February 9, 2016
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Pneumonia Facts (cont.)

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What causes pneumonia? Is pneumonia contagious?

Streptococcus pneumoniae, a type of bacteria, is the most common cause of pneumonia. Legionella pneumophila is the bacterial type that causes the pneumonia known as Legionnaires' disease. Other bacteria types that can cause pneumonia include the bacteria that cause so-called "atypical" pneumonia, Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumonia.

The most common cause of viral pneumonia in adults is the influenza virus. A number of different respiratory viruses cause pneumonia in children, such as respiratory syncytial virus (RSV). While viral pneumonia tends to be less severe than bacterial pneumonia, there is a risk of developing secondary bacterial pneumonia when viral pneumonia is present. Other virus types that can cause pneumonia include measles and varicella (chickenpox) viruses. Rarely, certain viruses may develop lethal pneumonias such as SARS (severe acute respiratory syndrome) or MERS (Middle East respiratory syndrome); both diseases are caused by different coronaviruses.

Fungi that cause pneumonia include Cryptococcus, Histoplasma, and Coccidioides. In most cases, these organisms don't cause illness, but they can cause pneumonia in some people. Fungal infections are most common in those with weakened immune systems due to HIV/AIDS or those taking medications that suppress immune function. Another infection that is considered a fungal type of pneumonia is Pneumocystis jiroveci, formerly known as Pneumocystis carinii. This organism became known as a frequent cause of pneumonia in patients with HIV/AIDS.

What are risk factors for pneumonia?

There are a number of factors that increase the risk of developing pneumonia. These include

  • a weakened immune system, either due to disease such as HIV/AIDS or cancer, or to medications that suppress immune function;
  • infants and children 2 years of age or younger;
  • age 65 and older;
  • having a chronic disease such as cystic fibrosis, COPD, sickle cell anemia, asthma, heart disease, or diabetes;
  • swallowing or coughing problems, as may occur following stroke or other brain injury;
  • being a patient in an intensive-care unit of a hospital, particularly if on ventilator support;
  • malnutrition;
  • cigarette smoking.
Medically Reviewed by a Doctor on 5/4/2015

Source: MedicineNet.com

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