Table 1.

Classification of pneumonia.

Classification	Description/comments
A. By Location 1. Community-acquired pneumonia 2. Hospital-acquired pneumonia 3. Ventilator-acquired pneumonia	Infection acquired in the community Infection acquired following > 48 h stay in hospital or in someone recently discharged from hospital (within 7 days) Infection acquired by patient on ICU and mechanically ventilated for > 48 h
B. By Immune status 1. Immunocompetent 2. Immunocompromised	No immune dysfunction Immune dysfunction present– different definitions described, wide range in degree of immune dysfunction
C. By Microbiology 1. Viral 2. Bacterial 3. Fungal 4. Mycobacterial 5. Parasitic	This classification relies upon definitive microbiology which is usually unavailable at the time of first presentation, and may remain elusive even after investigation