Etiology
Bacterial
Viral
Mycoplasma
Age
Any
<2 years
5–15 years
Season
All year
Winter
All year
Presentation
Sudden
Variable
Insidious
Fever
High
Variable
Low
Tachypnea
Common
Common
Infrequent
Coughing
+
++
+++
Related symptoms
Chest pain
Acute rhinitis, conjunctivitis
Pharyngitis
Coinfection with different pathogens is possible. The most frequent combinations are RSV or influenza virus with Streptococcus pneumoniae, in 30% of the cases, and Mycoplasma pneumoniae with Streptococcus pneumoniae or Chlamydia pneumoniae in 15% of cases (Table 31.2).
Table 31.2
Etiological agents according to age
RN | 1–3 months | 4–24 months | Preschool | School | |
|---|---|---|---|---|---|
Virus | |||||
RSV | + | +++ | ++++ | ++ | − |
ADV | − | + | ++ | + | − |
Influenza | − | − | + | ++ | +++ |
Parainfluenza | − | + | + | + | − |
Metapneumovirus | − | + | + | + | − |
Bacteria | |||||
Streptococcus pneumoniae | + | + | ++ | ++++ | ++++ |
Mycoplasma pneumoniae | − | − | + | ++ | ++++ |
Haemophilus influenzae | − | + | + | − | − |
Staphylococcus aureus | + | + | + | + | + |
Streptococcus agalactiae | +++ | + | − | − | − |
Escherichia coli and other gram-negative bacilli | ++ | + | − | − | − |
Chlamydia trachomatis | − | − | − | + | + |
Chlamydia pneumoniae | − | − | + | + | ++ |
Streptococcus pyogenes | − | − | − | + | + |
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