Atypical Pneumonia

Written by Elly Dock and Elizabeth Boskey, PhD | Published on July 25, 2012
Medically Reviewed by George Krucik, MD

Atypical Pneumonia


Atypical pneumonia refers to pneumonia (a long infection) that is not caused by the bacteria that cause the “typical pneumonia.” Typical pneumonia tends to be more serious than atypical pneumonia.

This type of pneumonia is also sometimes referred to as “walking pneumonia,” in reference to the fact that it is less severe than other forms of lung infection.

What Are The Types of Atypical Pneumonia?

Atypical pneumonia is caused by one of three types of bacteria:

  • Chlamydophila pneumoniae
  • Legionella pneumophila
  • Mycoplasma pneumoniae

Mycoplasma Pneumonia

This condition tends to affect people under the age of 40. It is responsible for 15 to 50 percent of diagnosed pneumonia in school-aged children and adults.

This condition most often occurs in people working or living in heavily populated areas such as schools, homeless shelters, and group homes. However, many individuals are diagnosed without any specific risk factors.

Legionella Pneumonia

This condition causes two to six percent of pneumonia cases. It has a higher death rate than other types of atypical pneumonia.

Risk factors for this type of pneumonia include:

  • smoking
  • older age
  • a weak immune system
  • other chronic illness

It is usually caused by breathing air exhaled by an infected individual.

Chlamydophila Pneumonia

This type of pneumonia occurs throughout the year. It is responsible for five to 15 percent of all pneumonia cases. It presents mild symptoms and rarely causes death.

This condition is most common in school-age children. Scientists estimate that half the adults in the United States have had this pneumonia by age 20.

What Are The Symptoms Of Atypical Pneumonia?

The symptoms associated with atypical pneumonia are generally mild. They may include:

  • confusion (legionella)
  • chills
  • cough
  • diarrhea (legionella)
  • headache
  • fever
  • muscle aches
  • muscle stiffness
  • loss of appetite
  • rash (mycoplasma)
  • shortness of breath
  • rapid breathing

How Is Atypical Pneumonia Diagnosed?

Your doctor will perform a physical exam. You may also need a chest X-ray for diagnosis. A chest X-ray can distinguish between pneumonia and other respiratory illness, such as acute bronchitis.

Depending on your symptoms, you may need other tests. Some tests use to diagnose pneumonia include:

  • sputum culture
  • throat swab
  • complete blood count (CBC)
  • blood tests for specific antibodies
  • blood cultures

How Is Atypical Pneumonia Treated?

Antibiotics are used to treat the bacteria causing your condition. For mild cases, you will take antibiotics by mouth. In more severe cases, you may get them intravenously.

Some people with severe atypical pneumonia may need supplemental oxygen.

What Can Be Expected in the Long Term?

Most individuals with mycoplasma or chlamydophila pneumonia recover completely with antibiotics. However, it is important to take your entire prescription. If antibiotics are stopped early, there is a risk the infection may return.

If atypical pneumonia is not treated in a timely manner, complications may result.

Most atypical pneumonia causes only mild symptoms. However, legionella pneumonia can be very severe or even fatal.

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