Pneumonia is a breathing (respiratory) condition in which there is an infection of the lung.
This article covers pneumonia in people who have not recently been in the hospital or another health care facility (nursing home or rehab facility). This type of pneumonia is called community-acquired pneumonia, or CAP.
Bronchopneumonia; Community-acquired pneumonia; CAP
Causes, incidence, and risk factors
Pneumonia is a common illness that affects millions of people each year in the United States. Germs called bacteria, viruses, and fungi may cause pneumonia.
Ways you can get pneumonia include:
Bacteria and viruses living in your nose, sinuses, or mouth may spread to your lungs.
You may breathe some of these germs directly into your lungs.
You breathe in (inhale) food, liquids, vomit, or fluids from the mouth into your lungs (aspiration pneumonia)
Pneumonia caused by bacteria tends to be the most serious kind. In adults, bacteria are the most common cause of pneumonia.
The most common pneumonia-causing germ in adults is Streptococcus pneumoniae (pneumococcus).
Sharp or stabbing chest pain that gets worse when you breathe deeply or cough
White nail syndrome, or leukonychia
Signs and tests
If you have pneumonia, you may be working hard to breathe, or breathing fast.
The health care provider will hear crackles or abnormal breath sounds when listening to your chest with a stethoscope. Other abnormal breathing sounds may also be heard through the stethoscope or by tapping on your chest wall (percussion).
The health care provider will likely order a chest x-ray if pneumonia is suspected.
Niederman M. In the clinic. Community-acquired pneumonia. Ann Intern Med. 2009;151(7).
Torres A, Menandez R, Wunderink R. Pyogenic bacterial pneumonia and lung abscess. In: Mason RJ, Broaddus VC, Martin TR, et al. Murray & Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 32.
Denis Hadjiliadis, MD, Assistant Professor of Medicine, Division of Pulmonary, Allergy and Critical Care. University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.