The most common causative organisms are (often intracellular living) bacteria: ;Chlamydia pneumoniae: Mild form of pneumonia with relatively mild symptoms. ;Chlamydia psittaci: Causes psittacosis. ;Coxiella burnetii: Causes Q fever. ;Francisella tularensis: Causes tularemia. ;Legionella pneumophila: Causes a severe form of pneumonia with a relatively high mortality rate, known as legionellosis or Legionnaires' disease. ;Mycoplasma pneumoniae: Usually occurs in younger age groups and may be associated with neurological and systemic (e.g. rashes) symptoms.<unk>  can also have a fungal, protozoan or viral cause.In the past, most organisms were difficult to culture. However, newer techniques aid in the definitive identification of the pathogen, which may lead to more individualized treatment plans. Viral Known viral causes of<unk>  include respiratory syncytial virus (RSV), influenza A and B, parainfluenza, adenovirus, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), COVID-19 and measles.
Atypical pneumonia
Fungal pneumonia
Lobar pneumonia
Dust pneumonia
Viral pneumonia
Bacterial pneumonia
Lipid pneumonia
Lung abscess