Inflammation of large airways of the lung
Pneumonia must be excluded by clinical evaluation or by CXR
If all 5 are negative pneumonia is safely excluded:
HR >100
RR >24
Temperature >38 (100.4)
Exam findings consistent with focal consolidation, egophony, or fremitus
Age >64yr
Viruses are most common cause
Influenza, paraflu, RSV, coronavirus, adenovirus, rhinovirus
Bacterial cause occurs in <10% of cases
Mycoplasma, C. pneumoniae, pertussis (1% of<unk>  cases)
Influenza, paraflu, RSV, coronavirus, adenovirus, rhinovirus
Mycoplasma, C. pneumoniae, pertussis (1% of<unk>  cases)
Acute bronchitis
URI 
Atypical pneumonia
LRI 
Croup
Influenza
Bronchiectasis
Allergy