Medical Specialties: Emergency medicine, Internal medicine, Pulmonology

Clinical Definition

Pneumonia is a potentially fatal illness that causes consolidation of the affected segment of the lung and inflammation of the lung parenchyma. Pneumonia may be lobular or segmental. Bacteria and viruses are the most common causative agents, although fungi and aspiration of food can also lead to pneumonia. The infection is characterized by excess mucus, fatigue and shortness of breath.

In Our Own Words

There are many different kinds of pneumonia, a respiratory infection that causes inflammation in the airways and lung tissue. The small air sacs inside the lungs, known as alveoli, become filled with fluid and pus. One or both lungs may be affected.


Causes of pneumonia include viruses, bacteria and fungi. In addition, accidental inhalation of food or chemicals can lead to pneumonia. Pneumonia may be acute and develop suddenly or keep reoccurring, which is considered chronic pneumonia. Symptoms may vary from mild to severe. Pneumonia is a common complication of the flu. 

Relevant Conditions
  • Bacterial Pneumonia
  • Pneumococcal pneumonia
  • Viral Pneumonia
  • Aspiration Pneumonia
Common Types
  • Cold
  • Flu
Side Effects
  • Cough
  • Fever
  • Shortness of breath
  • Wheezing
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