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Lung Disease & Respiratory Health Center

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Pneumonia - Cause

Viruses, bacteria, a fungus, or (in rare cases) parasites or other organisms can cause pneumonia.

In people who have impaired immune systems, pneumonia may be caused by other organisms, including some forms of fungi, such as Pneumocystis jiroveci (formerly called Pneumocystis carinii). This fungus frequently causes pneumonia in people who have AIDS. Some doctors may suggest an HIV test if they think that Pneumocystis jiroveci is causing the pneumonia.

Recommended Related to Lung Disease/Respiratory Problems

Understanding Bronchitis -- Diagnosis and Treatment

Tests are usually unnecessary in the case of acute bronchitis, as the disease is usually easy to detect through your description of symptoms and a physical exam. The doctor will simply use a stethoscope to listen for the rattling sound in your lungs' upper airways that typically accompanies the problem. In cases of chronic bronchitis, the doctor will likely get an X-ray of your chest to check the extent of the lung damage, as well as pulmonary function tests to measure how well your lungs are working...

Read the Understanding Bronchitis -- Diagnosis and Treatment article > >

How do you get pneumonia?

You may get pneumonia:

  • After you breathe infected air particles into your lungs.
  • After you breathe certain bacteria from your nose and throat into your lungs. This generally occurs during sleep.
  • During or after a viral upper respiratory infection, such as a cold or influenza (flu).
  • As a complication of a viral illness, such as measles or chickenpox.
  • If you breathe large amounts of food, gastric juices from the stomach, or vomit into the lungs (aspiration pneumonia). This can happen when you have had a medical condition that affects your ability to swallow, such as a seizure or a stroke.

A healthy person's nose and throat often contain bacteria or viruses that cause pneumonia. Pneumonia can develop when these organisms spread to your lungs while your lungs are more likely to be infected. Examples of times when this can happen are during or soon after a cold or if you have a long-term (chronic) illness, such as chronic obstructive pulmonary disease (COPD).

You can get pneumonia in your daily life, such as at school or work (community-associated pneumonia) or when you are in a hospital or nursing home (healthcare-associated pneumonia). Treatment may differ in healthcare-associated pneumonia, because bacteria causing the infection in hospitals may be different from those causing it in the community. This topic focuses on community-associated pneumonia.

WebMD Medical Reference from Healthwise

Last Updated: September 09, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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