Mycoplasma, Chlamydia and Legionella are the usual organisms considered to be the etiologic agents of ‘atypical’ pneumonia. Other microorganisms such as bacteria, viruses, parasites, fungi and mycobacteria can also present with atypical pneumonia manifestations. Outbreaks and isolated cases of respiratory viruses with atypical pneumonia presentations have been reported among immunocompetent and immunosuppressed patients. Severe infections due to these respiratory viruses alone or as a concomitant bacterial or viral infection have been observed. Additionally, in endemic areas, certain zoonotic infections may present as atypical pneumonia.