Description
The 'atypical' pathogens are important causes of pneumonia, causing illness ranging from mild to life-threatening. The most common atypical pathogens are Mycoplasma pneumoniae and Chlamydia pneumoniae; others include Legionella species, Chlamydia psittaci and viruses such as influenza, adenovirus and respiratory syncytial virus. Infection rates for these agents are difficult to determine because many clinicians and investigators do not routinely test for them, but reported rates are in the range of up to 8% (for C pneumoniae) and 15% to 20% (M pneumoniae) of all cases of pneumonia. Diagnostic testing is very difficult because most of these agents cannot be easily cultured. Diagnosis relies on either high acute antibody titres (quickly available but not very accurate) or paired serology samples (more accurate but requires at least a week). While rapid identification using automated polymerase chain reaction testing may be possible in the future, current management is based largely on empirical treatment.