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Chest infections - adult - Background information
Acute bronchitis

  • Viral infection is widely reported to account for most cases of acute bronchitis [Alberta Medical Association, 2006; Braman, 2006]. However, the proportions of viral and bacterial causes of acute bronchitis are unclear from the limited available evidence. This uncertainty results from:
    • The high proportion of people in whom no viral or bacterial pathogen can be identified, despite thorough investigation.
    • The presence of commensal bacteria isolated from the upper respiratory tract that may not or may not have a pathogenic role in a particular infection.
  • Two small prospective studies (n = 316 and n = 80) examined the pathological causes of acute bronchitis in people that had no co–morbid conditions [Macfarlane et al, 2001; Creer et al, 2006]. In both studies no pathogen was identified in a significant proportion of people. There were significant differences in the proportion of different pathogens reported in each study but overall, it can be concluded that:
    • Viral infections are the most commonly identified cause of acute bronchitis.
    • A significant minority of identified causes are bacterial.
    • Of the bacterial causes Streptococcus pneumoniae and Haemophilus influenzae were the most commonly identified.
    • The atypical bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae were identified in a small proportion of people.

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