TABLE 1.

Most common pathogens implicated in lower respiratory tract syndromes and their relative contributionsa

Disease and pathogen% of cases
Acute bronchitis
    Respiratory virusesb90
    Bordetella pertussis-Bordetella parapertussis5-10c
    Mycoplasma pneumoniae5-10c
    Chlamydia pneumoniae5-10c
Community-acquired pneumonia
    Streptococcus pneumoniae66
    Haemophilus influenzae1-12
    Legionella species2-15
    Mycoplasma pneumoniae2-14
    Klebsiella species3-14
    Enteric gram-negative bacilli6-9
    Staphylococcus aureus3-14
    Chlamydia species5-15
    Influenza virus5-12
    Hantaviruses<1-2
    Other viruses<1-12
    Mycobacterium tuberculosis<1-10
    Moraxella catarrhalis<1-2
    Unknown23-49
Hospital-acquired pneumonia
    Gram-negative bacilli
        Pseudomonas aeruginosa16
        Enterobacter species11
        Klebsiella pneumoniae7
        Other enteric gram-negative bacilli9
        Acinetobacter3
        Legionella species0-2
        Haemophilus influenzae0-2
        Other0-10
    Gram-positive cocci
        Staphylococcus aureus17
        Streptococcus pneumoniae2-20
        Other2-5
    Anaerobes10-20
    Fungi0-10
    Mixed13-54
  • a The information in this table is compiled from references 3, 10, 19, 20, 23, and 25.

  • b Influenza A virus, Influenza B virus, parainfluenza virus type 3, respiratory syncytial virus, coronavirus, adenovirus, and rhinovirus.

  • c The values represent the collective contribution of all four pathogens listed.