Pronounced: new-mo-SIS-tis new-MOAN-ya
Pneumocystis pneumonia (PCP) is a form of pneumonia. It affects people who have a weakened immune system. PCP is the most common serious infection among people with AIDS.
The Lungs (Cut-away View)
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PCP is caused by a fungus. Most believe that the fungus is spread in the air, but it is not clear if the fungus 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, the fungus can spread and cause a lung infection.
A weakened immune system can put you at risk for PCP. The immune system may be weakened in people who:
Symptoms of PCP usually develop over the course of a few weeks or months. The main symptoms of PCP are:
See your doctor immediately if you have any these symptoms.
Your doctor will ask about your symptoms and medical history. To confirm PCP, a sample of mucus from your lungs will be examined under the microscope. Your doctor will collect samples by giving you either:
Treatment depends on the severity of the infection.
PCP infections can cause damage to your lungs and affect your overall health. Preventing a PCP infection is an important first step. A healthy immune system is the best prevention for PCP. See your doctor as recommended to help monitor your immune system. If you have HIV, follow your treatment program to keep your immune system healthy. This will help prevent a PCP infection.
If you are at risk for PCP, your doctor may recommend that you take antibiotic medication to prevent getting it. Take preventative medication as recommended, do not skip doses. PCP prevention with medication may be recommended if:
Talk to your doctor about a pneumococcal vaccine. This only protects you from a different kind of pneumonia. It will not prevent you from getting PCP.
AIDS Info—National Institutes of Health
Centers for Disease Control and Prevention
Canadian Public Health Association
The Lung Association
Pneumocystis pneumonia. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/fungal/diseases/pneumocystis-pneumonia/index.html. Accessed January 29, 2021.
Pneumocystis pneumonia (PCP). EBSCO Dynamed website. Available at: http://www.dynamed.com/topics/dmp~AN~T114345/Pneumocystis-pneumonia-PCP . Accessed January 29, 2021.
Pneumocystis jirovecii pneumonia. Merck Manual Professional Version website. Available at:
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Accessed January 29, 2021.
Last reviewed March 2020 by EBSCO Medical Review Board David L. Horn, MD, FACP