Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
About Pneumocystis Infections
Pneumocystis jirovecii is a fungus that is common throughout the world. Many people have been exposed to it as children. Some people have the fungus in their lungs. If you are healthy, it usually will not make you sick. But it can make you sick if you have a weakened immune system, for example if you:
- Have HIV
- Have an autoimmune disease
- Have cancer
- Have a chronic (long-lasting) lung disease
- Had an organ or bone marrow transplant
- Take medicines which weaken your immune system, such as chemotherapy and steroids
Pneumocystis jirovecii can spread from person to person through the air. You can spread it to others even if it isn't making you sick.
The most common type of infection that Pneumocystis jirovecii causes is pneumocystis pneumonia (PCP). Pneumonia is an infection in one or both of the lungs. It causes the air sacs of the lungs to fill up with fluid or pus.
The symptoms of PCP can develop over several days or weeks. They may include:
- Fever
- Cough
- Trouble breathing
- Chest pain
- Chills
- Fatigue
Contact your healthcare provider if you have symptoms that you think are related to PCP. Since PCP can be life-threatening, it's important to get early treatment.
To find out if you have PCP, your provider will take a sample of fluid or tissue from your lungs. You may cough up the sample (called sputum), have fluid collected during a bronchoalveolar lavage, or have tissue taken with a biopsy. They will send the sample to the lab to check for Pneumocystis.
The treatment for PCP is with antibiotics, either by mouth or intravenously (by IV). You need to take them for about 3 weeks. If you have a severe case of PCP, you might need treatment in the hospital.
There is no vaccine to prevent PCP. Some people who are at high risk of getting PCP may need to take antibiotics to prevent it.
Centers for Disease Control and Prevention
It sits within Infections, Lungs and Breathing and Immune System.
The lead U.S. institute for this subject is the National Institute of Allergy and Infectious Diseases.
When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.
Research on Pneumocystis Infections
118 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.
What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.
Research currently under way
- TMP-SMX for Non-HIV PCP: A Prospective Multicenter StudySecond Affiliated Hospital, School of Medicine, Zhejiang University
- Derivation and Validation of the Fungal Pneumonia Assessment and Likelihood Predictor ScoreAzienda Ospedaliero-Universitaria Careggi
- Patient-Centered Practical Vaccine Talk For Busy CliniciansUniversity of Massachusetts, Worcester
- Low- vs Standard-Dose TMP-SMX for Prevention of Pneumocystis Pneumonia After Kidney TransplantationAnhui Provincial Hospital
- Optimizing the Diagnosis of Pneumocystis in Immunocompromised PatientsAssistance Publique - Hôpitaux de Paris
- Short-term Steroid Therapy in Patients With P. Jirovecii Pneumonia Due to HIV / AIDSCentro de Investigación en. Enfermedades Infecciosas, Mexico
Research already completed
- New Techniques for Using a Saline Wash as a Diagnostic Tool for Pneumocystis PneumoniaNational Institute of Allergy and Infectious Diseases (NIAID)
- Pneumocystis Pneumonia Diagnosis in HIV- PatientsRennes University Hospital
- Study of Rezafungin Compared to Standard Antimicrobial Regimen for Prevention of Invasive Fungal Diseases in Adults Undergoing Allogeneic Blood and Marrow TransplantationMundipharma Research Limited
- Performance Evaluation of the Fujifilm Wako Beta-D-glucan Technique in the Diagnosis of Major Invasive Fungal Infections (IFI)Central Hospital, Nancy, France
- Prevalence and Pathogenesis of Lung Disease in a Large HIV Cohort-coordinating CenterUniversity of Pittsburgh
- Pneumocystis in Patients Over 75 YearCentre Hospitalier Universitaire de Nīmes
Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.
Where to read more
Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.
Start Here
- Pneumocystis Pneumonia BasicsCenters for Disease Control and Prevention
- Pneumonia in People with a Weakened Immune SystemMerck & Co., Inc.
Clinical Trials
- ClinicalTrials.gov: Pneumocystis InfectionsNational Institutes of Health
Medical subject headings
Clinicians and researchers index this subject under Pneumocystis Infections. These are the terms to use when searching medical literature.
This page is built from the MedlinePlus health topic record for Pneumocystis Infections, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.