Aetiology of CAP in children 2 months or older

Note: Viruses are the most common cause of CAP in children 2 months or older.

Viruses are the most common cause of community-acquired pneumonia (CAP) in children 2 months or older. Children with chronic suppurative lung disease (eg bronchiectasis, cystic fibrosis) may be colonised with Pseudomonas aeruginosa. For management of children with cystic fibrosis, see Airway infection and antibiotic therapy in cystic fibrosis; for causes, clinical features, diagnosis and general management of children with bronchiectasis, see Bronchiectasis.

For the aetiology of CAP in children 2 months or older, see Aetiology of community-acquired pneumonia (CAP) in children 2 months or older.

Table 1. Aetiology of community-acquired pneumonia (CAP) in children 2 months or older
Benet, 2017 Kohns Vasconcelos, 2023 Oishi, 2021 Smyrnaios, 2023 Zhu, 2022
Pathogen	Details
Respiratory viruses (eg adenovirus, coronavirus, hMPV, influenza virus, parainfluenza virus, RSV)	Viruses make up to 70% of CAP in children 2 months or older.
Streptococcus pneumoniae	Most common bacterial cause of CAP in children 2 months or older. For directed therapy regimens, see Streptococcus pneumoniae (pneumococcal) pneumonia.
Staphylococcus aureus	An important cause of complicated high-severity CAP (including necrotising pneumonia, which can also be caused by more common pathogens). Parapneumonic effusion and thoracic empyema and lung abscess are complications of staphylococcal pneumonia in children. For features of staphylococcal pneumonia and directed therapy regimens, see Staphylococcal pneumonia.
Chlamydophila (Chlamydia) pneumoniae or Mycoplasma pneumoniaeArnold, 2023 Biondi, 2014 Gardiner, 2015 Williams, 2017	C. pneumoniae or M. pneumoniae can cause CAP, especially in school-aged children; however, the benefit of antibiotic therapy is uncertain. For directed therapy regimens, see Mycoplasma pneumoniae pneumonia and Chlamydophila (Chlamydia) species pneumonia.
Nontypeable Haemophilus influenzae	H. influenzae type b (Hib) has become a less common bacterial cause of CAP since vaccination against Hib has increased; however, this has not decreased the number of cases of CAP caused by nontypeable Haemophilus influenzae. See the Australian Immunisation Handbook for more information.
Streptococcus pyogenes (group A streptococcus)	For pneumonia suspected or confirmed to be caused by S. pyogenes, manage as for complicated S. pyogenes bacteraemia; see Streptococcus pyogenes bloodstream infections, including toxic shock syndrome.
Pseudomonas aeruginosa	Children with chronic suppurative lung disease (eg bronchiectasis, cystic fibrosis) may be colonised with P. aeruginosa. For directed therapy regimens, see Pseudomonas aeruginosa pneumonia.
Burkholderia pseudomallei	B. pseudomallei is a rare but important cause of CAP in children in tropical regions of Australia [NB1]. Empirical therapy is only needed for children with high-severity CAP requiring intensive care support in the wet season. For directed therapy regimens, see Melioidosis.
Mycobacterium tuberculosis	Consider tuberculosis in high-risk patient groups (eg people from high-prevalence regions, household contacts), and children with an undiagnosed febrile or wasting illness, or a persistent cough.
Bordetella pertussis	Causes pertussis but is a rare cause of CAP in young children. Suspect pertussis in children who present with paroxysmal cough associated with cyanosis or apnoea.
Note: hMPV = human metapneumovirus; RSV = respiratory syncytial virus. NB1: Tropical regions of Australia refer to regions north of 20°S latitude. This includes areas of Queensland north of Mackay, the Northern Territory north of Tennant Creek, and Western Australia north of Port Hedland.