(Community-Acquired Pneumonia; CAP; Pneumonitis; Bronchopneumonia)  

Pronounced: Noo-MO-NEE-yah

by Michelle Badash, MS

En Español (Spanish Version)More InDepth Information on This Condition

* Definition  

Pneumonia is an infection of the lungs. It affects the lower respiratory tract. This includes small bronchi (airways) and air sacs in the lungs.
Development of Pneumonia in the Air Sacs of the Lungs
pneumonia lung fluid
The normal exchange of gases is interrupted by the build up of fluids.

© 2009 Nucleus Medical Art, Inc.

* Causes  

There are three main causes:

  • Bacterial pneumonia—caused by bacteria, most commonly Streptococcus pneumoniae
  • Viral pneumonia—caused by a virus (responsible for half of all pneumonias)
  • Atypical bacterial pneumonia—often called "walking pneumonia but can cause a more serious or potentially fatal pneumonia; caused by:
    • Mycoplasmahis
    • Chlamydias
    • Other tiny infectious agents that have traits of both bacteria and viruses

Other causes of pneumonia include:

Pneumonias are sometimes described by where it was acquired and how you were exposed to it:

  • Community-acquired pneumonia—acquired in the community (eg, at school, work, gym)
  • Nosocomial pneumonia—acquired during a hospitalization
    • Can be very dangerous, especially for patients on a ventilator
  • Aspiration pneumonia—happens when a foreign matter (often stomach content) is inhaled


lung aspiration food
© 2009 Nucleus Medical Art, Inc.

* Risk Factors  

Factors that increase your chance of pneumonia include:

  • Age: 65 or older
  • Flu or other respiratory illness
  • Chronic illness, such as heart or lung disease
  • Stroke (aspiration pneumonia due to difficult swallowing)
  • Weakened immune system caused by AIDS or chemotherapy treatment
  • Chronic bronchitis
  • Malnutrition
  • Pregnancy
  • Infants and very young children
  • Alcohol or drug abuse
  • Smoking
  • Chronic exposure to certain chemicals (eg, work in construction or agriculture)

* Symptoms  

Symptoms of pneumonia may include some or all of the following:

Bacterial Pneumonia

Viral Pneumonia

Atypical Pneumonia



Fever, often low-grade

Shaking chills



Cough that produces green, yellow, or rust-colored mucus

Dry cough

Coughing; may be violent at times; produces white mucus

Chest pain


Possible nausea or vomiting

Profuse sweating

Muscle pain


Bluish color of the nails or lips due to diminished oxygen in the blood

Bluish color of the nails or lips due to diminished oxygen in the blood


Confused mental state



* Diagnosis  

The doctor will ask about your symptoms and medical history. A physical exam will be done. Diagnosis is based on symptoms and listening to your chest. Tests may include:

  • Chest x-ray—a test that uses radiation to take pictures of structures inside the body, in this case the chest
  • CT scan—a type of x-ray that uses a computer to make pictures of structures inside the chest
  • Blood tests
  • Bronchoscopy—direct examination of airways
  • Sputum culture—testing mucus coughed up from deep in the lungs
  • Pulse oximetry—measures the amount of oxygen in the blood
  • Arterial blood gas—measures oxygen, carbon dioxide, and acid in the blood

* Treatment  

Treatment of pneumonia depends on:

  • Type of pneumonia
  • Severity of symptoms
  • Other factors

Common methods of treatment include:

Bacterial Pneumonia  

  • Antibiotics

Viral Pneumonia  

  • Rest and fluids
  • Antiviral medicines—may be prescribed for young children and patients with weakened immune systems
  • Note: Antibiotics are ineffective for treating viral pneumonia

Atypical Pneumonia  

  • Antibiotics


  • Over-the-counter medicines to reduce fever and aches, and soothe cough
  • Hospitalization, for people with very severe symptoms

It is very important to take the medicine as prescribed. Stopping medicine early may cause a relapse. It may also create a strain of drug resistant bacteria.

* Prevention  

Certain vaccines may prevent pneumonia:

  • Flu shot—for people at high risk, particularly the elderly, because pneumonia may be a complication of the flu
  • Pneumococcal vaccine—recommended for:

Other preventive measures include:

  • Avoid smoking. Smoke weakens the lungs' resistance to infection.
  • Avoid close contact with people who have the cold or flu.
  • Wash hands often. This is very important when coming in contact with infected people.
  • Protect yourself on jobs that affect the lungs.
  • Eat a healthy diet.
  • Get adequate rest.
  • Exercise regularly.

Last reviewed February 2009 by Rosalyn Carson-DeWitt, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

Copyright © 2009 EBSCO Publishing. All rights reserved.

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