Pneumocystis pneumonia (PCP) is a lung infection. It is a form of pneumonia. PCP is caused by a fungus called Pneumocystis jiroveci . This used to be called Pneumocystis carinii .

This infection affects people who have a weakened immune system. It is the most common serious infection among people with AIDS]]> .

PCP can be prevented.

The Lungs (Cut-away View)

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Most scientists believe that P jiroveci is spread in the air. It is not clear if it lives in soil or elsewhere. In healthy people, the fungus can exist in the lungs without causing pneumonia. However, in people who have a weakened immune system, PCP may cause a lung infection.

Risk Factors

People who are at increased risk for PCP include those who:

  • Have AIDS
  • Have cancer]]>
  • Are getting treatment for cancer



Symptoms of PCP usually develop over the course of a few weeks or months. The main symptoms of PCP are:

  • Shortness of breath
  • Fever
  • Dry cough
  • Tightness in the chest
  • Weakness

See your doctor immediately if you experience these symptoms.


A sample of your sputum is examined under the microscope. Sputum is mucus material from your lungs. It is produced when you cough. Your doctor will collect samples by giving you either:

  • A vapor treatment to make you cough
  • A bronchoscopy]]> —an instrument is inserted into your airway



If you get PCP, your treatment will depend on how serious the infection is. If you have a mild case, you will be given medication in pill form. If you have a severe case, you will probably be treated in the hospital. Medication will be given by IV.

There are several drugs used to treat PCP:

Most of these treatments have side effects. You and your doctor should this into account when considering options.

Even when treatment is given for PCP, the death rate is 15% to 20%. It’s best to avoid getting PCP in the first place.



PCP can be prevented. If you are at risk for PCP, your doctor may recommend that you take medicine to prevent getting it. In general, for those with HIV infection, preventing PCP with medication is recommended if your CD4 cell count falls below 200. Other conditions, like having a temperature above 100˚F that lasts for more than two weeks, or getting a fungal infection in your mouth or throat, are reasons to start preventive therapy.

Some of the same drugs used to treat an infection can be taken regularly to prevent the infection:

  • Dapsone
  • Atovaquone
  • Pentamidine aerosol

If you get PCP once, you are more likely to get it again. Each time you get it, it causes damage to your lungs. Your body can suffer side effects from the drugs.

You may have heard of a pneumonia vaccine]]> . This only protects you from a different kind of pneumonia. It will not prevent you from getting PCP. Quitting smoking can also help you avoid getting PCP.