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What Is Pneumonia?

Wednesday, April 17, 2013 - 14:00
Contributors to this article: 

Archie Wilson MD
J T Macfarlane MD
Guy Slowik FRCS

Pneumonia is an inflammation or infection of the lungs most commonly caused by a bacteria or virus. Pneumonia can also be caused by inhaling vomit or other foreign substances.

In all cases, the lungs' air sacs fill with pus , mucous, and other liquids and cannot function properly. This means oxygen cannot reach the blood and the cells of the body.

Types of pneumonia

Most pneumonias are caused by bacterial infections.

  • The most common infectious cause of pneumonia in the United States is the bacteria Streptococcus pneumoniae.
  • Other bacteria, as well as certain viruses, may also cause pneumonia. Since these infections may not cause all of the classic pneumonia symptoms, they are often called "atypical pneumonias."
  • Aspiration (or inhalation) pneumonia is a swelling and irritation of the lungs caused by breathing in vomit, fumes from such chemicals as bug sprays, pool cleaners, gasoline, or other substances. This kind of pneumonia cannot be spread to other people.

Nice To Know:

Pneumonia can also be defined by how much of the lung is involved.

  • In lobar pneumonia, one section (lobe) of a lung is affected.
  • In bronchial pneumonia (or bronchopneumonia), patches throughout both lungs are affected.

Facts about Pneumonia:

  • Pneumonia is a serious illness that affects one out of every 100 people each year.
  • Pneumonia can be caused by bacteria or viruses, or by inhalation of vomit or certain chemicals.


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