Atypical pneumonia is a lung infection.

“Typical pneumonia” is a severe illness. It is usually caused by bacteria, such as Streptococcus pneumoniae, Haemophilus influenzae or Klebsiella pneumoniae . Typical pneumonia tends to strike older individuals, especially those with heart or lung conditions.

In contrast, atypical pneumonia tends to be a milder illness. It is caused by a different assortment of bacteria or viruses, and it usually strikes healthy young people.

All types of pneumonia are potentially serious conditions that require care from your doctor.

The Lungs (Cut-away View)

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Atypical pneumonia is usually caused by:

  • Bacteria
    • Mycoplasma pneumoniae
    • Chlamydia bacteria
    • Coxiella burnetii
    • Legionella
  • Viruses

Risk Factors

The following factors increase your chance of developing atypical pneumonia:

  • Being a child, adolescent, or young adult
  • Living in closed communities, such as dormitories in boarding schools or colleges, and military barracks
  • Cigarette smoking
  • Lung disease
  • Weakened immune system


If you experience any of these symptoms, do not assume the cause is due to pneumonia. These symptoms may be caused by other, less serious health conditions.

  • Fever (mild)
  • Enlarged lymph nodes
  • Red eyes
  • Chills
  • Cough, often dry
  • Sore throat
  • Phlegm (sputum) production
  • Muscle aches and pains
  • Decreased appetite
  • Headache
  • Chest pain
  • Shortness of breath
  • Fast breathing
  • Intense fatigue
  • Weakness
  • Vomiting
  • Diarrhea
  • Skin rash


Your doctor will ask about your symptoms and medical history, and do a physical exam. Tests may include the following:

  • Chest x-ray —a test that uses radiation to take a picture of structures inside the chest; may reveal pneumonia
  • Blood tests—testing your white blood cells can determine whether you are experiencing a bacterial or a viral infection. Other blood tests can identify the presence of certain bacteria or viruses.
  • Blood cultures—bacteria or viruses may be grown from samples of your blood
  • Sputum test—if you are coughing up sputum, you may be asked to collect some in a sterile container for testing; can reveal what type of bacteria is causing your illness


Talk with your doctor about the best treatment plan for you. Treatment options include the following:


Usually, atypical pneumonia due to bacteria can be treated with oral antibiotics at home. However, more severe pneumonia may require intravenous antibiotics in the hospital. Some of the antibiotics used to treat atypical pneumonia include erythromycin , azithromycin , and clarithromycin .

Viral pneumonia will not respond to antibiotic treatment.


If you are severely ill from pneumonia, you may need extra oxygen.

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


To help reduce your chances of getting pneumonia, take the following steps:

  • Use good hand-washing techniques.
  • Avoid contact with other ill people.
  • Get treatment for your chronic conditions.