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.


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 of pneumonia may include some or all of the following:

Bacterial PneumoniaViral PneumoniaAtypical Pneumonia
FeverFeverFever, often low-grade
Shaking chillsChillsChills
Cough that produces green, yellow, or rust-colored mucusDry coughCoughing; may be violent at times; produces white mucus
Chest painHeadachePossible nausea or vomiting
Profuse sweatingMuscle painWeakness
Bluish color of the nails or lips due to diminished oxygen in the bloodBluish color of the nails or lips due to diminished oxygen in the blood 
Confused mental stateWeakness 


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 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.

If you are diagnosed with pneumonia, follow your doctor's instructions .


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:
    • People over aged 65, or those who have a chronic illness, such as ]]>diabetes]]> or ]]>sickle-cell disease]]>
    • Children under two years old

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.