Condition

Community-Acquired Pneumonia in Children

Editors: Christina R. Hermos MD, MS; Zbigniew Fedorowicz PhD, MSc, DPH, BDS, LDSRCS; Stacey Valentine MD, MPH

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Background Information

Description

  • Community-acquired pneumonia is a lower respiratory tract infection typically associated with fever, respiratory symptoms, and evidence of parenchymal involvement by either physical examination or presence of infiltrates on chest x-ray.
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Definitions

  • Community-acquired pneumonia refers to an acute pulmonary infection in a previously healthy individual acquired in the community.
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  • Walking pneumonia typically describes school-aged children and young adults with clinical and radiographic evidence of pneumonia, but with mild symptoms.
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  • Hospital-acquired pneumonia or nosocomial pneumonia develops after 48 hours of admission.
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Epidemiology

Incidence/Prevalence

  • The incidence of pneumonia in higher-income countries is about 30-40 cases per 1,000 children < 5 years old.
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  • STUDY SUMMARY
    overall incidence of community-acquired pneumonia requiring hospitalization from 2010 to 2012 in the United States reported to be 15.7 per 10,000 children with highest incidence in children < 2 years old
    POPULATION-BASED SURVEILLANCE: N Engl J Med 2015 Feb 26;372(9):835

  • The incidence of pediatric pneumonia in 2010 was estimated to be 0.22 episodes per child-year worldwide and 0.015 episodes per child-year in high-income countries (J Glob Health 2013 Jun;3(1):010401).
  • Reduced incidence of pneumococcal pneumonia is reported after implementation of childhood vaccination.
    • STUDY SUMMARY
      annual hospitalization rates for pneumococcal pneumonia appear to have decreased in children since introduction of 13-valent pneumococcal conjugate vaccine in the United States
      COHORT STUDY: Clin Infect Dis 2017 Jun 15;64(12):1699

    • STUDY SUMMARY
      pneumococcal conjugate vaccine associated with 16% overall decrease in community-acquired pneumonia (CAP) and decreased pneumococcal CAP in children presenting to emergency departments
      COHORT STUDY: Clin Infect Dis 2014 Apr;58(7):918

    • STUDY SUMMARY
      10- and 13-valent pneumococcal vaccine associated with reduced hospitalization and mortality in children < 5 years old in Latin America
      SYSTEMATIC REVIEW: PLoS One 2016;11(12):e0166736

Risk Factors

  • Risk factors for community acquired pneumonia in children include:
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    • Patient characteristics and underlying medical conditions, such as:
      • Age < 5 years
      • Congenital heart disease
      • Bronchopulmonary dysplasia and chronic lung disease
      • Diabetes mellitus
      • Cystic fibrosis
      • Asthma
      • Sickle cell disease
      • Neuromuscular disorders
      • Gastrointestinal disorders, such as gastroesophageal reflux and tracheoesophageal fistula
      • Congenital and acquired immunodeficiency
    • Socioeconomic and environmental factors, such as:
      • Active or passive exposure to cigarette smoke
      • Lack of breastfeeding
      • Malnutrition
      • Lower socioeconomic status
      • Low maternal education level
      • Poor access to care
      • Indoor air pollution
      • Alcohol, drugs, and cigarette use in teens
  • Risk factors for severe or complicated pneumonia in children include:
    • Age < 2 years
    • Incomplete or inadequate pneumococcal and Haemophilus influenzae type B vaccination
    • Immunodeficiency
    • Malnutrition
    • Chronic lung diseases
    • Cystic congenital thoracic malformations
    • Foreign body aspiration
    • Reference - Lancet 2020 Sep 12;396(10253):786
  • Factors associated with decreased risk of pneumonia in children:
    • STUDY SUMMARY
      breastfeeding associated with decreased pneumonia prevalence and all-cause mortality in children < 24 months old
      SYSTEMATIC REVIEW: BMC Public Health 2013;13 Suppl 3:S18

Etiology and Pathogenesis

Causes

  • The identification of the causative organism in routine clinical settings can be challenging.
    • Viral and bacterial causes are not easily distinguished by clinical or radiological features.
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    • Obtaining appropriate samples from the lower respiratory tract in children can be difficult.
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    • Blood cultures are rarely obtained in the community setting, and when they are taken in the hospital, they have a low yield.
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    • If nasal specimens are used, distinguishing between colonizing and pathogenic bacteria may not be possible.
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  • The implementation of conjugate vaccines against Pneumococcus and Haemophilus influenzae type B has significantly reduced the incidence of pneumonia in children caused by those pathogens.
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  • The most common causes of community acquired pneumonia in children:
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    • Aged < 5 years include respiratory viruses, including respiratory syncytial virus, and Streptococcus pneumoniae
    • Aged ≥ 5 years include respiratory viruses, Mycoplasma pneumoniae, and S. pneumoniae
    table iconTable 1. Causes of Pneumonia in Children
    Table 1: Causes of Pneumonia in Children
    Frequency Bacterial Viral
    Common
    • Streptococcus pneumoniae
    • Haemophilus influenzae (where vaccine is available, type B is uncommon, and nontypeable is common)
    • Bordetella pertussis (young infants)
    • Mycoplasma pneumoniae
    • Group B streptococci (young infants)
    • Mycobacterium tuberculosis (not common in the United States)
    • Influenza virus types A and B
    • Respiratory syncytial virus
    • Parainfluenza virus
    • Human metapneumovirus
    • Adenovirus
    • Rhinovirus
    Less Common
    • Streptococcus pyogenes
    • Anaerobes (Streptococcus milleri, Peptostreptococcus)
    • Haemophilus influenza nontype B
    • Klebsiella pneumoniae
    • Escherichia coli
    • Listeria monocytogenes (beyond the newborn period)
    • Neisseria meningitides (often group Y)
    • Legionella
    • Burkholderia pseudomallei
    • Francisella tularensis
    • Brucella abortus
    • Leptospira
    • Chlamydia psittaci
    • Coxiella burnetii
    • Varicella zoster virus
    • Coronaviruses
    • Enteroviruses (coxsackievirus and echovirus)
    • Cytomegalovirus
    • Epstein-Barr virus
    • Mumps virus
    • Bocaviruses
    • Polyomaviruses
    • Measles virus
    • Hantavirus
    Reference - Pediatr Clin North Am 2013 Apr;60(2):437, Pediatr Radiol 2017 Oct;47(11):1392.
  • COVID-19 does not typically present as community-acquired pneumonia in immunocompetent children.
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  • Prevalence of pathogens reported in cohort study of 2,638 children hospitalized with pneumonia to 3 United States hospitals from 2010 to 2012:
    • Viral pathogens detected in 66%, including:
      • Respiratory syncytial virus in 28%
      • Human rhinovirus in 27%
      • Human metapneumovirus in 13%
      • Adenovirus in 11%
      • Parainfluenza in 7%
      • Influenza in 7%
      • Coronavirus in 5%
    • Bacterial pathogens detected in 8%, including:
      • M. pneumoniae in 8%
      • S. pneumoniae in 4%
      • Staphylococcus aureus in 1%
      • Group A Streptococcus in < 1%
    • Mixed viral-bacterial infection detected in 7%
    • Reference - EPIC study (N Engl J Med 2015 Feb 26;372(9):835)
  • STUDY SUMMARY
    respiratory syncytial virus, adenovirus, and human metapneumovirus more common in children < 5 years old, and M. pneumoniae more common in older children in the United States with community acquired pneumonia
    COHORT STUDY: N Engl J Med 2015 Feb 26;372(9):835

  • Pathogens associated with pneumonia in children ≤ 5 years old in low-income countries are generally similar to those in high-income countries (Clin Infect Dis 2017 Aug 15;65(4):604).
  • STUDY SUMMARY
    in severely malnourished children, Klebsiella species is a common cause of bacterial pneumonia in addition to species that frequently cause pneumonia in all children (such as S. aureus and S. pneumoniae)
    SYSTEMATIC REVIEW: Trop Med Int Health 2009 Oct;14(10):1173

Pathogenesis

  • Pneumonia is an infection of the alveoli that occurs when the immune system cannot clear pathogens from the lower airway and alveoli.
    • Systemic inflammation may also occur due to local inflammatory factors and cytokines causing secondary symptoms including fever, chills, and fatigue.
    • Pus in the parenchyma leads to decreased lung compliance and shunting, making breathing more difficult, and exacerbates hypoxia and tachypnea.
    • PubMed30955516The Medical clinics of North AmericaMed Clin North Am201905011033487-501487Reference - Med Clin North Am 2019 May;103(3):487
  • Mechanism of infection:
    • Exposure of the nearly-sterile lower respiratory tract to pathogens via aspiration or inhalation is the usual route of infection. The route of infection may vary by infecting organism.
      • Aspiration of oral flora (as with aspiration pneumonia) is common with Streptococcus pneumoniae, Haemophilus influenzae, and gram-negative rods.
      • Inhalation of pathogen-containing droplets or aerosols is common with Mycoplasma pneumoniae, Chlamydia pneumoniae, and viruses. Microparticles must be small (< 5 micrometers) to allow transit into the lower airways and evasion of the immune system.
    • Progression to pneumonia relies on the failure of immune mechanisms to clear the pathogen, which may be influenced by:
      • The size of inoculum of the pathogen
      • The volume and frequency of aspirations
      • The presence of virulence factors in the pathogens which overcome immune response
      • Comorbidities associated with weakened immune response, such as chronic malnutrition
    • PubMed30955516The Medical clinics of North AmericaMed Clin North Am201905011033487-501487References - Med Clin North Am 2019 May;103(3):487, Emerg Med Clin North Am 2018 Nov;36(4):665
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