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Lung Disease & Respiratory Health Center

Bacterial Pneumonia

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Bacterial Pneumonia Causes

  • Most pneumonia is caused by bacteria or a virus. Pneumonia from any cause can occur at any age, but people in certain age groups are at higher risk for certain types of pneumonia.
  • The most common cause of bacterial pneumonia is Streptococcus pneumoniae.Haemophilus influenzae, Chlamydia trachomatis, Mycoplasma pneumoniae, and Legionella pneumophila are some other major bacteria that cause pneumonia.
  • The most common way you catch pneumonia is to breathe infected air droplets from someone who has pneumonia. Another cause is an improperly cleaned air conditioner. Yet another source of infection in your lungs is spread by an infection from somewhere else in your body, such as your kidney. Your risk of catching pneumonia is determined by the specific bacteria, virus, or fungus, the number of organisms you inhale, and your body's ability to fight infections.
  • You do not catch pneumonia by not dressing properly for cold weather or by being caught in the rain.

Other Causes of Pneumonia:

If you inhale toxic materials, you can injure your lungs and cause chemical pneumonia. Fungus also can cause pneumonia. In certain areas of the United States, specific fungi are well known. Coccidioidomycosis causes a pneumonia called "San Joaquin fever" or "Valley fever" in the desert regions of California. Histoplasmosis and blastomycosis cause pneumonias in the Ohio and Mississippi river valleys.

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