneumonia (RSV, influenza, parainfluenza, adenovirus) with S. pneumoniae as the primary bacterial cause. School-age children and adolescents increasingly contract Mycoplasma pneumoniae and Chlamydophila pneumoniae (atypical pathogens), though pneumococcus remains important. Clinical features of pneumonia include fever, cough, and tachypnea, with tachypnea being the most sensitive predictor of lower respiratory infection in children. The World Health Organization defines tachypnea using age-specific thresholds: greater than 60 breaths per minute for infants under two months, greater than 50 for infants two to twelve months, and greater than 40 for children one to five years. Additional findings include retractions, grunting, nasal flaring, decreased breath sounds, crackles, and dullness to percussion with lobar consolidation. Hypoxia (oxygen saturation below 90-92%) indicates severe disease requiring hospitalization. Extrapulmonary manifestations such as abdominal pain (lower lobe involvement) may confound the presentation. Diagnostic evaluation varies by setting and severity. Outpatient pneumonia in otherwise healthy children often requires only clinical diagnosis, with chest radiography adding cost without changing management in mild cases. Hospitalized patients warrant chest radiograph, blood culture, and consideration of viral testing to guide antibiotic therapy and isolation. Inflammatory markers (C-reactive protein, procalcitonin) may help distinguish bacterial from viral etiology but lack sufficient specificity for routine use. Pleural fluid analysis should be performed when effusion is present and accessible to identify complicated parapneumonic effusion or empyema requiring drainage. Empiric antibiotic treatment for outpatient preschool children typically consists of high-dose amoxicillin targeting S. pneumoniae. School-age children with suspected atypical pneumonia may be treated with a macrolide (azithromycin) alone or in combination with amoxicillin. Hospitalized children receive ampicillin or a third-generation cephalosporin (ceftriaxone, cefotaxime), with azithromycin added for suspected atypical coverage. Duration of therapy is typically five to ten days, with shorter courses supported by evidence for mild-moderate uncomplicated pneumonia. Follow-up chest radiograph is not routinely needed for uncomplicated cases but should be obtained at four to six weeks for lobar collapse, round pneumonia, or persistent symptoms to exclude underlying pathology. Panel A: Age-based distribution of pneumonia pathogens from neonates through adolescents with corresponding empiric antibiotic recommendations. Panel B: Clinical and radiographic features distinguishing lobar pneumonia, bronchopneumonia, and interstitial (atypical) pneumonia patterns. Panel C: Chest radiograph examples showing right middle lobe consolidation, round pneumonia, and parapneumonic effusion. Panel D: Algorithm for hospitalization decision-making in pediatric pneumonia incorporating oxygen saturation, age, and clinical appearance. --- ### VII. Urinary Tract Infections Urinary tract infection (UTI) is a common and important diagnosis in febrile infants and children, with particular significance due to the association with underlying urologic abnormalities and risk for renal scarring. Prevalence in febrile infants varies by age, sex, and circumcision status, with uncircumcised males having eight-fold higher risk in the first year of life compared to circumcised males. After infancy, UTI becomes more common in females due to shorter urethral length. Risk factors include vesicoureteral reflux, which may be present in up to 40% of children with first febrile UTI, anatomic abnormalities, constipation, and voiding dysfunction. Clinical presentation varies dramatically by age, making high clinical suspicion essential in young children. Neonates may present with sepsis, jaundice, poor feeding, and temperature instability without localizing symptoms. Infants present with fever, irritability, vomiting, and poor feeding. Toddlers may have fever, abdominal pain, and new-onset incontinence. Only older children reliably report classic dysuria, frequency, urgency, and suprapubic or flank pain. The absence of another source for fever should prompt UTI evaluation in infants and young children, particularly febrile infants under twenty-four months. Diagnostic confirmation requires both urinalysis and urine culture obtained by reliable methods before antibiotic treatment. Bag specimens are contaminated in up to 85% of cases and should only be used to exclude UTI when negative; positive results require confirmation by catheterization or suprapubic aspiration. Urinalysis findings suggesting UTI include pyuria (more than five white blood cells per high-power field), positive leukocyte esterase, positive nitrites (specific but insensitive as not all uropathogens reduce nitrate), and bacteriuria on microscopy. Culture thresholds for diagnosis are 50,000 colony-forming units per milliliter for catheterized specimens and 100,000 CFU/mL for clean-catch specimens, with lower thresholds considered in symptomatic patients. Treatment of UTI depends on age, clinical severity, and ability to tolerate oral antibiotics. Neonates and young infants with potential urosepsis require parenteral antibiotics covering gram-negative organisms (ampicillin plus gentamicin or a third-generation cephalosporin). Older infants and children with pyelonephritis may be treated orally if they appear well and can tolerate oral medications, with common choices including cephalexin, cefixime, or trimethoprim-sulfamethoxazole depending on local resistance patterns. Duration is typically seven to fourteen days for pyelonephritis and three to five days for cystitis in older children. Imaging with renal and bladder ultrasound is recommended after first febrile UTI in children aged two to twenty-four months, with voiding cystourethrogram reserved for abnormal ultrasound or recurrent UTI. Panel A: Algorithm for UTI evaluation in febrile infants based on age, sex, and circumcision status with pretest probability estimates. Panel B: Comparison of urine collection methods (clean catch, catheterization, suprapubic aspiration) with contamination rates and appropriate clinical use. Panel C: Urinalysis interpretation guide with sensitivity and specificity of individual components and combination findings. Panel D: Imaging strategy flowchart after first febrile UTI showing when to obtain ultrasound versus VCUG and expected findings. --- ### VIII. Meningitis Bacterial meningitis remains a life-threatening infection requiring rapid recognition and treatment, with age-dependent pathogen distribution guiding empiric therapy. Neonates are susceptible to group B Streptococcus (early-onset from maternal colonization or late-onset from horizontal transmission), Escherichia coli and other gram-negative enteric organisms, and Listeria monocytogenes. Beyond the neonatal period through age three months, these organisms persist while Streptococcus pneumoniae emerges. From three months through adolescence, S. pneumoniae and Neisseria meningitidis predominate, with Haemophilus influenzae type b now rare due to vaccination. Immunization has dramatically reduced bacterial meningitis incidence but has not eliminated it. Clinical presentation of meningitis varies by age, with classic meningeal signs often absent in young infants. Neonates present with nonspecific signs including temperature instability (fever or hypothermia), irritability, poor feeding, lethargy, and full or bulging fontanelle. Older infants may demonstrate irritability worsened by handling (paradoxical irritability), high-pitched cry, and bulging fontanelle but still lack neck stiffness. Classic meningeal signs including nuchal rigidity, Kernig sign (resistance to knee extension with hip flexed), and Brudzinski sign (hip flexion with passive neck flexion) become reliable only after eighteen months to two years. Altered mental status, seizures, and focal neurologic deficits may occur at any age. A petechial or purpuric rash strongly suggests meningococcal disease and constitutes a medical emergency. Cerebrospinal fluid analysis distinguishes bacterial from viral (aseptic) meningitis and guides treatment. Bacterial meningitis typically produces CSF with elevated white blood cells (often greater than 1000 cells per microliter) with neutrophil predominance, depressed glucose (less than 40 mg/dL or less than 50% of concurrent serum glucose), and elevated protein (greater than 100 mg/dL). Gram stain may identify organisms in 60-90% of untreated bacterial meningitis. Viral meningitis shows lymphocyte-predominant pleocytosis (typically 10-500 cells per microliter), normal to slightly low glucose, and mildly elevated protein. Bacterial antigen testing and multiplex PCR panels can aid identification, particularly when antibiotics were given before lumbar puncture. Traumatic lumbar puncture complicates interpretation and may require repeating the procedure or using correction formulas. Empiric antibiotic therapy must be initiated immediately upon clinical suspicion of bacterial meningitis, ideally after lumbar puncture but not delayed if LP is not immediately feasible. For neonates, ampicillin plus either gentamicin or cefotaxime covers group B Streptococcus, Listeria, and gram-negative organisms. For infants and children beyond three months, ceftriaxone plus vancomycin provides coverage for pneumococcus (including resistant strains) and meningococcus. Dexamethasone given before or with the first antibiotic dose reduces hearing loss in H. influenzae meningitis and possibly pneumococcal meningitis. Duration of therapy depends on the pathogen: seven days for N. meningitidis, ten to fourteen days for S. pneumoniae, and fourteen to twenty-one days for group B Streptococcus and gram-negative organisms. Panel A: Age-based distribution of bacterial meningitis pathogens with corresponding empiric antibiotic regimens. Panel B: Clinical photograph demonstrating examination for meningeal signs including Kernig and Brudzinski signs with technique descriptions. Panel C: CSF findings comparison table for bacterial versus viral meningitis with typical value ranges and interpretation guidance. Panel D: Meningococcal disease progression showing petechial rash evolution to purpura fulminans with immediate management priorities. --- ### IX. Serious Bacterial Infections Sepsis in children requires rapid recognition and aggressive management, with clinical presentation varying by age and underlying health status. The systemic inflammatory response syndrome (SIRS) criteria (temperature, heart rate, respiratory rate, and white blood cell abnormalities) help identify children with potential sepsis, though these criteria are neither sensitive nor specific in isolation. More important is clinical assessment for evidence of poor perfusion: altered mental status, prolonged capillary refill, mottled or cool extremities, weak pulses, tachycardia, and tachypnea. Temperature instability (hypothermia being as concerning as fever in neonates), feeding difficulty, and irritability may be the only early signs in young infants. Recognition of early sepsis before hypotension (compensated shock) is critical as pediatric patients maintain blood pressure until cardiovascular decompensation is imminent. Osteomyelitis in children most commonly affects the metaphysis of long bones, where sluggish blood flow in sinusoidal vessels predisposes to bacterial seeding during transient bacteremia. Staphylococcus aureus is the predominant pathogen across all ages, with Kingella kingae increasingly recognized in toddlers. Clinical presentation includes fever, localized bone pain with point tenderness, and refusal to bear weight or use the affected extremity. Laboratory findings reveal elevated inflammatory markers (CRP, ESR) and often leukocytosis. Plain radiographs may be normal early in the disease course, with lytic changes appearing only after ten to fourteen days. MRI is the most sensitive imaging modality and should be obtained when clinical suspicion is high. Treatment requires prolonged antibiotic therapy, initially intravenous with transition to oral when clinical improvement and inflammatory marker normalization allow, for a total duration of four to six weeks. Septic arthritis represents a surgical emergency due to the potential for rapid cartilage destruction and permanent joint damage. The hip and knee are most commonly affected, with S. aureus again the predominant pathogen. Presentation includes fever, joint swelling, warmth, and severe pain with passive range of motion, with the affected joint held in the position of maximal capsular relaxation (hip in flexion, abduction, and external rotation). The Kocher criteria (fever greater than 38.5 degrees Celsius, non-weight-bearing, ESR greater than 40 mm/hour, and WBC greater than 12,000 cells per microliter) help distinguish septic arthritis from transient synovitis, with all four criteria present yielding 99% probability of septic joint. Joint aspiration revealing purulent fluid with greater than 50,000 white blood cells per microliter, positive Gram stain, or positive culture confirms the diagnosis. Hip septic arthritis requires emergent surgical drainage, while other joints may be managed with repeated aspirations if accessible. Kawasaki disease is an acute febrile vasculitis of unknown etiology that primarily affects children under five years and requires timely recognition to prevent coronary artery aneurysms. The diagnosis is clinical, requiring fever for five or more days plus four of five criteria: bilateral nonexudative conjunctival injection, oral mucosal changes (strawberry tongue, cracked lips, erythema), polymorphous rash, extremity changes (erythema, edema, later desquamation), and cervical lymphadenopathy (usually unilateral, greater than 1.5 cm). Incomplete Kawasaki disease should be considered in children with prolonged fever and fewer than four criteria, particularly if inflammatory markers and echocardiographic findings support the diagnosis. Treatment with intravenous immunoglobulin (2 g/kg as single infusion) plus high-dose aspirin within ten days of fever onset reduces coronary aneurysm risk from 25% to approximately 4%. Echocardiography should be performed at diagnosis, two weeks, and six to eight weeks to assess coronary artery dimensions. Panel A: Clinical algorithm for pediatric sepsis recognition incorporating SIRS criteria, clinical perfusion assessment, and shock progression from compensated to decompensated. Panel B: MRI and plain radiograph comparison in osteomyelitis showing early MRI detection versus delayed radiographic changes. Panel C: Kocher criteria probability chart for septic arthritis versus transient synovitis with clinical decision guidance. Panel D: Complete Kawasaki disease clinical findings with photographs of conjunctival injection, strawberry tongue, rash, and extremity changes plus coronary artery aneurysm on echocardiography. --- ### X. Prevention The childhood immunization schedule represents one of the most effective public health interventions, preventing substantial morbidity and mortality from vaccine-preventable diseases. The schedule begins at birth with hepatitis B vaccine to prevent perinatal transmission, followed by combination vaccines at two, four, and six months targeting diphtheria, tetanus, pertussis, Haemophilus influenzae type b, polio, pneumococcus, and rotavirus. Live vaccines (measles-mumps-rubella, varicella) are administered beginning at twelve to fifteen months when maternal antibody interference diminishes. Booster doses at four to six years and adolescent vaccines (tetanus-diphtheria-pertussis, meningococcal, human papillomavirus) complete the recommended series. Annual influenza vaccination is recommended for all children aged six months and older. Special populations require modified vaccination approaches. Immunocompromised children should not receive live vaccines (MMR, varicella, live attenuated influenza, rotavirus) due to risk of vaccine-strain disease. Children with asplenia or functional asplenia (including sickle cell disease) require additional pneumococcal and meningococcal vaccinations for protection against encapsulated organisms. Premature infants should be vaccinated according to chronological age using full vaccine doses, with the exception that hepatitis B vaccination may be delayed in infants weighing less than 2000 grams born to hepatitis B surface antigen-negative mothers. Catch-up vaccination schedules allow completion of series for children who have missed vaccines, with minimum intervals between doses that must be maintained. Addressing vaccine hesitancy requires understanding parental concerns and providing evidence-based responses with empathy and respect. Common concerns include the debunked link between vaccines and autism (based on fraudulent research), fear of overwhelming the immune system with multiple vaccines (unfounded given the thousands of antigens encountered daily), and concerns about vaccine ingredients (present in trace amounts far below harmful levels). Effective communication strategies include presumptive language ("your child is due for vaccines today"), acknowledgment of concerns, sharing of personal vaccination decisions, and provision of credible resources. Documenting informed refusal and continuing to offer vaccines at subsequent visits maintains the relationship while respecting parental autonomy. Antimicrobial stewardship principles are essential for preserving antibiotic effectiveness and minimizing harm from unnecessary exposure. Antibiotics should be prescribed only when bacterial infection is confirmed or highly probable, with narrow-spectrum agents chosen when possible. Duration should be the shortest effective course supported by evidence. Common stewardship opportunities include avoiding antibiotics for viral upper respiratory infections, bronchiolitis, and viral pharyngitis; using watchful waiting for appropriate cases of acute otitis media; obtaining cultures before starting empiric therapy when feasible; and streamlining from broad-spectrum empiric therapy to narrow-spectrum directed therapy based on culture results. Education of families about the difference between viral and bacterial infections and the harms of unnecessary antibiotics supports these efforts. Panel A: Visual timeline of the childhood immunization schedule from birth through eighteen years with color-coded vaccine categories. Panel B: Comparison table of live versus inactivated vaccines with implications for immunocompromised patients. Panel C: Framework for addressing vaccine hesitancy with evidence-based responses to common concerns. Panel D: Antimicrobial stewardship decision points in common pediatric infections with appropriate versus inappropriate antibiotic prescribing scenarios. --- ## Summary - Febrile infants under 28 days require full sepsis evaluation including lumbar puncture and empiric antibiotics regardless of appearance - Infants 29-60 days with fever can be stratified using Rochester or Philadelphia criteria for low-risk identification - Viral upper respiratory infections resolve in 7-10 days with supportive care; antibiotics are not indicated - Streptococcal pharyngitis requires laboratory confirmation; treat with amoxicillin or penicillin for ten days - Acute otitis media treatment depends on age and severity; amoxicillin 80-90 mg/kg/day is first-line when antibiotics are indicated - Pneumonia pathogens vary by age; viral and S. pneumoniae predominate in young children while atypical coverage is added for school-age children - UTI in febrile infants requires catheterized specimen; renal ultrasound after first febrile UTI in children 2-24 months - Bacterial meningitis requires immediate empiric therapy with ceftriaxone plus vancomycin beyond three months of age - Kawasaki disease presents with fever greater than five days plus clinical criteria; IVIG plus aspirin prevents coronary aneurysms - Immunizations following the recommended schedule prevent substantial morbidity from vaccine-preventable diseases --- ## Key Terms | Term | Definition | |------|------------| | Febrile infant | Infant with temperature of 38 degrees Celsius (100.4 degrees Fahrenheit) or higher | | Centor criteria | Clinical prediction rule for streptococcal pharyngitis: fever, exudates, adenopathy, absence of cough | | Otitis media | Middle ear infection with bulging, immobile tympanic membrane and acute symptoms | | Urosepsis | Urinary tract infection with systemic manifestations of sepsis | | Meningismus | Clinical signs of meningeal irritation including nuchal rigidity, Kernig and Brudzinski signs | | Kawasaki disease | Acute febrile vasculitis affecting coronary arteries in young children | | Roseola | HHV-6 infection presenting with high fever followed by rash after defervescence | | HFMD | Hand-foot-mouth disease caused by coxsackievirus or enterovirus | --- *This content is subject to the [MIT License](https://opensource.org/licenses/MIT). © 2024–2026 Hibbert School of Medicine.*