Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs (alveoli)—associated with fever, chest symptoms, and a lack of air space (consolidation) on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes. Infectious agents include: bacteria, viruses, fungi, and parasites.
Typical symptoms include cough, chest pain, fever, and difficulty breathing. Diagnostic tools include x-rays and examination of thesputum. Vaccines to prevent certain types of pneumonia are available. Treatment depends on the underlying cause. Presumed bacterial pneumonia is treated with antibiotics.